Nontoxic Printmaking, Safe Painting & Printed Art

A Short History of Electro Etching              CONTENT  |  SEARCH    
and Photography

     AddThis Social Bookmark Button
Charles Negre - painting based on calotype photograph, appr. 1853 

©  Cedric Green FRSA,
revised  2012 and 2019

Electricity, Light and the Printed Image:

A Short History of the Origins of Photographic

and Electrolytic Methods in Printmaking

Image shows detail of Fleur Imaginaires (bottom left)   
plate galv-etched with open bite areas (bottom middle)
and electro etching equipment (middle panel)


Cedric Green was born in Africa,

and trained in a school of architecture where it was still

considered an art, closely linked to sculpture and painting.

During a period of 30 years he produced buildings

and exhibited drawings, designs, sculpture and paintings,

and also taught at the Cheltenham School of Art,

and Sheffield University in England. 

Then in the 80s

he became fascinated by printmaking

and after acquiring the basic technical skills, moved to France,

restored an old farmhouse in the hamlet of Bêlèterie

for home and studio and began working full-time in 1991,

painting and making experimental prints. 

Over a period of years he has carried out research into safer methods

of making prints and eliminating the toxic acids

and solvents traditionally used.

He has revived some 19th century electrolytic methods

for etching and making plates which he has called Galv-Etch,

and discovered a new electrochemical mordant

to use with zinc plates, called Bordeaux Etch.

He has documented this research in articles,

a booklet entitled Green Prints and in a website

containing most of the content of the booklet.

The following article was first published in El Grabado no toxico: Nuevos procedimientos y materiales, ISBN: 84-475-2810-3, University of Barcelona, Figueras Ferrer, Eva (Editora), in Chapter III. LA SOSTENIBILIDAD EN EL GRABADO, por Eva Figueras, Friedhard Kiekeben y Cedric Green.

Electricity, Light and the Printed Image:

A Short History of the Origins of Photographic

and Electrolytic Methods in Printmaking

The contemporary search for safer, non-toxic and environmentally acceptable processes has been largely provoked by the introduction of modern technology and chemicals, that had replaced safer processes and substances that were widely used in the nineteenth century, like egg albumen, gum arabic, gelatine, collodion, metal sulphates, electricity and sunlight. 

 The fascinating early history of the development of photography is bound up with the contemporary search for photomechanical printing methods, and closely paralleled the development of electrolytic processes for printing [3]. 

Photography and electrolytic processes were used, together in some of the best photomechanical methods developed during the nineteenth century [4]. 

This article describes the genesis of these methods with some technical explanation of how they worked, only some of which have had a contemporary revival. 

Some that produced superb results at the time will seem unacceptably complicated today; others described are ripe for exploitation now by resourceful printmakers.

The indisputable inventor of photography, Joseph Nicephore Niepce was, like many extraordinary men of that period, interested in a wide range of subjects, and he invented, among other things, the internal combustion engine with fuel injection, patented in 1807!

 He began his photographic researches in 1816 from a background in lithography. 

 He compensated for his lack of talent as a draughtsman by using a camera obscura and was obsessed with the idea of being able to fix the images he obtained in it.

Camera Obscura types, 1820  (above, below)

Joseph Niepce, The Bishop of Amboise, 1826
First successful attempt at 
photomechanical reproduction

Niepce - first photograph 1826 - 

view from his window - 

8 hour exposure

It was known at that time that various chemicals reacted to light and were hardened and made insoluble and so a suitable sensitized varnish would be hardened in the lightest areas [4]. 

This meant that if the unhardened varnish could be removed, baring the metal which could then be etched and printed in intaglio, he would have a means of simultaneously mirroring the camera obscura picture and producing a positive and permanent ink image [6]. 

Niepce had his first success in 1822 with bitumen of Judea mixed with oil of lavender, exposed for several hours under an engraving which was oiled to make it transparent. 

The areas not exposed to light could be washed away with turpentine and oil of lavender, and the dark areas etched in acid. 

In 1826 he produced a pewter printing plate of the Cardinal d'Amboise - the first successful attempt at photomechanical reproduction. 

In the same year, using his heliographic process, he produced a photograph from nature, a view from his window, which required an exposure of eight hours in a camera obscura.

The theatre designer Louis Jacques Mande Daguerre joined the race to find a way of producing a camera obscura image on an iodized silver coated copper plate. 
This had actually been suggested to him by Niepce in 1829. 

His breakthrough came in 1835 when he accidentally left an exposed plate in a closed cupboard in which a mercury thermometer had broken. It took him until 1837 to find out how to fix the image with salt, something that Henry Fox Talbot had discovered three years earlier. 

Niepce formed a partnership with Daguerre but died before they could publish their results [4]. His cousin Abel Niepce de St. Victor continued the partnership and invented albumen negatives. 

He continued work on trying to develop metal printing plates by the heliographic process.

Daguerrotype - 
original version and as restored              

At that time there was an acknowledged need for an easier way of producing high quality reproductions of works of art, original works or popular views to illustrate books, which up to then required the making of steel engravings, each of which could take up to a year to produce [3, 5]. 

Printed photographs were perceived as the solution and the competition was later stimulated by a prize of 2000 francs offered by the Duc de Luynes in 1856 for the best method of photomechanical printing and another prize for the best method for making permanent pigment-based photographic prints [3].

Fox Talbot - photograph on salted paper 

In parallel with the development of photography, the discovery of electrolysis was exciting much interest and experimentation. 

After the accidental discovery by Luigi Galvani in 1789 of Galvanism, or chemically produced electricity, Alessandro Volta built a galvanic battery formed by alternating zinc and copper plates separated by fabric soaked in an acidic solution [7]. 

In 1834 Michael Faraday postulated his Laws of Electrolysis and established the scientific basis of the ranking of different metals according to their electrode potential. Smee and Daniell invented improved versions of galvanic cells, using zinc and copper plates suspended in solutions of copper sulphates and acid separated by a permeable membrane. 

Mr. Thomas Spencer of Liverpool made the discovery that copper was deposited on the copper plate or negative metal and that the zinc plate was corroded or etched, for which he was granted a patent in 1840 [9].

Description of early arrangement for elecrolytic 'engraving’ 
 by Thomas Spencer, 1841

Simultaneously Professor Jacobi of St Petersburg claimed to have made the same discovery [10]. If the cathode was a three-dimensional object or mould in wax, plaster of paris, or metal, coated with plumbago (black lead) or graphite to conduct electricity, then the copper formed a solid negative mould over the object. 

The utility of this was immediately recognized and enthusiastically used to reproduce small seals and other objects by the process that became known as electrotyping or galvanoplasty [8]. 

Later the process was elaborated to produce much larger objects by applying a direct current from a galvanic cell to a separate cell containing a couple of metal plates in a metallic salt solution, which dissolved metal from the anode (+ve) and deposited metal on the cathode (-ve). 

The process of electrotyping become very widely used for creating printing plates, plating metal objects, gilding objects, decorating silverware and steel cutlery [9].

Charles V Walker - title page of 1855 book on Electro Etching 

Charles V Walker - title page of 1855 book on Electro Etching 

From then on there was a rapid development of electrolytic processes and in 1852, Charles V Walker was able to document and describe all the electrolytic processes that were currently known, in his book Electrotype Manipulation, in two parts, which went through 29 editions by 1859 and was also published in the USA [11]. 

Part II covered those processes which were of particular application in the Arts and included detailed descriptions of a process called Electro-Etching, patented in 1847, in which exactly the same equipment was used as for electrotype, but the poles were reversed and the plate on the positive pole prepared with a smoked wax ground through which lines were scratched. 

A single Daniell cell was used which provided a direct electric current of about one volt, and the exposed lines "submitted to the action of the nascent oxygen" were effectively etched. He considered this process of very great importance for artists, and it was subsequently widely used and included in every account of new methods for etchers. 

This process was also adapted by the steel industry for marking cutlery and other products and is still used today [16]. 

Charles Walker also described a novel and dangerous process of drawing directly on a plate connected to one pole of a series of batteries with an insulated stylus connected to the other - an electric arc burns an etched line which will print in intaglio [11].

Another process Charles Walker described at length was called Electro-tint or galvanography, which was attributed to Professor von Kobell:

"It consists in painting on white metal with etching ground or varnish:- the several shades are obtained by the relative thickness of the layers of varnish; the whole is then plumbagoed; and the deposite obtained on it is used as a plate to furnish prints. Prof von Kobell, after obtaining a plate, examines a proof; and if too faint, he makes a mould of the plate; and having obtained a deposite, which will be similar to the original painted plate, he puts varnish on the parts which give impressions too pale, and obtains a second deposite on this, which when removed will give prints of a better character..." [11]

By white metal he means a silvered copper plate and the deposite is an electrotype, from which an intaglio print could be made. The word galvanography was from then on loosely used as an alternative to electrotype for specifically graphic applications. The term Galvanography was also used to describe the Jacquemin process, in which a drawing was made on a plate with lithographic ink dissolved in albumen and water. It was then heated to coagulate the albumin and make the ink insoluble, and then the plate was electrolytically etched.

After the publication of the heliographic and daguerreotype techniques in 1839, there was frantic international competition to find ways of making permanent ink prints of photographs, partly stimulated by the prize offered by the Duc de Luynes. Many of the methods used electrolytic processes in one way or another, starting off with a daguerreotype, in which the image consisted of tiny dots of mercury amalgam over a silver substrate on copper plates.

The dots acted as a slight resist to certain mordants, which would attack the silver in between. The earliest attempts, by Alfred Donne in 1839, and Joseph Berres of Vienna in 1840, simply etched the daguerreotype directly from which only a limited number of good prints could be pulled. Berres used a solid silver plate for the daguerreotype which could be etched more deeply than a silver coated copper plate, and so got more prints.

Hippolyte Louis Fizeau - first attempt 1843 

Hippolyte Louis Fizeau developed probably the most successful method, patenting it in 1843 [13]. He boiled the daguerreotype in potassium hydroxide to strengthen the resist dots, lightly etched it in nitric acid and then wiped it with heavy linseed oil, as if for printing in intaglio. 

Then he electroplated it with gold, which was deposited only on the highlights not protected by oil. 

He removed the oil and etched it again to deepen the dark areas, and finally electroplated the whole plate with copper to strengthen it so that many prints could be pulled [4]. 

The plates required some hand retouching, and the results were impressive despite difficulties in achieving good half-tones, 

but the method was so complicated and expensive that it never caught on.

Hippolyte Louis Fizeau - 
1840's "Excursions Daguerriennes"                

One of the most talented early experimenters, was the painter and photographer Charles Negre who took up the methods originated by Niepce and his cousin, and elaborated them by introducing an electrolytic step, plating the partly developed steel plate with gold to protect the half tones, then aquatinting it and etching it in nitric acid. 

He received a French patent in 1856 and was a finalist in the Duc de Luynes competition [6].

Charles Negre - 1860's - competition test plate                

Meanwhile Fox Talbot had been experimenting with methods of fixing what he called photogenic images on paper and only later joined the race to make printing plates. 

He patented a process called photoglyphy in 1858, which used gelatine sensitized with potassium dichromate on a copper plate, aquatinted with gum copal powder melted onto the plate, and then etched in ferric chloride [6]. 

This process was later elaborated by Karl Klic of Vienna in 1879 and is now known as photogravure or heliogravure, which eventually became the most successful and widely used photo-engraving method until the introduction of new chemicals and photo-resists in the 20th century. 

It was the noxious nature of these processes which stimulated a return to old gelatine-based methods in the 1980s and a revival of heliogravure.

Fox Talbot - photoglyphic engraving 1858

Fox Talbot - photoglyphic engraving 1858

    Stieglitz, photogravure, 1894

But the Austrian, Paul Pretsch took a completely different approach and patented a process called photo-galvanography in 1854 [15]. He discovered, while he was manager of the Imperial Government Printing Office in Vienna, that gum arabic sensitized with potassium dichromate, silver nitrate and potassium iodide on a glass plate, sensitized under a photographic negative to sunlight, had a tendency to swell and reticulate when washed in water. 

The depth and intensity of the worm-like texture that was produced was proportional to the exposure and gave the grain required for half-tones. 

He then created a mould of the reticulated gelatine with gutta percha, which was a widely used gum from a Malayan tree. He then deposited copper by galvanoplasty onto the mould, which duplicated the original reticulated gelatine. To print it in intaglio, he had to make a second electrotype of his matrix. 

He filed another patent in 1855 describing refinements to his process, using gelatine instead of gum, hardening it with tannin and applying the process to making relief prints. 

He formed a company in London to produce a series of albums of commercially printed photographs called 'Photographic Art Treasures' in 1856 and employed Roger Fenton as his photographer and manager [14].

Paul Pretsch - 'Photographic Art Treasures' - Title page 1856

Sadly his venture was not a commercial success. The process of production of each plate took about six weeks, and he was dogged by lawsuits from Fox Talbot who claimed that his Photoglyphic patents covered Pretsch's inventions. 

In the end he proved the originality of his work but the company folded in 1858. He was awarded medals for his half-tone photo-galvanographic plates at the Great Exhibition of 1862, and was a finalist in the Duc de Luynes competition 1867. 

He did a great deal of work illustrating the Journal of the British Museum, but found it difficult to get on in London, and returned to Vienna a disappointed man, and died of cholera in 1873.

Pretsch - illustration in Photographic Art Treasures           

Alphonse Poitevin, aware of the pioneering work of Pretsch on the reticulation of gelatine, filed a number of patents in 1855 for a very similar process, substituting a plaster of Paris mould for the gutta percha. 

But he turned his attention to the behaviour of dichromated albumen exposed to light on a lithographic stone, and it is with this method that he won the prize for photomechanical printing offered by the Duc de Luynes in 1867. 

He is also credited with being the originator of the technique of collotype, which uses the carefully controlled reticulation of exposed and heated gelatine on a glass plate, which is then printed like a lithograph. 

Green Prints : Electrolytic galv-etch

Ricci/Otto - Collotype 1890’s

Collotypes were capable of reproducing photographs with exceptional detail and subtle silky half-tones, and the technique was perfected by Otto Albert in Berlin in the 1870s [4].

Although it was not an electrolytic technique, the method patented by Walter B Woodbury in 1866 is of very great interest here, because it was licensed for use in France by the firm of Goupil & Cie, publishers of Fine Art reproductions. 

They set up a factory at Asnieres to produce photographie photoglyptique or Woodburytypes. It was not strictly a printing process, but a method of reproducing the three-dimensional image of a gelatine print in which the depth of tone was given by the thickness of coloured gelatine. 

The original produced by a purely photographic process on a metal plate, was cold pressed into a lead mould, which was then used to impress hot coloured gelatine onto paper [3].

Goupil & cie - Woodburytype factory  

The reason Goupil's use of this process is interesting here is because they later started producing reproductions of photographs by a different process from copper plates, but kept the precise process a closely guarded secret [6]. 

The results were exceptionally good, with rich velvety blacks and subtle half tones, although a lot of handwork is evident on the plates, a process which earned the name of Goupillage. 

The author of this article has examined some of their plates, conserved in the Musee Goupil in Bordeaux, and believes that they were produced by an electrolytic process related to Paul Pretsch's photo-galvanography in which they used the Woodburytype press to make a lead mould of a reticulated or grained gelatine original, on which an electrotype could be easily deposited and separated [20].

Goupil & Cie - catalogue 1878 


As early as 1840 Thomas Spencer described a method which was later used extensively for making large copper plates for printing Ordnance Survey maps. Lines were drawn through a thick ground with a special tool, and then copper was deposited slowly into the cleaned lines, producing a linear relief plate [9]. 

This method was widely used for other printing purposes besides maps, including the illustrations of Spencer's original description. Electro-etching, introduced and recommended for use in the arts, gradually became much more widely used in industry for decorating and making metal objects. 

The steel industry in particular took it up for applying trademarks to cast and wrought iron pieces, and until recently, when laser methods emerged, was the standard method of marking stainless steel cutlery [17].

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 electro-etching became well enough known for artists who were interested to learn about it.

Commercial Electrotyping workshop

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 and its advantages regarding safety [23]. 

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 [24]. 

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 [25]. 

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 [23, 26, 27].

There has also been a revival of the original 19th century Heliography and photogravure processes using gelatine or albumen and potassium dichromate, and the best-known publicist of these processes invented by Fox Talbot, is Keith Howard [29]. 

He has also adapted methods used in the electronics industry for etching circuit boards using thin photosensitive film applied to metal plates, and refined them for use by printmakers as a safer alternative to the photosensitive chemicals previously available.

                                                                          Equipment for Galv Etch, Cedric Green

I began research in 1989 into non-toxic printmaking methods and from my base in Sheffield [UK], a traditional centre for electrolytic plating and industrial marking, I became aware of the long history of electro-etching. For my own use I found simple, safe and low cost methods using off-the-shelf equipment for the revived electrolytic methods. 

I developed an electrochemical method for etching zinc and steel plates using copper sulphate which I called Bordeaux Etch, and non-toxic methods for applying resists to plates and graining them using oil based lithographic ink called Fractint [26, 27].

In 1995 I began a campaign to publicise methods like Electro Etching, and to resist efforts to make printmakers pay royalties for using them. I created a website ( fully describing my low cost methods for etching electrolytically which I called Galv-Etch, and supplied free information on all my methods.

In 1998 Nik Semenoff and L W Bader published a paper in Leonardo on an improved mordant for etching aluminium and zinc which was similar to Bordeaux Etch [28]. 

Galv-On method - preparing a plate with collaged paper resists - Cedric Green    

The subsequent development of both electrolytic and photographic plate making processes has been very rapid and has been given a great deal of stimulus by the search for so called non-toxic methods, or methods which greatly reduce the dangers to health and the environment that were notorious features of traditional processes using acids, solvents, and photosensitive chemicals.

This paper was given at the 'Jornadas de Grabado no tóxico' organised by the University of Barcelona, and the illustrated Spanish version of it is available on this website. It forms part of the book in Spanish in which most of the content of Green Prints has been translated into Spanish and published by the University of Barcelona. Click here for details of this book "El Grabado no tóxico", which includes chapters by Eva Figueras Ferrer, Friedhard Kiekeben, Keith Howard, Juan Carlos Ramos, and Rosa Vives., 

©        Cedric Green  |  Last altered on June 9, 2012                   

back to top

R e f e r e n c e s: (click)


Selected Prints by Cedric Green

Cedric Green "Forgeron" example of Galv On technique (top)

Cite Englouti (2) (left)

deep galv-etched plate proofed

intaglio and over printed

Atlantide III    (right)

‘Atlantis 3”, part of a series illustrating

the book ‘A Modern Atlantis’


by the author

The alternative methods described in the preceding pages are in one sense traditional, in that they can be used to make conventional printing plates from copper, zinc and steel, using methods and materials that have been around for more than a century. In showing for how long electrolytic plate-making processes have been used, and how modern, inexpensive, everyday equipment and materials can easily eliminate what is clearly the most noxious etching process, I have tried to demystify and simplify galv-etch to make it as accessible as possible, and to communicate the results of my experience and research as freely as possible. 

(rigth)  Zinc plate 33cm sq. grounded, lines etched in Bordeaux etch, 
fractinted and stopped in 6 stages and etched as above.

The electrochemical method of using copper sulphate to etch zinc plates (Bordeaux Etch) was not documented for use by etchers before Semenoff, Bader and I researched it independently, but the chemical process involved is obvious and I would be surprised if it was not known and used during the 19th century.

I have found from the feedback that I get on the internet, that interest in electrolytic processes extends to many other crafts that use metals, and I have tried to extend my research and experience to describe ways of using galvanoplasty for instance. 

The use of the linked methods of ink-ground and fractint, salt tint and sugar lift tint, have the same effect, of using economical, quick, and simple means and safe materials to remove the barriers and inhibitions to creativity that the traditional"cuisine" has imposed. 

I hope that the new possibilities that the combined techniques offer will stimulate, even perhaps galvanize, other artists into creative discoveries that go way beyond those I've described. Even if the additional possibilities offered by ink grounds are not taken up, galv-etch can be used with traditional grounds and aquatint, or with a few other substitutes to produce a safer working environment.

Once the process of making and experimenting with plates has become simplified, clean, safe, agreeable, and can be done in a normal studio environment without special ventilation, masks, goggles, or anxiety, then imagination is liberated at the point where it is most important in printmaking, in the creation of the matrix.

Cedric Green: self portrait


Cedric Green's References:

1 Encyclopedie Hachette Multimedia, Livres Hachette, Paris, 1999;

2 Aaron Scharf, Art and Photography, Penguin Books, London, 1968, 1974

3. Pierre-Lin Renie, Le temps cisele, in Etat des Lieux, Musee Goupil, Bordeaux, 1994.

4 Raymond Lecuyer, Histoire de la Photographie, Paris, 1945

5 Francis Haskell, The Painful Birth of the Art Book, Thames and Hudson, London, 1987.

6. William Crawford, The Keepers of Light - A History and working guide to early photographic processes, Morgan & Morgan, New York 1979

7 Encyclopoedie Larousse Illustre, Paris, 1999.

8 G. Barclay, The First Steps in Electrotype 2nd. edition, G. Barclay, Soho, London, 1841.

9 British Patent No. 8656 ... AD 1840, Engraving Metals by means of Voltaic Electricity granted to Thomas Spencer and John Wilson.

10 Mr Thomas Spencer, An account of some experiments made for the purpose of ascertaining how far Voltaic Electricity may be usefully applied to the purpose of working in metal, Annals of Electricity, Magnetism and Chemistry, Vol.4 Jan 1840.

(See also by the same author in Westminster Review, Vol 34, II, 1840 pp 434 - 460)

11 Charles V WALKER, Electrotype Manipulation, Part II. Containing The Theory, and Plain Instructions in the Arts of Electro-Plating, Electro-Gilding, and Electro-Etching; with an account of the Mode of Depositing Metallic Oxides, and of the Several Applications of Electrotype in the Arts. Nineteenth Edition, George Knight and Sons, London, 1855.

Charles Vincent Walker, Electrotype Manipulation, Vols 1 & 2, H.C. Baird, Philadelphia, 1852.

12 Chattock R S, Practical Notes on Etching, 3rd Edition, Sampson Low, Marston, Searle, & Rivington, London 1886. (Electro-Etching for artists is described in full)

13 Hippolyte Louis Fizeau, British patent No. 9957, 1843.

14 John Hannavy, Roger Fenton, David Godine, Boston, 1976. (The process of photo-galvanography is described in detail)

15 Paul Pretsch, Improvements in producing copper and other plates for printing, British Patent No.2373, 1854.

16 Seymour Hayden, Etching for Copper Plate Printing, The Printing Times and Lithographer, Vol 8 (1882) Oct 15 pp.247 - 248. (Electro-etching and galvanography are covered briefly)

17 Electrolytic marking is done in Sheffield by: John H. Elliot (Monostamp) Ltd. and Eyre & Baxter (Stampcraft) Ltd.; In the USA by The LectroEtch Company, who have been doing it since 1947, (email

18 Charles V Walker Electrotype Manipulation, Part I. being the Theory, and Plain Instructions in the Art of Working in Metals, by Precipitating them from their Solutions, through the Agency of Galvanic or Voltaic Electricity 29th Edition, George Knight and Sons, London. 1859.

19 Maj.Gen. J Waterhouse, Paul Pretsch and photo-galvanography, Penrose Pictorial Annual 1910-11 Vol 16, Lund Humphries & Co, London. (see also Maj.Gen. J Waterhouse, Mordants for Zinc, The Photographic News, June 30 1882 for a description of etching zinc by galvanism)

20 Otto Lilien, History of Industrial Gravure Printing up to 1920, Lund Humphries, London 1972.

21 Pierre-Lin Renie, Goupil & Cie a l'ere industrielle - la photographie appliquee a la reproduction des oeuvres d'art, in etat des Lieux, Musee Goupil, Bordeaux, 1994.

22 S W Hayter, About Prints, Oxford University Press 1962.

23 N. Semenoff and C.Christos, Using Dry Copier Toners in Intaglio and Electro-Etching of Metal Plates, Leonardo, Vol 24, No. 4, pp. 389-394, (published 1991, received 1989).

24 Peter Jones, Spanish Printmaking Summer School, Printmaking Today, Vol 2, No 3 Autumn 1993).

25 Marion Behr, ElectroEtch I, ElectroEtch II, ElectroEtch III, Printmaking Today, Vol. 3, No 1, 1994, Vol 4, No.4, 1995, Vol 7, No.4 1998

26 Cedric Green, Intaglio without Tears, Printmaking Today, Vol 7 No.1, Spring, 1998.

and Galvanography Revisited, Printmaking Today, Vol 8 No.1, Spring, 1999. Galv-etching without Electricity, Printmaking Today, Vol 11 No.2, Summer, 2002.

27 Cedric Green, Green Prints, Ecotech Design, Sheffield, 2002

28 Nik Semenoff and L W Bader, Intaglio Etching of Aluminium and Zinc Using an Improved Mordant, Leonardo, Vol 31, No 2, pp. 133 - 138, 1998.

29 Keith Howard, Non Toxic Intaglio Printmaking, Printmaking Resources, 1998.




(first published 1995, with recent additions)

dangers of etching zinc plates with ferric chloride

Zinc plates are now very widely used by printmakers who are not concerned with trying to make huge editions, or who deep-etch plates for viscosity printing or embossing effects. Zinc is very much less expensive than copper and can be bought from building materials suppliers in large sheets, and are easy to polish. Students learning printmaking use zinc plates a great deal, and they can be bought ready polished and backed with a resistant coating.

It is now widely accepted that etching zinc with nitric acid is extremely dangerous, but many printmakers believe that using ferric chloride is a completely safe acid chemical to use because it has been used in the printed circuit industry for many years. This is only partly true for copper plates, where the products of the chemical process are a deposit of cupric chloride and a solution of ferrous chloride. But ferric chloride is a strongly acidic chemical and gloves, vapour mask and good ventilation are required.

But etching zinc plates in ferric chloride is a different matter altogether, and the process gives off bubbles of hydrogen gas which is explosive in air, produces a deposit of iron, which forms a crust over the etched surfaces, and the spent solution contains zinc chloride which is more toxic and corrosive than ferric chloride. The bubbles of hydrogen require removal with a feather to prevent an uneven bite and the iron crust is abrasive and the process of removing it damages the edges of the needled ground or a sensitive aquatint. When a deep bite is required over large areas of exposed metal, the chemical reaction heats the solution and gives off an extremely corrosive vapour of hydrochloric acid, carried up by the hydrogen. As any experienced printmaker knows, having to brush away bubbles and the deposit means bending over the etching tray, exposed to the vapours or gas given off, and wearing goggles, and vapour mask is uncomfortable and inhibiting. Vertical tanks are unusable in these conditions. As the solution becomes weaker ferric hydroxide is deposited and darkens it, and zinc displaces ferric ions in the solution forming the iron crust which becomes harder and harder to remove and the solution then is a mixture of unused ferric chloride and zinc chloride, which is more corrosive than the original and is very difficult to render safe for disposal.

A recent development which alleviates a litle of the unpleasantness of ferric chloride is Edinburgh Etch developed by Friedhard Kiekeben, which involves adding citric acid which speeds up the bite, and dissolves some of the sediment. But the mixture is still a strong acid, and my personal preference is to avoid the use of all acids.

etching zinc plates safely with copper sulphate

There is a much safer way of etching zinc, and also steel plates, that is electrochemical rather than electrolytic, and will satisfy those who want a single solution which is inexpensive and easily obtainable. That is to use a pure concentrated solution of copper sulphate. For etching mild steel plates (iron - not stainless steel) I have found that adding an equal quantity of sodium chloride (common salt) solution is more effective than pure copper sulphate, which has a tendency to 'plate' the steel and stop the etch. This mixture of salt and copper sulphate will also etch aluminium with the addition of sodium bisulphate - a weak acid - as has been shown by Nik Semenoff (16). I prefer to keep the mixture as simple as possible and avoid the addition of any acid. I have found that the salt/copper sulphate mixture works equally well with zinc, and may have a longer life and other slight advantages.

I have called this Bordeaux Etch, because a copper sulphate solution is better known to vine growers, farmers and gardeners as Bordeaux mixture (Bouillie Bordelaise), very widely used as a spray against mildew. The solution is very much safer to handle than ferric chloride, and a zinc plate can be etched without the production of any bubbles of gas, although gloves should be worn to avoid skin contact. An insoluble powdery deposit of copper is produced which is very easy to remove by brushing with a feather or a soft brush in a flat tray. The other advantage is that the initially blue solution remains quite transparent, and turns gradually colourless as it is exhausted, and the progress of the etch can be very easily seen in a tray by the formation of the deposit. Nik Semenoff and L W Bader described a mordant for zinc and aluminium, similar in some respect to Bordeaux etch in an article in 'Leonardo' which was published in Spring 1998 

To make up a solution follow the instructions given for mixing a concentrated solution of Copper Sulphate in the pages on preparation. I recommend a concentrated solution, but some research done at the Rietveld Academy in Holland by Ad Stijnman and collaborators has found that a more diluted solution will work. Do not use readymixed commercial Bordeaux mixtures supplied by gardening shops as it is often mixed with other chemicals, and sometimes contains no copper sulphate at all !.

the chemistry of bordeaux etch

The effect of Bordeaux Etch with zinc is essentially an electrochemical process and the results are very similar to galv-etch. Briefly, zinc has a much higher electrode potential ( Zn2+ = -0.76) than copper ( Cu2+ = +0.34), and as a result it displaces copper ions from the copper sulphate solution (CuSO4), and the zinc ions combine with the sulphate (SO4) ions to form zinc sulphate (ZnSO4). If the copper deposit remains in contact with the zinc there could be a side reaction - the metals in contact in a slightly acidic copper sulphate solution form a short-circuited galvanic cell called a zinc-copper couple - producing a very small quantity of hydrogen and thus making the solution less acidic (more alkaline). As the alkalinity builds up so that the pH goes above 7 there will be a reaction with the zinc and copper ions to give an additional precipitate of zinc and copper hydroxide. This side reaction can be exploited to create a texture over areas of open bite. But normally it is a good idea to brush away the deposit as it is formed which results in a more even bite and prolongs the life of the solution. There is usually a fine layer of black hydroxide adhering to the etched open areas which can be washed off, or comes off with the first proofs. Then the etched areas have a fine crystalline texture, similar to galv-tone, which helps to hold ink.

dangers of using salt in etching solutions

Some sites and books have recently suggested adding salt to copper sulphate to create 'Saline sulphate etch' , which may then be used electrolytically in the Galv-On process, or by mistake used to etch copper. But there are dangers in using salt or sodium chloride in solution, either added to copper sulphate or by itself. Using brine as an electrolyte generates chlorine gas, hydrogen gas, and produces caustic soda. Different toxic chemicals are produced when etching metals like zinc, aluminium, and steel. Free copper deposit produced by etching zinc plates in saline sulphate etch forms a 'zinc copper couple' which generates a current and produces chlorine, hydrogen and caustic soda. Free chlorine and hydrogen gas in a confined space like a covered etching tray can form an explosive mixture. If the chlorine gas is not channelled and collected, but mixes freely with the caustic soda, then sodium chlorate is produced . Sodium chlorate is a very toxic chemical banned since 2008 in the European Union where it was used as a powerful weed killer.

disposal of bordeaux etch

Disposal can be done in two ways : filter and save the completely spent solution to use as the electrolyte for galv-etching zinc plates. If you are not doing that, or have too much, then the solution must not be put down the drain because of the zinc sulphate and the residual copper sulphate left in it. To make it safe for disposal, you can add sodium carbonate (washing soda) or sodium hydroxide to it to neutralize it, until the pH value goes up to between 7.0 and 8.0, testing it with indicator paper. Copper and zinc hydroxide will be deposited as a sludge. Allow the sludge to settle, pour off the liquid, further dilute it and then it can be poured down the drain. Collect the sludge in plastic bags and dispose of it as required by your local authority. When neutralizing it, be careful not to allow it to become too alkaline because the hydroxides will be redissolved. If you are galv-etching copper plates as well as using Bordeaux etch, then keep the dilute copper sulphate used for that completely separate from the concentrated Bordeaux etch solution, in well marked containers. It is not dangerous to use the wrong one, but a diluted copper sulphate prepared for galv-etch will not etch zinc satisfactorily, and a partly spent Bordeaux etch solution, used electrolytically for galv-etching a copper plate, will deposit zinc on your cathode.