• 1  -  CONTENTS
• Background
• Comparative Table
• ETCHING WITHOUT ACID - A brief History of electrolyic etch
• What is Galv-Etch ?
• Advantages of galv-etch
• Equipment Guide
• Preparation
• Procedure - tray system
• Vertical Tank system
• Galv-On semi-dry method
• TIMES AND TESTS - calculating etching time
• Galvanoplasty and plating
• Precautions
• 2  -  BORDEAUX ETCH --------
• The dangers of ferric chloride
• A passive electrolytic process
• Disposal of chemicals
• Grounding without wax
• GROUNDING WITHOUT WAX - Ink ground
• Sugar lift with ink ground
• TINTING WITHOUT ROSIN - Fractint
• CLEANING WITHOUT SOLVENTS - Cooking oil
• Vegetable cleaning agent
• CONCLUSIONS
• Notes and references
• Related web sites
• APPENDICES
• A - Electro-etching in 1855
• B - First Patent 1840
• Untitled

GREEN  PRINTS

A HANDBOOK ON SOME NEW METHODS FOR SAFE INTAGLIO ETCHING AND METAL PLATE PRINTMAKING

Cedric Green FRSA

ECOTECH DESIGN -SHEFFIELD

Copyright © Cedric Green 1998 -2004 fifteenth edition February 2004

All prints illustrated are by the author. Above: "Antarctic" collage of printed galv-etched plates 80 x 80 cms

Published by Ecotech Design 26 Botanical Road, Sheffield S11 8RP Printed in France

ACKNOWLEDGMENTS

This booklet is intended primarily for printmakers with some experience of producing prints from metal plates -copper, zinc or steel. It assumes a reader with a basic knowledge of the traditional processes of etching, and like me, with a feeling of dissatisfaction with the toxicity and general unpleasantness of many of the processes involved, in particular the use of acid mordants and strong solvents.

It was written to amplify articles I wrote for Printmaking Today published in Spring 1998, 1999 and 2002 (1). I am grateful to the editors, Rosemary Simmons and Anne Desmet, for encouraging me to write about my personal experience and search for safer integrated methods for producing etchings, and the revival of 19th century electrolytic methods. The discipline of having to put it into writing stimulated a certain rigour in recording what I was doing, and led to finding new and interesting expressive possibilities. The response I received to the first article put me in touch with many printmakers who shared my concerns.

At the same time I was persuaded by Geffrey Green to make the results of my researches freely and widely available by putting them on the Internet, and I am very grateful for his work in creating the original website (whose address is given below). I want to thank Tim Healey for the time he spent answering my questions about the chemistry of Bordeaux etch, and his advice on the dangers of etching zinc plates in ferric chloride.

Ad Stijnman kindly supplied me with background information and samples of vegetable cleaning agent (VCA). Thanks too for encouragement and comments from Nik Semenoff, who first published an article on electroetching in 1991 (18) and researched a new mordant for aluminium and zinc similar to Bordeaux Etch, which was published at the same time as my first article (16). Keith Howard has tried the techniques with his students and I am grateful for his appreciative and helpful comments. I acknowledge with thanks the information supplied by Prior and Co. in Sheffield about their equipment for industrial electrolytic etched marking. Lastly I'd like to thank those printmakers who freely supplied me with information on their methods.

Cedric Green, August 1999

"Bêlèterie", 24300 St.Front-la-Rivière, Nontron, FRANCE. telephone: +33 (0)5 53 56 19 76 email: cwbg@club-internet.fr Websites: www.greenart.info  http://perso.club-internet.fr/gravert/galvetch/

CONTENTS

BACKGROUND

COMPARATIVE TABLE

ETCHING WITHOUT ACID

A brief history of electrolytic methods 11

WHAT IS GALV-ETCH ? 15

the electrolytic process 15  electrical units and ohms law 16  advantages of galv-etch over acids 17

EQUIPMENT GUIDE -WHAT TO BUY 20

Power supplies 20 chemicals and materials 25 preparation of the electrolyte 26 plate contacts 26 backplate contacts 27 cathode grid 27 flat tray for galv-etching line or tint 28 vertical tank 29 supporting a plate in a vertical tank 29

BASIC PROCEDURE IN GALV-ETCHING 31

using a standard tray and grid system 31 open bite or galvanoplasty in a flat tray 32 etching a plate in a vertical tank 33 deep etch and open bite 33

GALV-ON SEMI DRY METHOD 34

needled lines or tint with galv-on 36  TIMES AND TESTS 38

calculating the time to etch 38 the effect of voltage and amperage 40 galv-etching very large plates 42 special effects 44 galvanoplasty or galv-plating 46 precautions in using galv-etch 48

BORDEAUX ETCH 50 the dangers of ferric chloride 50 etching safely with copper sulphate 51 the chemistry of Bordeaux etch 52 A 'passive' electrolytic process 53 disposal of used Bordeaux etch 56

GROUNDING WITHOUT WAX 57

Relief printing ink ground 57 Ink hard ground 57 graining sugar lift 58 soft ground 59

TINTING WITHOUT ROSIN 60

fractint 60 galv-etching fractint 61 special effects of fractint 62 variations and refinements 63

CLEANING WITHOUT SOLVENTS 64

cleaning with cooking oil 64 vegetable cleaning agent 64 proofing galv-etched plates 66

CONCLUSIONS 67

NOTES AND REFERENCES

RELATED INTERNET WEB SITES 70

APPENDIX A : ELECTRO-ETCHING (1855) 73

APPENDIX B -FIRST PATENT 1840 76

INDEX 79

BACKGROUND

After years of working with traditional methods for making and proofing intaglio plates, and suffering all kinds of ill effects -sore eyes, eczema, asthma, sore throat, depression -I began to worry about the long term effects of the chemicals and processes on my health. Finally I was provoked by reading Tim Challis' "Print Safe" (2) to try replacing every toxic, unpleasant chemical or process, to make the whole physical process of making prints less of a tedious chore and more of an enjoyable creative process to match the pleasure of seeing the results coming off the press.

In particular, I'd been seriously inhibited about using the techniques that produced the results I liked best -deep etch with large areas of open bite, embossing, combinations of intaglio and relief -because of the prodigious quantities of acid used, and hours spent over zinc plates in ferric chloride brushing away noxious bubbles and removing the iron crust produced .

In short, over a period of years starting in 1992, thanks to articles in Printmaking Today (12, 13, 14, 15, 17), research into the history of electrolytic methods in the 19th century, contacts with other printmakers, advice from chemists and learning about some of the older methods using by commercial printing works, I gradually reformed all my practices and found safe substitutes for the methods that were clearly the most objectionable.

An important personal objective was to use inexpensive generic materials that are locally made or easily obtainable, and to avoid expensive, patented, registered or commercialized processes and products, and to look into the basis of some of these to find the generic or public domain process or chemical upon which they are based. In this area I made some interesting discoveries in the field of 19th century electrolytic etching methods that had been recently 'rediscovered', and patented, claiming that they were a new application. (see Appendix A -Electro-Etching 1855).

The alternative methods are not simply straight replacements that are cleaner and safer, but some of them can produce results and effects not possible with the original traditional methods, and the creative exploration of these is what makes them exciting to use. Also there is a kind of interdependence between them, for instance, electrolytic galvetching processes make possible new grounding materials that cannot be used with acids, and which themselves allow galv-etch to produce effects not possible with traditional grounds. The galv-on method gives effects and textures that are a rich addition to the range available to printmakers. Bordeaux etch for zinc and steel plates can also produce the same effects as galv-on used as a "passive" electrolytic process. Plating and creating new plates by galvanoplasty extend the range of possibilities still further.

The results to date of this empirical and theoretical research are summarized in the table on the next page, and then are described in detail later.

Details of prints from plates produced by the techniques that will be described

COMPARATIVE TABLE

TRADITIONAL ILL EFFECTS & SUBSTITUTE METHOD DANGERS (3) METHOD.

Etching copper plates: Nitrogen dioxide Electrolytic processes: nitric acid, hydrochloric poisoning, damage to galvanography (galvacid, Dutch mordant, eyes, lungs, nasal etch and galv-on for ferric chloride. membranes, skin etching). Etching zinc plates: damage. 'Bordeaux etch' electronitric, ferric chloride. chemical solution for

zinc and steel plates.

Hard, soft ground: Smoked turpentine based wax and asphaltum grounds; turpentine based wax and grease Irritation of mucous membranes, Nausea, headaches, toxic or carcinogenic fumes when heated, depression of central nervous system.

Insulating ink ground: relief printing ink applied by soft roller after drying as hard ground -before drying as soft ground.

Aquatint: powdered pine Rosin dust allergy, toxic Fractint -grounding rosin; powdered rosin fumes, with relief printing ink, asphaltum carcinogenic asphaltum produced in press.

fumes. Headaches, skin and eye irritation.

Stopping out: methanol See above for Ethanol (ethyl alcohol) (methylated spirit) methanol. based varnish: shellac based varnish. flakes dissolved in

rubbing or industrial ethyl alcohol.

Cleaning of varnish or ground: methanol, turpentine, naphtha (white spirit, turpentine substitute).

Irritation of mucous membranes, depression of central nervous system, skin damage; suspected kidney damage.

Ethanol: ethyl alcohol for cleaning varnish, ink ground or fractint. Vegetable Cleaning Agent (VCA) for ink .

Cleaning inked plates or See above for VCA or vegetable tools: turpentine, turpentine and naphtha cooking oil -followed naphtha (white spirit). by mild household

detergent. Ethanol for dried ink. Acetone for hardened ink.

ETCHING WITHOUT ACID

A brief history of electrolytic methods

Galvanism, or chemically produced electricity, was accidentally discovered by Luigi Galvani in 1789 who was doing experiments on frog's legs and found that muscles twitched when touched by two different metals in contact, a phenomenon he attributed to a fluid in organic tissue. Soon after that Alexandre Volta showed that it was due to a direct electric current, and built a 'galvanic battery' formed by alternating zinc and copper plates separated by fabric soaked in an acidic solution (5). In 1834 Michael Faraday postulated his Laws of Electrolysis (6). Smee and Daniell invented improved versions of galvanic cells, using a copper plate suspended in copper sulphate and a zinc plate in salt or sulphuric acid with a permeable plaster of paris partition between them. Thomas Spencer found that copper was deposited on the cathode or ‘negative metal’ and the zinc pole was etched. He and John Wilson were granted a patent in 1840 for "Engraving Metals by Voltaic Electricity" (see Appendix B for text of patent). These discoveries were immediately utilized to make printing plates, reproduce seals and plate small objects by the process that became known as ‘Electrotyping’.

Illustration by Thomas Spencer of his apparatus for creating the printing plate from which this illustration was printed in 1841 (20).

It was soon found that applying a direct current from a galvanic cell to a separate ‘cell’ containing a couple of parallel metal plates in a metallic salt solution (the electrolyte) dissolved metal from the anode (+ve) and deposited metal on the cathode (-ve). This is explained by the fact that an electrolyte, consisting of positive and negative ‘ions’ will conduct a direct electrical current, which carries the ions to the plate of the opposite polarity. In a copper sulphate solution the positive copper ions collect on the negative copper plate, and negative sulphate ions react with the bare metal of the copper anode -etch it in fact and create new copper sulphate. Thus the electrolyte stays at the same concentration, creating the illusion that copper particles are transferred from one plate to the other -a common fallacy.

The process of electrotyping become very widely used for creating printing plates, plating metal objects, decorating silverware and marking cutlery. In 1852 Charles V Walker documented and described all the processes that were currently known in his book Electrotype Manipulation, which went through 29 editions by 1859 and was also published in the USA (7). Part II included detailed descriptions of a patented process called 'Electro-Etching', and another called 'Electrotint' (see Appendix A for excerpts). The word 'Galvanography’ was synonymous with 'Electrotyping', basically meaning a plate made by depositing metal over a mould, a process which is called 'galvanoplasty'', but other processes of etching or plating, which used the same electrolytic principles and equipment were included in the original meaning. The term 'Galvanography’ was used to distinguish the graphic use of the Electrotyping process from the industrial use or the production of text type plates. The French name for the Electrotype process is 'galvanotypie' and a plate made by the process was called a 'galvano'.

After the invention of photography in 1839, there was international competition to find ways of making permanent ink prints of photographs, and many of the methods used electrolytic processes in one way or another. The earliest attempts, by Alfred Donne in 1839, and Joseph Berres in 1840 started with a daguerreotype, which was a photograph on a silvered copper plate, which was plated and then etched (8). But the Austrian, Paul Pretsch took a different approach and patented a process called 'photo-galvanography'', in which he began with a photographically exposed dichromated-gelatine mould which was made to reticulate, from which he produced a copper intaglio plate by galvanoplasty. He formed a company in London to produce the first commercially printed photographs called "Photographic Art Treasures" in 1856 (9).

Photograph reproduced on the title page of “Photographic Art Treasures” published by the photogalvanographic company of Paul Pretsch. The earliest printed photographic reproductions in England.

Electrolytic processes were much used in France for intaglio platemaking in the nineteenth century, particularly by the firm of Goupil & Cie, publishers of Fine Art reproductions. They used a process between photogravure and Pretsch's photo-galvanography, but kept the exact process a closely guarded secret (10). Early Ordnance Survey Map plates were produced by a special application of galvanography originally used by Spencer.

In the 1962 S W Hayter described the electrolytic process of depositing metal into lines drawn through a ground on a metal plate that he had developed and used at Atelier17 in Paris before the war (22). In industry electrolytic processes were used very widely, mainly for plating and protecting metal. Anodising was developed as a process for protecting aluminium. In 1943 a US company called Lectroetch adapted the Electro-Etching process to marking metals of all kinds, and is still supplying equipment and materials for the purpose. Many other companies have started to provide the same service, and electroetching became well enough known for artists who were interested to learn about it.

Commercial electrotyping and printing block making plant. 1 -cleaning tank. 2 -rectifier. 3 control unit. 4 electroplating tank. 5 anode rod. 6 -plate rod (cathode).

In Canada Nik Semenoff and Christine Christos carried out research into electro-etching in 1989, and published a paper in Leonardo, an art journal in 1991, detailing the method for artists, the equipment required, its advantages regarding safety. (18). In Sweden Ole Larsen developed electrolytic processes, and one that he called "Polytype" was in essence the same as the "Electro-Tint" process described by Charles

V. Walker in his 1855 book (12). In the USA Marion and Omri Behr learned about the electro-etching process originally patented in 1840 by Thomas Spencer, and they received a US patent in 1992 for their improved equipment, and registered the names 'ElectroEtch', and 'MicroTint' (13). The basic process itself has been shown to be in the public domain, as all the references to it, and its use by artists since 1840 have shown

For historical reasons, I prefer the original etymology, and the prefix galv-. So I use the name 'galv-etch' for applications in which the plate is etched, and for consistency, other names using the prefix 'galv-', like galv-on, galv-tone, galv-plate, or galv-type, which will be used throughout this booklet. The names therefore can be used freely, as can the 1850's name 'electro-etching'.

WHAT IS GALV-ETCH ?

In earlier editions I assumed too much basic knowledge of the scientific basis of electrolytic processes, which has led to very many questions, and a few printmakers making some mistakes that would have been avoidable had they understood the principles behind the galv-etch processes more clearly. Skip this section if you know all about electricity and electrolysis

For many centuries the traditional process used for etching a plate for printing was to use acid, either nitric, hydrochloric, and more recently ferric chloride, which is weaker but still relatively dangerous to use. Galv-etch is an electrolytic process, the principles of which have been known since the early 19th century (see a brief history of electrolytic methods), and the original process was described in 1855 and called electro-etching. It is similar to the process that takes place when a wet battery like a car battery is charged, and a reversal of the process that takes place when a battery is discharged. A battery produces a direct current, unlike the mains electrical supply, which is an alternating current. In order to charge a battery, a direct current must be used, and similarly, an electrolytic etching process requires a direct current, which is why the mains supply cannot be used until it has been 'rectified' and reduced in voltage from 230 or 110 volts to very much less, usually not above 12 volts. The equipment to do this is known as a transformer and rectifier and the most common household examples are the little power supplies that one can get for battery driven transistor radios and other electronic equipment. But these are not usually sufficiently powerful for electrolytic etching purposes, but another commonly used, off-the-shelf, transformer and rectifier that can be used is a car battery charger.

the electrolytic process

If two metal plates, say of copper, are placed parallel but not touching each other in a conducting solution of the same metal, say of copper sulphate, and they are connected to the terminals of a battery or of a source of direct current, then the current flows from one plate to the other through the solution. A complex process takes place in which the separate positive and negative 'ions' that make up the solution are separated and are attracted to the plate of the opposite polarity. Copper sulphate consists of copper ions and sulphate ions. Normally they are in equilibrium and they stick together like the positive and negative ends of two bar magnets. The current is actually able to flow because of the ions that give the solution the ability to conduct electricity. The positive copper ions are attracted to the negative copper plate (called the cathode) and the negative sulphate ions are attracted to the positive copper plate (called the anode). The copper ions stick to the cathode (if it is clean enough) and the sulphate ions are attracted to the bare areas of copper of the anode where they react with the copper of the surface, 'oxidising' it and therefore corroding it in the same way that an acid would. In fact at the point of contact, the process is exactly the same as being etched by an acid. It is as if an acid is being generated very temporarily right at the point of contact! While copper ions are becoming solid copper on the cathode, an equivalent amount of copper is being removed from the anode, and the copper sulphate is being kept in its original concentration, the copper removed from the anode, combining with the sulphate ions to form new copper sulphate at the same rate that it is losing copper ions at the cathode. There is a common fallacy that copper particles flow from one plate to another, but this is a misleading simplification.

electrical units and ohms law

It is important to understand something about the units in which electricity is measured. If all this is familiar then skip this section. The 'strength' of electricity is called the potential difference and is measured in Volts, and it is usually called the voltage. You can think of it like the pressure of water in a pipe due to the height of the water in a tank above a tap. The tap may be shut but the pressure is there all the same. The 'rate' at which the electricity is passing is the current and is measured in Amperes, and as the name 'current' implies, you can think of it as the rate of flow of water in a pipe only when the tap is opened. The 'power' of the electricity that flows is the potential difference (volts) multiplied by the current (amps), and is measured in Watts. The power or 'strength' of water flowing out of the tap depends on the pressure in the pipe and the rate it is allowed to flow by the tap. The quantity of electricity is the power multiplied by the time and is measured in Watt hours. Using the water analogy, when the tap is opened, a bucket can be filled at a certain rate, say a litre per minute, and the quantity is the total volume of water that has flowed into it after a given time.

When a current flows in an electrical circuit it meets a resistance measured in Ohms that reduces its rate of flow. In that it is like the tap, which increases its resistance as it is gradually shut, slowing down the rate of flow of the water. As an electrical resistance decreases, the potential difference, the voltage decreases and the current, the amperage, increases, and if the resistance increases, the voltage increases and the amperage decreases. The ratio between volts, amps and ohms is very simply expressed by Ohms Law. Ohms = Volts divided by Amps The inverse of resistance is the conductance G, which is important in helping to calculate the time required to etch a plate. G is calculated by dividing the Amperage by the Voltage.

The current flowing between copper plates in an electrolyte is related to the voltage of the power source and the resistance provided by the electrolyte. If the plates are very close together the electricity has little resistance to overcome to flow between the plates, and for a given voltage the amperage will be high. On the other hand, if the distance between the plates is greater or if the electrolyte is diluted and therefore offers a greater resistance (because the concentration of ions is lower in the solution), then the amperage will be lower. So a voltage of 4 volts meeting a resistance of 2 ohms will cause a current of 2 amps to flow. But 2 volts meeting a resistance of 0.5 ohms will demand a current of 4 amps (A = V/O). I hope that this simple explanation of principles and units will make the subsequent discussion of current, voltage, resistance simpler to understand and demystify the subject a little.

advantages of galv-etch over acids

1 The greatest advantage is that with the same equipment, plates can be either bitten down or built up to give a much richer variety of results, and that qualities of tone and texture can be produced that are not possible with other methods of etching and tinting. In addition, new plates can be created by 'electrotyping' from wax or other moulds or from relief created on silvered copper plates --the original meaning of the word galvanography.

2 Working with copper plates the chemical -copper sulphate -is absolutely safe to use, but gloves should be worn to protect the skin from drying and discolouring. With zinc plates the electrolyte -zinc sulphate -is much safer than acids, but must be used with care, avoiding contact with skin or eyes, and storing it safely out of reach of children.

3 For steel plates galv-etch is the safest method, although Bordeaux Etch with the addition of sodium chloride (common salt) can be used as a mordant (see section on Bordeaux Etch later). The electrolytes for steel -ferrous sulphate or ammonium ferrous sulphate -are classified as safe chemicals, but I find it prudent to wear gloves where there is any danger of skin contact.

4 The solutions are not weakened by use, in fact, the same solutions can be used for years and eventually pose no serious disposal problems (see section on safety precautions and Bordeaux Etch for method of disposal).

5 No gases or fumes are generated nor is there any precipitate or deposit formed in the bite, although a fine sludge from impurities can build up in the bottom of a tank, which needs occasionally to be filtered out.

6 The length of time taken for a given depth of bite on the same size and type of plate, under the same conditions of voltage and current, is always the same, and the biting can be controlled by time-switch, leaving one free to get on with other things.

7 Another advantage is that the backs of plates do not need protecting -the strength of the electrolytic action is proportional to the distance between the electrodes, so that only the edges and perhaps a narrow strip around the edge at the back need be varnished. The Galv-on semidry method leaves the backs of plates completely untouched.

8 The long-term cost is much lower as no very special expensive equipment is needed, especially with the galv-on semi-dry method, and the amount of electricity used is negligible -about as much as a light bulb. There is no danger from electric shock, because both voltage and current are low ( 0.5 to 8 volts at 0.5 to 10 amps).

9 The electrolytic action is not like the corrosive action produced by an acid, and so the range of varnishes, resists and grounds that are effective is much greater, because they must be simply electrically insulating and not acid resistant. Some heat-sensitive grounds require a low current and cool electrolyte, because galv-etch generates a little heat at the point where the etch acts.

10 The electrolytic action between the plate (anode) and the cathode is directional at right angles to the face, and so the edge of a resist is not significantly eroded or undercut.

11 The galv-on semi-dry method of etching simplifies the equipment required and allows one to work on only a portion of a large plate at a time, and can produce a great variety of textures, tones and images quickly with relative ease.

"Fleurs imaginaires, variations 1 -9"--a collage of printed squares, from 3 galvetched plates, combined in different orientations and colours. The plates were stopped with ethanol + shellac and an open bite was applied in several layers.

EQUIPMENT GUIDE -WHAT TO BUY

This guide assumes that someone using galv-etch for the first time will be making medium size prints -from plates up to about 40 cms on the longest side, and will be wanting to etch grounded needled, or tinted plates (see fractint later) or etch areas of open bite. Larger plates can obviously be made but to start off you may not want to invest a lot of money, and can make use of existing equipment like acid etching trays or photographic developing trays. In particular the galv-on semi-dry process (described later) can be done with the simplest equipment of all. Some readers may not be printmakers at all and will want to etch other objects like badges, name plates, dials, knife blades etc. I hope these pages will be helpful to them too, and I would only warn that if very small areas are to be etched, the current and voltage required must be low or the resists required must be very robust. Nearly all the equipment needed can be bought from DIY stores, electrical and electronic suppliers, motor spares suppliers or hardware shops.

Power supplies

The most important piece of equipment is a direct current power supply unit with switched voltage outputs and voltage and amperage displays. The most satisfactory and versatile type is a DC regulated laboratory power supply. In Europe, Velleman Instruments (website address: www.velleman.be) are distributors of a range of power supplies of this type. There are models which can be switched from 0 volts upward and with maximum outputs of 5, 10 and 20 amps costing from about 125 -300 Euros. To begin without spending a lot of money, you can use a 6 volt car and motorcycle battery charger, with built-in ammeter, and fused short circuit and overload protection. With a battery charger it is necessary to have a control box as shown and described on page 24, which can be made up by an electrician. The use of 6 volt batteries in motor cycles is becoming rare, but heavy duty 6/12/24 volt chargers can still be found capable of up to 20 amps. but voltages higher than 6 volts should never be used. For etching very small areas at low voltage, you can use a direct current mains adapter which can be switched down to 1.5 volts. Similarly, for small plates I have successfully used a small array of photovoltaic solar cells producing between 4 and 0.5 volts in bright sun. The control box for the last two options only needs a sensitive voltage and amperage display. There are other sources of direct current that can be used, like rechargeable batteries, but never use more than 6 volts, and then only with a control box to adjust and display the voltage by introducing a fixed and/or variable resistance. An accurate display of amperage is very useful also, which is used for calibrating the system to calculate the time required to etch (see times and tests).

Expanded diagram of standard all-purpose equipment for galv-etch -Key below.

[1] Deep plastic tray with appropriate electrolyte.

[2] "Backplate contact" -flat metal plate with metal strap soldered to back, varnished except face for contact with back of plate.

[3] Plate prepared for galv-etching, with area on back unvarnished to allow electrical contact on backplate contact.

[4] Grid to form cathode; heavy metal strips silver-soldered or mechanically fixed to frame, bent to allow grid to touch surface of electrolyte.

[5] Power supply -direct current, switched voltages, ammeter, overload cutout, and short circuit protection.

[6] Control box to use with any power supply without voltage switchable below 6 volts and without voltage output meter. Details of control box on page 24.

[7] Mains switched socket with time switch.

Two Laboratory power supplies from Velleman.

Left -switched 0 -18 volts and 5 amps (approx. 125 Euros).

A purpose made control box is not necessary with these power supplies.

Left -switched 0 -30 volts and up to 10 amps, with digital displays (approx. 220 Euros ) A larger model is available with output up to 20 amps.

12 amp 6/12 volt battery charger unit with switches and ammeter, and left -a purpose made control unit with halogen lamp, variable resistance, ammeter and voltmeter (details on page 23) to use with any direct current power supply other than ones shown above.

Robust type of battery charger for 6/12/24 volts capable of up to 20 amps. For large plates with open bite or for galvanoplasty, or galv-on, this option used with the control box may be required when large amperages are demanded. But never use 24 volts or 12 volts.

Power supply for galvetching small needled plates up to 300 sq. cms. -small DC mains adapter with a switched output of

1.5 volts and about 3 amps output at 1.5 volts. Shown next to control box, which can simply have voltage and amperage meters showing up to 3 volts and 3 amps.

Solar photovoltaic collector power supply, for small etched areas. For this and the mains adapter shown above the control box need not have a halogen lamp voltage reducer and the displays should be more sensitive and display only up to 3 volts and 3 amps.

Purpose made control box to use with 6/12 volt battery charger or battery -model with voltmeter and ammeter. Note ventilating metal grille over halogen lamp

Back of control box. In the centre at the back is the knob for the 50 watt 5 ohm variable resistor and on the right the switch for output either through resistors and ammeter or direct to crocodile clips.

chemicals and materials

Circuit diagram of control box above. Note that the voltmeter should be able to register the maximum output of the power supply when switched direct, and the ammeter in series only measures the current when the resistor and lamp are switched in The wiring should be heavy duty enough for the maximum amperage of the power supply.

For working with copper plates you will need copper sulphate (Cu SO4); for zinc plates: zinc sulphate (ZnSO4), and for steel plates: ferrous sulphate (FeSO4) or ammonium ferrous sulphate (NH4Fe(SO4)2). The chemicals can be obtained from suppliers of industrial chemicals. Pure copper sulphate crystals may be obtainable from gardening shops where it may be sold to make up Bordeaux mixture, used to spray plants against mildew. But do not use ready-made Bordeaux mixture that contains other ingredients. The amount of chemical will depend on the size of tray or tank you want to fill.

In general, the electrolyte solutions, all the cathode plates, plate contacts, grids, etc. should be of the same metal as the plates with which you are working, so in the section below I will use the word 'metal' to avoid repetition and confusion. So for example if you are working with copper plates, you will use copper sulphate, and the cathode plate or grid will be of copper, and any other metal like solder, bolts or pop rivets must be varnished. Similarly, if you are using zinc, substitute the word 'zinc' for 'metal'. Never mix metals or galv-etch one metal in the sulphate of another (see the section on ''chemistry of Bordeaux etch' for an explanation).

To begin you can use standard flat trays or vertical tanks used for traditional etching, provided they are deep enough. Later on when you become more ambitious and if you plan to do large areas of plating, or galvanoplasty, you may need a deeper vertical tank in which to hang plates. Photographic developing trays are quite suitable, and the type of tray used does not need to be acid resistant, but must not be metal even if enamelled or plastic coated.

For the galv-on semi-dry process (described later) you will need thick blotting paper and sheets of good quality felt 10 mm thick, 5 mm thick, and flat metal sheets and strips and self adhesive tape.

You will also need an assortment of strong electrical crocodile clips, heavy duty insulated wire and strips of copper, zinc or iron, depending on what metal you are using. For etching in flat trays you will need metal grids which are simple to make up out of wire and metal strips (illustrated later) or you can adapt off-the-shelf stainless steel grids by plating them with the appropriate metal. For etching in a vertical tank you can make up a metal cradle to hold the plate to be etched if you are using plates with backs already protected (described later).

preparation of the electrolyte

Add the sulphate to distilled or de-mineralised water until you have a saturated solution -when no more will dissolve. Approximately 250 grammes of copper sulphate or 500 grammes of zinc sulphate will dissolve in 1 litre of water, or 210 grammes of ammonium ferrous sulphate in 1 litre. The stronger the solution, the faster will be the rate of etch, but also the electrical resistance will be lower, so if you are galv-etching a large plate and find that your power supply is being overloaded, then you can dilute the electrolyte further to increase its resistance. If you then add 3 litres of water to the concentrated solution you will have a 1:4 solution. In the case of a 1:4 copper sulphate solution that means adding 62.5 grammes of copper sulphate to every litre of water.

plate contacts

The simplest way of making a contact for a plate to be etched, is to tape one or two thin flat metal strips to the back of the plate to be etched. Cut a piece of self-adhesive plastic sheet the size of the plate and put the flat strip against the back of the plate and then stick the plastic sheet over it. This way the back of the plate can be protected against being slightly etched. The flat strip can be bent up to sit clear of the electrolyte and the crocodile clip fixed to it. The strip also helps to lift the plate out of the solution and carry it around

Left -self adhesive plastic tape laid over back of plate to fix copper contact strips. Right -strip bent up to project out of electrolyte.

backplate contacts

Another method you can use for making a contact with a plate to be galv-etched in a flat deep tray is to solder or tape a flat metal strip to a small flat plate of the same metal to lie on the bottom of the tray, which makes a contact with a bare area in the middle of the back of the plate. I will call this a backplate contact from now on. The back of the backplate contact and its strap should be varnished or covered with plastic.

Copper backplate contact with copper strip bent up to project out of electrolyte -strip protected by strong varnish.

The back of the plate you are galv-etching need not be varnished, as the electrolytic etching action is strongest on the face directly opposite the cathode. Only the edges and perhaps a strip around the edges need to be protected. If you use plates with backs ready protected, in a flat tray, then you will have to use a cradle making contact with the bare edges of the plate as described later.

cathode grid

The method that I recommend for a flat deep tray is to use a grid for the cathode (-ve), made from wires or strips of metal soldered or mechanically fixed to a frame. The frame of the grid should be bent so that the wires of the grid are just immersed in the surface of the electrolyte. The spacing of the wires should be slightly less than the distance from the grid to the plate. A stainless steel off-the-shelf grid can be used for galv-etching, as it will be soon plated with the metal. But it must be completely degreased and the current turned on the moment it is immersed in the electrolyte or else it will begin to be etched by copper sulphate (see Bordeaux Etch).

If you use the equipment for plating or galvanoplasty (creating a new negative plate against a mould), or for depositing a dark tone onto an area, you will be removing a significant amount of metal from the grid (anode in that case), then you will need a plate suspended to touch the electrolyte. You can use the standard grid with a plate the right size fixed below it with plastic self adhesive tape.

Copper cathode grid in plastic etching tray 48 x 36 cm. 6 cm. deep,

flat tray for galv-etching line or tint

To start with, if you are galv-etching plates that have been grounded and needled, or fractinted, you can use a conventional flat etching tray. The tray needs to be quite deep, at least 6 cms. If you have not got a tray deep enough, you can use the kind of plastic food storage trays sold in supermarkets, because the galv-etch solutions are not corrosive, and don't need the special materials required for acids. Don't use metal trays though, even if enameled, in case of electrical short circuits.

In order to calculate the time required to galv-etch you will need to "calibrate" the setup you are using -a process which is more fully described in the section on 'times and tests'. For this you need a test plate with exactly 100 square centimeters of exposed metal.

vertical tank

The alternative to a deep tray is a tank in which plates can be hung vertically from a bar or over the edge of the tank.. Vertical tanks are increasingly used for etching and most of them can be adapted for galv-etch if they have sufficient depth to hang the plate and the cathode opposite and parallel with about 5 cm between them. Vertical tanks can be made for galv-etching from large polypropylene or other plastic 'jerry cans' or water storage containers with built -in taps as shown below. It is a good idea to have a tank with a tap a few centimeters above the bottom, in order occasionally to empty it without stirring up the deposit that eventually accumulates on the bottom. Using a vertical tank with sufficient depth is a much better way of doing galvanoplasty or plating, but can be used for all purposes if it will take your largest plate.

Vertical tank with tap, 35 x 35 x 15 cm holding 18 litres, with cradle and anode copper sheet for plating, made from a heavy duty plastic storage can with the top cut off and edges bent in. The large volume of electrolyte is not exhausted by galv-etching or plating, and does not pose a disposal problem.

supporting a plate in a vertical tank

If you wish to use a larger tank with the plate vertical, one way to suspend a plate and to provide a contact and protect the back is to cut a sheet of self-adhesive plastic sheet to the size of the plate and fix two thin strips of metal against the back of the plate. The strips can be bent over to hang over the edge of a vertical sided tank or to hang from a metal bar across the tank. Contact from the power supply can be made to the metal strips or to the end of the metal bar. If you are using plates with backs ready protected the plate can be held on a metal cradle hooked over the edge of the tank, made from a broad strip of the correct metal with the edge turned up on which to rest the plate with a bare area to make contact with an unvarnished area on the edge or back of the plate.. All the metal bars, straps, clips, rivets etc. must be well varnished against being etched, just leaving the points of electrical contact with the plate bare.

For the vertical tank make a cathode plate of the correct metal by soldering or taping thin metal straps to each end, to hang over the edge of the etching bath. Alternatively a square plate with a long single strap can be used, which can be lowered into the tank to control the resistance. The cathode strip or square should be able to hang opposite the centre of the plate and be parallel to it. If it is not, the galv-etch may not be even in depth. To stop them being etched and prolong their life, seal all the metal crocodile clips, backs of plates, bars, straps etc. with ethanol varnish, or a strong stop-out varnish, leaving bare only those areas to be in direct contact with the plate. A grid cathode can be used in a vertical tank as well, unless you are using it for plating or galvanoplasty.

Detail of print from deep etched zinc plate etched in vertical tank

BASIC PROCEDURE IN GALVETCHING

using a standard tray and grid system

Fill the tray with electrolyte to the height of the bottom of the grid and then remove the grid. Lower the plate to be etched into the electrolyte by its strip contacts. If you are using a backplate contact, put it into the tray with the strip bent up at the right position for the edge of the plate, then lower the plate into the solution onto the centre of the backplate contact. Place the grid onto the tray, with its wires just immersed in the electrolyte. At this stage make sure that the battery charger is switched off, either at the mains, or by a switch or timeswitch on its output.

Attach the positive (red) terminal of the battery charger to the plate contact strip or the backplate contact, and the negative (black) terminal to the grid or cathode. Check that you don't have any short circuits -leads, straps or crocodile clips touching. Then switch on for a moment, and watch the ammeter and voltmeter to check that the current and voltage are OK and note the readings. If the needle goes off the scale, or the digital display shows above 10 amps or 5 volts, switch off quickly, lower the voltage setting and try again.

At this stage you may be calibrating your system with a test calibration plate, in which case follow the procedure detailed in the section on times and tests. If you are etching a prepared plate, calculate the time you need from the voltmeter readings (see section on times and tests). Then set the time switch, if you have one, leave it to etch for the required time. It is a good a idea to keep a record of what you have done on every plate.

If the ammeter reading is very high because the exposed area of your plate is large, then the voltage should be lowered by switching it a lower setting, or the resistance increased by switching in the control box described on page 24, or by the other means described later (galvetching very large plates).

An uneven bite can be caused by the cathode grid or plate not being parallel to the plate and opposite its centre. There is a slight tendency for edges to bite more deeply than the centre, which can be counteracted by having the cathode grid slightly smaller than the plate if you notice a problem. Narrow open bite areas tend to bite more deeply than broad ones, something that can only be avoided by biting in short steps and stopping them out sooner. Similarly, isolated lines bite slightly more deeply than closely spaced hatching.

Typical tray based galv-etch equipment

[1] plastic tray

[2] copper backplate contact or plate to be etched with copper strip taped to back

[4] copper grid

[5] laboratory 10 amp power supply with regulated variable voltage and amperage, digital displays, overload and short circuit protection

[7] Electronic mains supply timeswitch and control with display.

open bite or galvanoplasty in a flat tray

A flat tray can be used for plating or open bite provided that you have some means of controlling the surge of current caused by the very low resistance of a plate with large areas of bare metal in the electrolyte. The control box shown in the diagram on page 24 can be inexpensively made up from off-the-shelf components. Note that adding a resistance like this in series, has the effect of reducing the voltage over the anode and cathode (see section on times and tests). For plating, a grid (which becomes the anode) is not ideal as it is etched away and a solid plate can be attached to the underside of the grid.

etching a plate in a vertical tank

A large tank requires a larger volume of electrolyte, but its greater width allows you to see the progress of the etch more easily and you can have more control over the distance between the plate and the cathode grid or plate. The cathode should be about the same area as the plate, and it should be hung directly opposite its centre. The tendency for lines or areas near the edges of a plate to be etched more deeply than the centre can be counteracted by making the cathode plate slightly smaller and therefore closer to the centre of the plate to be etched.

When plating or deep etching large areas of open bite with a strong current (amperage) there is often some loose deposit produced, and the advantage of a vertical tank is that it does not drop back onto the plate, but sinks to the bottom of the tank. This can then be emptied and filtered and the clean solution returned to the refilled tank. If you don't have a tank with a tap, use a plastic tube as a siphon, and start the siphon going by holding it all under the electrolyte surface (with gloved hands) until it is filled with liquid. Then close both ends and take one end out and put it into the receptacle to store the electrolyte. Don't start the siphon by sucking the liquid up it For storage I use plastic camping water storage jerry-cans, with taps.

deep etch and open bite

Large exposed areas of a plate will increase the current required from the power supply, so to keep the current within the limits of the power supply's ammeter, the resistance can be controlled by lowering the voltage output of the power supply with the controls that you have. This will increase the time taken to etch, but will decrease the intensity of the etch per unit area.

There is not usually any need to protect the whole of the backs of plates because very little electrolytic action will take place "round the corner" as it were. The ions in the solution are most strongly attracted to the nearest surfaces, which are the facing sides of the anode and cathode plates. This also makes it easier to make an electrical contact with the back of the plate, avoiding the need for crocodile clips and possible marks on the surface.

GALV-ON SEMI DRY METHOD

For certain purposes -for etching a small portion of a large plate; for applying a particular texture over an area without using fractint (see later) or aquatint or other alternatives -I have developed a method that does not require immersion of the plate in the electrolyte, and therefore does not need a tray, grid, or vertical tank with cradles etc. The method is best suited as an alternative to open bite, but it can be used to etch needled lines or tint, and is proving to be rich in new possibilities. I have called the new method “galv-on” as it expresses the way that it is done flat on a surface by forming a sandwich of felt and other absorbent materials soaked in electrolyte on top of the plate to be etched, backed by a cathode plate.

The area of the metal plate to be etched is prepared -masked with varnish or a stencil -then the plate laid face up on several sheets of blotting paper or newsprint on a flat level surface, with a thin strip of metal under the edge to attach to the positive terminal of the power supply. A thick pad of good quality well-washed felt is soaked in the electrolyte, allowed to drip dry for half a minute, and then placed over the whole area to be etched. A flat plate of the same metal as the plate is placed over the felt area, connected to the negative terminal.

Then place a block of wood or board on the cathode plate and weight it with something heavy until some of the electrolyte squeezes out of the edges of the felt. The amperage should not exceed about 10 amps, so if you are using a battery charger, it may be necessary to have an additional resistance as previously described switched in (page 23).

Preparing a plate pieces of blotting paper and felt laid over exposed areas of plate.

Turn on the current for slightly longer than you would need to etch in a tray or tank, but the precise time required will have to be calculated by experiment as described in the next section.

The current will pass through the electrolyte held in the felt and will etch a texture over the area that will depend on the quality and condition of the surface of the felt. The texture is usually more or less uneven but never uninteresting. To make the texture more even, several layers of thick blotting paper soaked in electrolyte can be placed between the surface of the plate and the felt, and trapped bubbles of air squeezed out with a roller. To reduce the unevenness still further, the felt/blotting paper can be moved a couple of times in between a series of short etches. Other porous materials can be placed next to the plate under the felt to produce different textures, like soft non-sized papers, fabrics etc. A paper with a strong printed image or with a design in a water resistant varnish, soaked in electrolyte, laid face down on the plate and backed with blotting paper will leave a ghostly negative image etched into the plate. I have experimented with etching through negative screened laser-printed photographs, soaked in electrolyte, and then placed face down on the plate cleaned with acetone, with interesting results. But this cannot be considered yet as a method for precise photomechanical reproduction, but the ghostly images etched will appeal to some printmakers.

The sandwich of plate, dry blotting paper, tissue papers, felt etc. backed by the thick layer of soaked felt and then, the copper cathode plate and board being laid down to receive the weight.

Detail of a print from a plate produced by the galv-on semi-dry method -layer on surface of plate: dry crumpled tissue paper, backed with layers of thick blotting paper and felt.

One way in which the galv-on method can be used is to create a ‘collage’ of various cut and torn papers, thin felt, fabrics and materials over a masked area, backed up with the thick soaked felt. The different porosities and textures will offer different resistances to the current and will etch to different depths to reproduce the collage in different tones and textures. If the elements of the collage are not wetted first in electrolyte, then they will buckle as the electrolyte soaks down into them with unpredictable but always very interesting effects. A mask or stencil made with a slightly porous material like thick cartridge paper, previously soaked in water (so that it does not buckle) will show as a lighter tone with a soft edge. If air bubbles are created by the wetting and buckling, they will not be etched at all.

needled lines or tint with galv-on

To etch lines needled in a ground, or a uniform aquatint or fractint use several sheets of good quality clean blotting paper well soaked in electrolyte under the felt layer. Divide the time required into 3 or 4 equal intervals and in between each, examine the progress and lift up and rotate or move the blotting paper and felt to even out the variations in strength of etch. Areas not etched at all are due to air bubbles that can be eliminated by using a small hard rubber roller on the back of each blotting paper layer. New felt must be very well washed in strong detergent to remove the natural oiliness in the wool.

After a while the top of the felt will collect metal that has not stuck to the cathode, which has to be washed out. Pieces of blotting paper can be reused if they are clean, but when they become too discoloured, discard them.

“Eclipse 7” – galv-on, 3 zinc plates 35 cm x 25 cm, proofed in 5 colours

TIMES AND TESTS

To appreciate the text of this section it is useful to understand the meaning of the electrical units used which are explained earlier (what is galv-etch : electrical units). The time required to etch to a given depth can be simply calculated if you have a means of measuring the amperage and voltage that the power supply is delivering when the plate is in place and the system is switched on. These are dependant on the resistance provided by the area of bared metal on the plate, the strength of the electrolyte, the distance between plate and grid and to a small extent, the temperature. But all these factors can be taken into account by 'calibrating' your setup by making a special plate about the size of the grid or cathode plate, with an area of bare metal measuring 100 square centimeters (15.5 square inches). This should be in the form of several rectangles distributed over the area of the plate. Protect the back with a self adhesive plastic sheet (holding the contact strip), place the plate in the electrolyte and switch on. Leave the current on for a minute to let the amperage and voltage settle down and note the readings on voltmeter and ammeter. If you have a regulated power supply, set the voltage at 1.0 and take an ammeter reading, then set it at 1.5 volts and note the amperage and so on up to about 3.0 volts. You can then calculate the resistance R of the system by dividing the voltage by the amperage. You may get slightly differing results for R at different voltages, but if they do not differ greatly, take the average and note it down for future reference.

calculating the time to etch

Then when you have a plate with lines drawn in a hard ground, prepared for etching, in the same tray or tank, with the same electrolyte and distance, you can calculate how long to give it to bite the lines very lightly or to bite them quite strongly. The table below gives a series of numbers F for copper, zinc and steel (iron) plates, which you multiply by the resistance R you obtained by calibration and then divide by the voltage that you are using (if you have a regulated power supply on which you can set the voltage). If your power supply is unregulated -a battery charger or rechargeable battery pack, then you must put the plate in and turn on for long enough to read the voltage (see discussion later in this section).

T = F x R/V ; where T = time in minutes; R = resistance obtained by calibration with 100 sq.cms., and V = volts; F is obtained from the table below :

Values of Needled lines (lightly Needled lines(heavily F for 1 ohm etched -0.2 mm) etched -0.5 mm) copper 20 60 -80 zinc 30 90 -110 iron 40 100 -120

Simply, the time taken to etch a plate depends on the voltage -the higher the voltage, the less time it will take and vice-versa. Each printmaker has his own preferences about the depth of bite required, so the values for F are a guide based on my own ideas of the meaning of 'lightly etched' etc. It is harder to give a method for calculating the time required for deep etch or open bite, as these are more subjective and depend on an individual's expressive intentions. Note that this method of calculation does not depend on the size of the plate but is valid for any plate size within limits (within the limits of a given tray/grid/electrolyte calibration test).

If you are wanting to etch a plate with open bite or any kinds of treatment that do not fall into the category of needled lines, make a test plate of the size you will most often use, with a typical range of the kinds of marks you use. Calculate the time for a light etch as above, halve it and then galv-etch it. Take it out, dry it and stop out a strip, and put it back for the same number of minutes, and so on in about 8 10 steps, noting exactly what you were doing. Then clean it and proof it, and keep it as a guide to the times to achieve the results you want. For very deep etch the times for each step should be doubled or tripled.

Note that very small test plates can give a very misleading idea of how larger plates will behave, because the current intensity could be so great that grounds will be lifted and the bite will be irregular and results discouraging. So trials on small plates must be at lower voltage and current than you need use for larger plates. Larger plates in a tray with large exposed area of open bite may overload a small power supply, and if that happens, there are a number of different options:

1. If you do not have a power supply in which you can regulate the voltage from 0 -5 volts, you can insert a resistance like a 12 volt halogen lamp and/or a ceramic resistance in series, that is, between one lead from the power supply and either the anode or the cathode. The voltage over the anode and cathode will drop and the time taken for the galv-etch will increase accordingly. A more sophisticated means of control is the type of box illustrated on page 23 with a variable resistance, halogen lamp fixed resistance and two-way switch, voltage and amperage meters.
2. You can dilute the electrolyte -this will increase the resistance and lower the voltage and amperage, and the etch will take longer, and be of a lower intensity. If you change the electrolyte concentration, then you will have to recalibrate it.
3. You can use a different power supply like a rechargeable battery or a power supply with switchable output voltage. If you use a battery it is essential to have a control box with voltage and amperage displays (see page 24).

the effect of voltage and amperage

There has been some discussion of the importance of only using low voltage and that the use of a low voltage was an original discovery in an article by Marion Behr in Printmaking Today (13 -“Electro-Etch III”). My research has shown that the earliest uses of Electro-Etching in the 1850’s involved the use of a low voltage (about 1 volt) because that was the practical limit of the Daniell’s or Smee’s cells that were used to supply the current. There is no doubt that a low voltage can be used, and there are a few circumstances where it is an advantage. But as can be seen from the tables below, the voltage output at the electrodes is not the same as the voltage set on an unregulated power supply like a battery charger, a battery or produced by a solar photovoltaic array, but is reduced when the resistance of the plate is low, and is reduced still further by the addition of a resistance in series. In fact it is not voltage that is important, but amperage that determines the quality of bite. The ratio of voltage to amperage is constant for a given resistance and reducing the voltage reduces the amperage proportionally. If the time calculated to deep etch a plate at low voltage is considered too long it can be increased, and the amperage intensity per unit area will increase proportionally, but the type of resist will need to be more robust.

The tables below are examples and a guide to voltage and amperage at various switch settings, using an unregulated power supply like a battery charger. The first table is for a small needled plate, and the second, a plate with a large area of open bite. These represent the extremes in normal practice.

Table of voltages and amperages for a needled copper plate 275 sq. cm. in 1:4 copper sulphate, with 6 cm between plate and grid.

Switch settings + 5 ohm resistance +12 volt bulb current direct to Electrodes

low 1.1 x 0.7 (amps) 2.4 x 1.6 4.2 x 2.4 6 volts

high 1.3 x 0.9 2.9 x 1.8 5.5 x 3.1

The use of a very low amperage and voltage is advisable only if one is using a fragile resist on a very small plate. After a little experience the voltage required to produce an acceptable amperage for a given plate size and treatment can be found and noted. For practical purposes most useful electrolytic action from a printmaker's point of view takes place in the range of about 5 amps down to 0.5 amp, and a creative printmaker must use the level that is appropriate to her/his work:

Table of voltages and amperages for a large copper plate with 625 sq. cm. (100 sq. inches.) of exposed metal in 1:4 copper sulphate, with 6 cm between

plate and grid. Switch settings + 5 ohm resistance +12 volt halog en current direct . low 0.5, 0.7 1.3, 1.8 3.8, 4.2 6 volts high 0.6, 0.9 1.6 , 2.2 4.5, 5.5

low (0.5 -2 amps) for special purposes: turpentine-based soft ground and other greasy fragile resists; medium (2 -5 amps) for most purposes: galv-tone, etching lines in hard ground, aquatint, ink ground or fractint; high (5 -10 amps) for deeply bitten sculptural or textural effects or to create relief, viscosity or embossing printing plates using very strong resists, or for galvanoplasty or plating.

It is always a good idea to start with a very short bite and take out the plate, rinse it and examine it carefully with a magnifying glass for pinholes or scratches which should show clear and bright in a dark ground. The galv-etch process is unforgiving about carelessly grounded or ill-treated plates. Stop any faults and then continue with the process. If a ground shows signs of breaking down, then lower the amperage by turning down the voltage, or increasing the resistance of the system.

A time-switch is a very useful accessory -There are a large variety of simple off-the-shelf mains electronic time-switches which can be quickly set to cut the power supply to the battery charger after the set time.

An electronic timer unit to control the mains electricity supply to the power supply unit (battery charger or other) with digital display and setting buttons on an extension lead.

galv-etching very large plates

If the size of plate overloads the power supply, the safest solution is to lower the voltage by switching to a lower setting or if you are using an unregulated supply like a battery charger, include a 12 volt, 50 watt halogen lamp in series in the circuit, or make up the control box described on page 24, and accept that the time taken will be much longer.

If the nature of your image allows you to work on smaller areas of a large plate at a time, then the galv-on semi-dry method will provide a simple solution without needing a heavy duty power supply.

If you are working with very large areas of open bite for relief or viscosity printing, and where you do not want the galv-etch to take a very long time by reducing the voltage and amperage considerably as previously described, you may have to have a very heavy duty power supply with a capacity of 20 ohms or more, with a very strong resist. If you have a large area of open bite on a medium size plate, then a tank can be used with the plate suspended on a cradle, and the current controlled by lowering the cathode, instead of reducing the voltage by means of a control box.

If your plate is very large overall, it is more practical to use a deep horizontal tray with a grid cathode. But the grid cathode frame must be made of metal heavy enough to prevent it from sagging in the middle, and joints should be mechanical rather than soldered -that is, passed through holes in the frame and bent to hold. The electrolyte may have to be further diluted to increase the resistance and keep the load on the supply within limits.

If your power supply will not cope with a large plate, a 6 volt lead-acid battery with heavy duty leads can be used with a more diluted electrolyte. If you cannot measure the voltage or the current flowing, there is a danger of having a current high enough to etch very rapidly and break up a ground after a short time, if the resistance offered by the plate/electrolyte/grid are low, so examine the plate frequently to check the depth of etch and for pinholes and signs of the resist breaking up. The battery may be flattened quite fast and if you cannot wait for it to be recharged, you may have to have 2 batteries being charged alternately.

If you intend to etch very large plates read the section on safety precautions first.

Proof from two deep etched plates, one intaglio and the other over printed in relief 40 x 40 cms

special effects

One of the features of the way galv-etch works is that it is sensitive to the surface it is biting -edges are bitten more quickly than flat planes, and irregularities like lines, texture, are enhanced, rather than etched out. So an area of open bite will be slightly deeper at the edges up against the stopout varnish or ground. Any lines in an area of open bite are retained, although broadened progressively. Any texture, even the grain of the metal, and any oxidized area, is enhanced to give a fine grained matte surface which prints as a very fine tone. Marion Behr has called this 'Microtint' (13), but I prefer to call it galv-tone, because it is more like a deep even plate tone. So the tones in any print can be subtly darkened, simply by stopping out and giving a very short galvetch. A plate open bitten in stages after progressive stopping out will show a gradation of tones, the edges of which will be clearly defined by a line -the change of level. The tone at any level can be darkened by reversing the terminals for a time, which will deposit metal back onto the developing texture and around the edges of any ground or varnish. This amplifies the crystalline effect of the bite and softens the hard lines around the areas of tone. The longer the time given to the reverse 'galv-plating' stage, the darker the tone, which will resemble the effect of 'carborundum'.

A deep galv-plated area can be burnished or scraped and treated like a mezzo-tint. But galv-etch cannot produce the deep blacks that are the attraction of real mezzotint.

Example of open bite producing graded galv-tone on a copper plate -at each stage the polarity was reversed to darken the tone.

Zinc alloy plates give a greater range of galv-tone than copper or steel. A series of overlapping areas of very shallow open bite will progressively darken the overlaps more noticeably than successively deeper layers. On copper, the galv-tone seems to be slightly darker if a very low voltage and current is used. The tone can be made even darker by allowing the electrolyte to dry and crystallize on the open bite area and leaving it to oxidize for a while before continuing with the open bite. After the first galv-tone, you can draw over the matte finish with wax crayon or lithographic pencil, which will resist further action and show up as lighter lines or shading.

The quickest and easiest way of producing a deep tone is to use the galv-on semi-dry method (page 25). The texture in the tonal area will depend on the absorbent material soaked in electrolyte that is in direct contact with the plate.

Don't try to galv-etch zinc plates or electrodes in copper sulphate, because zinc tends to precipitate copper ions from the solution and weaken it (see the chemistry of Bordeaux Etch).

"Brantome -Dronne" a print from a zinc plate produced with galv-tone over a needled outline 33 x 33 cms

galvanoplasty or galv-plating

If instead of biting into a needled grounded plate, you reverse the terminals and make your plate the cathode, metal will be deposited into the lines, and built up in relief. If the projection is very fine, no more than one would get with a drypoint burr, then the plate will print rather like a drypoint, only last longer because the projecting metal is less fragile than a burr. But more interesting to me than just reproducing the effect of a traditional method, is the completely original effect of applying an open bite over a plate with fine relief lines produced by the process described above. The results are unique to this process, and give a print with very subtle tones and grain, in which the raised lines act like a burr in the tonal areas, and if they are lightly burnished, print as very fine white lines, an effect quite unobtainable in traditional intaglio printing.

The voltage and current need to be low, and the lines very clean, so it is essential to thoroughly degrease the plate. A way to clean lines is to galv-etch the lines first very slightly, before reversing the terminals, which establishes an electrically 'clean' line in which to deposit metal. But if the line is deep, then the burr' will be doubled, building up on both edges of every line, a phenomenon that can be exploited for expressive effect.

Another way of using relief is in the way galvanoplasty was originally used, by creating a new plate by depositing copper over threedimensional modelled relief made with wax, glue, card, tissue paper, or any other means from which you couldn't normally print. The relief is then brushed with a liquid silicone wax and coated with graphite which provides an electrically conducting layer, and connected to the cathode (-ve) and 'plated' with copper. The current required is about 0.5 amps/100 sq.cms. or 0.03 amps/sq.inch -and the coat should be quite thick, at least 2 mm. which will take some hours to deposit. Then the new plate, which is the negative of the original relief, is backed with a filler of epoxy resin (often sold as 'liquid metal') to stop it being flattened in the press, and then is parted from it. It can be printed in relief, intaglio or a combination, using different viscosity inks (see section on proofing). If you want to reproduce the relief of the original plate rather as a positive, then you will have to make a mould of your original with wax, plaster of paris or similar moulding material, which can be coated with graphite before depositing the metal. Before making the mould, the original should be dusted with French chalk or any substitute (not containing asbestos) to aid separation. Then dust the graphite powder onto it with a brush. If it does not stick, try breathing on the mould to make it slightly humid and then the graphite should stick to most materials. If that does not work on some materials try a very thin coating of liquid silicone fu