Spongotype: making a plate by electrotyping a monoprint

Yesterday evening I ran a workshop at the Regional Print Centre on monoprinting as serendipity, would have it, as part of my PhD. research into electro-etching I had come across this series of lectures given by Hubert von Herkomer. In one of the lectures he describes the process of making an electrotype copy of a monoprint plate. The illustrated examples are very striking and look more like drawings than etched plates.

Excerpt From: Hubert von Herkomer. “Etching and Mezzotint Engraving: Lectures Delivered at Oxford (1892).”

“You take a polished copper plate, and cover it with printer’s ink—cover it completely with the dabber, as if there were something to print Now, with brushes, hard and soft, and with rags, or your finger, or all combined, you wipe out the forms you require from the black ground. You will soon find that you can get the most delicate tones; the most artistic manipulation with your brushes is possible, and brilliant high light can be got out with a bit of wood pointed at the end. Here is a toy for a painter,—for it is painting pure and simple, the only difference being that the lights are taken away and the blacks are left. When your painting on the plate is done you put it through the press like an ordinary engraving; nearly all the ink will come off the plate, and you will find on the paper a splendid proof of your work. I know no method of drawing in pencil or colour that can approach the beauty of these printed blacks. The artistic mystery that can be given, the finesse, the depth of tone and the variety of texture, make this manner an almost intoxicating delight to the painter.

The Spongotype

Now it seemed a pity that such rapid artistic work should be limited to one print only, and I started with my assistant, Mr. H. T. Cox, to invent a method for multiplying impressions from the work done on the plate, and he completed the invention.

I have patented the process, merely in order to prevent anyone else from securing a monopoly of its use, but give it freely for all to use and improve upon.

Mix in equal parts graphite with German printing black and oil, and cover the copper plate with this by means of a lithographic roller. Then do your wiping away of the forms as before described.

Take equal parts of bath-stone scraped to powder, bronze powder, and asphaltum (also in powder): soak the two first in turpentine, and when quite dry mix them with the asphaltum, and place the whole in a little bag of fine muslin.

When your drawing is done, dust it over with this mixture through the bag, until the plate is covered. Then brush it off very carefully and gently with a soft camel-hair brush, and you will see your work again, but filled in different degrees with the powder Let this dry for three days, and then send it to an ordinary electrotyper, and tell him to deposit copper upon that surface, but with the strict injunction not to touch the face of the work; for the plate is perfectly ready for him to commence his depositing, the plate having been made into a proper matrix.

When you receive the deposited copper, which will be of the thickness of an ordinary plate for etching or engraving, you will see the reverse of what you did. You lowered the lights by wiping away the ink, and left the ink standing up for the blacks. Here you will see the lights high and the tones lower, in a sort of granulated surface.

This process, which is eminently suited for original work, opens up endless possibilities to the painter, who, in using it,

is hampered with none of the technical difficulties of an engraving process. He can get his result without having in any way departed from the mitier with which he is naturally familiar. And it is conceivable that by working on the electro-typed plate with dry-point and scraper results may be arrived at which will surpass in artistic quality anything that can be obtained by methods of reproduction hitherto practised.”


Demythologising electro- etch

“If two plates of copper be connected with the opposite ends of a voltaic battery, in a vesessel containing very dilute sulphuric acid, the plate connected with the copper of the battery will be attacked by the anion oxygen which is released during the decomposition of the acid”.

“By alternately exposing the plates to the action of the decomposing fluid and stopping out parts of the work, the required gradation in tints is obtained.”

Battery 1850

Battery 1850

“Electro-etching has the advantage of being free from the exhalation of any deleterious gas, but the apparatus required involving a battery and an extra copper plate, is more cumbrous, and the process itself more complicated, and does not appear to have been adopted for artistic work to any considerable extent.”

Chattock, R. S. (1883) Practical Notes on Etching. (2nd. edition) London: Sampson Low, Marston, Seale, & Rivington.

Although; the equipment we now have at our disposal is more effective, efficient and certainly can’t be described as cumbrous; the myth of complexity still sticks to electro-etching. Colin Gale and Megan Fishpool offer a key to demythologise the process in their excellent book ‘The Printmakers Bible’. They describe electro-etching as being “A reasonably complicated process and there are very few printmaking workshops with the equipment and ability to host it”. We are currently exploring the possibility of providing the equipment, training, and support fro electro-etching at The Regional Print Centre in Wrexham. If we can make this happen, it will help other artists to explore the mark making potential of electro-etch.


Electrotype Manipulation 1852

Describing electro-etching in 1852 “If, for instance, plates of copper be covered on any part of their surface with a stratum of varnish, that part will be excluded from the line of action, while all else is being consumed. Advantage has been taken of this, by coating the plate with proper composition and then tracing through it any design, of which an etching is required. The plate in this condition is submitted to the action of nascent oxygen, and the surface is readily and effectively etched. There is some superiority to  possessed by this method, over the ordinary etching by the use of nitric acid; for the operation can be conducted with considerable regularity; it can be rendered a slow or speedy process; and the results can be taken out from time to time, to be examined, and can be re-submitted in a moment.”

Face plate to Electrotype Manipulation

Face plate 1852


Proposal For Research Into Electro-Etch

Rationale For Proposed Research

Intaglio Etching remains popular today with artists who enjoy the creativity of its line, tonal range and gravitas of expression. Though its roots are in the fifteenth century it has adapted to modern mark making techniques such as photography and digital media, Smith, A. (2004 p.9). Many of the great artist have of the past and present have made intaglio prints as a significant part of their output – to name a few; Goya, Hogarth, Blake, Picasso, Chagall, Motherwell, Hockney, Oldenburg, Hodgkin.

For the last one hundred and fifty years nitric acid has been used as a mordant to bite etching plates. Today the traditional acid based printmaking studio is considered to be a hazardous work environment. The fumes from nitric acid are toxic, impacting on both individual health and environmental safety. The toxic nature of the chemicals, solvents and acids used in traditional printmaking require fume cupboards and specialist ventilation equipment that is beyond the reach of most artists.

Since the early 1990s a growing awareness of the potential health and environmental hazards of traditional etching techniques has led to a real interest in exploring safer and less toxic methods of etching and printmaking (Adam, R and Robertson C. 2007). Another response has been that a number of colleges and art schools have taken etching out of their curricula. (Keith Howard 1993 p. 20) suggests that the lack of exposure to etching as an art form during secondary education and the potential health and environmental hazards of traditional etching will alienate potential students from the art form. He argues that the vitality of etching depends on young people being offered the opportunity to learn about and practice the art.


The teaching of etching in educational institutions is in decline due to:

  • The increasing cost of materials,
  • The cost of adapting the environment due to changing health and safety legislation,
  • The lack of an effective alternative to acid etching.

Research work and tasks carried out

The researcher is a member of the Regional Print Centre in Wrexham and has a close working relationship with the Leinster Print Centre in the Republic of Ireland. The initial research question came from conversations with members and staff of the two centres while he was researching the saline sulphate as a safe mordant of as part of his M.A. research.

“Are there etching techniques that can be used safely by artist’s in their homes, studios and places of education?”

There were three strands to the research process,

  1. Action Research: To form a reflective framework to bring together and examine the data and results of the scientific enquiry and practice as research.
  2. Scientific Experimental Enquiry: to identify and test techniques that can be used in artist’s home studios and places of education.
  3. Practice as Research: making artwork to explore the mark making potential of the methods identified by the experimental enquiry.

Same Metal Electro-Etching

Through the literature search a process known as electro-etch was identified as being the best replacement for acid as a mordant. Although electro-etching has been known about since the early days of research into electricity and electric cells (batteries) its use, as an artistic tool has been little exploited.

Electro-etching is based on electrolysis and provides a simple, safe and inexpensive way of etching metal. It can be used on copper, zinc, iron/mild steel. It can also etch aluminium that is significantly cheaper than the traditional metals used for etching. Electro-etching requires two metal plates – the one to be etched and another plate called the cathode; a battery and a plastic container holding a liquid, an “electrolyte”.

showing cellThe plates are placed in the electrolyte and each plate is connected to one of the terminals of the battery. An electric current flows from one plate to the other through the electrolyte and metal is corroded or etched from the plate. In same metal etching the anode and the cathode are of the same metal and the electrolyte is made up from the salt of that metal i.e. when etching copper both electrodes are copper and the electrolyte will be copper sulphate, when etching zinc the electrodes are zinc and the electrolyte is zinc sulphate.

When comparing same metal electro-etching to acid etch in 1883 Richard S. Chattock noted, “Electro-etching has the advantage of being free from the exhalation of any deleterious gas.”

The advantages for same metal electrolysis have been identified as

  • No toxic gasses are produced; this eliminates the need for expensive ventilation systems.
  • The system is self-sustaining so the electrolyte only requires topping up because of evaporation.
  • The stability of the system means that biting times can estimate accurately unlike acid, ferric chloride, saline sulphate or Bordeaux etch which tire over time requiring etch times to be adjusted for an ever weakening mordant.
  • Produces a better-drawn line than other mordants.

The problems that relate to the disposal of toxic chemicals are almost eliminated, because as long as the electrolyte is filtered occasionally, it will have an infinite life, Semenoff (1998).

Taking Keith Howards (1993) point that the vitality of etching is reliant on giving young people the opportunity to learn the art. From the literature and the research carried out so far it is clear that same metal and same metal salt etching is safe, effective, economical and can be used in a classroom situation.

Research Plan for next year

These objectives are based on the researchers learning from the previous research and were identified in a critical review of literature and research so far.

The overall aim is to explore and further develop the potential of electro-etching and electrolysis as an artistic medium.

The project objectives:

Build a community of practice:

  • It is envisaged that the centre will develop into a community of practice for electro-etching with members sharing information, experiences and learning together.
  • Easy to access electro-etching units, along with workshops for members, technical support and studio time at the Regional Print Centre in Wrexham should facilitate this.
  • This provision has the potential to provide a showcase and focus for the development of electro-etching in the U.K.

Collect analyse, interpret into lay language the currently dispersed literature on electro-etching and electrotype:

  • As identified in the literature review there is a need to gather together the dispersed scientific and technical information on electrolysis and put it into a form and language that will make it understandable and useful for artists. There is a clear need to demystify the electrolytic process and make it accessible. The purpose is to provide a comprehensive source of information for electro-etching.

Continue research into the electro etching of aluminium:

Produce a portfolio of work that explores the unique mark making potential of electro-etch, focusing particularly on the etching of aluminium.

  • The researcher intends to develop a portfolio of work over the next twelve months that explores the techniques and the mark making potential of electro-etching and electrotyping.

Continue research into the art, practice and science of electro etching and electrotyping.


Chattock,R.S. (1883) Practical Notes On Etching, 2nd. Ed, London: Sampson, Low, Marston, Searle & Rivington.

Howard, Keith. (1993). ‘Safe Etching and Photo Etching: The next generation’. Print Making Today, Vol. 2 No 3. pp. 19-21

Semenoff, N and Christos, C. (1991) Using Dry Copier Toners and Electro-Etching on Intaglio Plates Leonardo, Vol. 24, No. 4 (1991), pp. 389-394.

Smith, A. (2004) Etching: a guide to traditional etching techniques, Ramsbury, Marlborough Wiltshire: The Crowood Press.

Self Etching Battery – Passive Galv-Etch

This etching process was first described by Cedric green on his website and by Alphonso Crugera in his recently published Handbook. In this process the cell becomes a self etching battery.

disimilar metal corrosion

Using a flat tray

Using a flat tray


When two metals with different potentials are placed together in electrical contact in an electrolyte, one metal will act as anode and the other as cathode. The electro potential between the metals is the driving force for the corrosion of the anode. Zinc has a potential of -0.762v on the index and copper +0.340v giving a difference of 0.422v. The anode becomes vulnerable when the difference is over 0.15v. Making the copper zinc coupling ideal for etching. This form of corrosion is also known as dissimilar metal or sacrificial anode corrosion. In a corrosive environment the metal with the lowest electrical potential (the zinc) becomes the anode in the cell and sacrifices itself for the more “noble” metal (the copper).

Zinc passive etch. Plate first inked in intaglio and secondly as a relief plate.

Zinc passive etch. Plate first inked in intaglio and secondly as a relief plate.

Passive etch. Inked as a collagraph plate.

Passive etch. Inked as a collagraph plate.

etching 2

The etch on the plates is very deep and is great for viscosity inking.


Experiments in the electro etching of aluminium.

salt bridge and aluminium

Each of the cells is a 1.5 L flask. The electrolyte in the anode cell is copper sulphate 25g made up to 1L with tap water. The cathode is copper mesh in an electrolyte of sodium chloride 25g made up to 1L with tap water.

The salt bridge is made up of 50ml water 5g potassium nitrate and 1g-agar agar.

potassium nitrate salt bridgeThe aluminium anode measures 65 x 250mm divided into 8 sections each section was etched for fifteen minutes.

Etched at 7.5v. 0.04amps. Using two salt bridges of 50ml.

plate one

At the start of etching there were some static bubbles in the mesh. These were shaken free and a small drop of washing up liquid was added as a wetting agent, the bubbles did not re-appear.

Showing no bubbles at cathodeThe resulting etch is fine with a good tooth for holding ink. At the fifteen-minute intervals the newly exposed areas of the plate were degreased, it was also necessary to brush away copper deposits from the previously exposed areas of the plate. Etching was active for over two hours and the electrolyte was still active when etching was stopped. Very small fast moving bubbles were visible on the anode but there were none visible on the cathode.

There was no smell of bleach or chlorines coming from the set up. The Ph at the anode remained at 4 from start to finish. The Ph at the cathode started at 6 climbed to 7 at finish. Alumina gel appeared in the cathode cell after half an hour. This can be controlled by the use of sodium gluconate.


Prior to using the salt bridge a test plate was etched in each of the electrolytes, the plates were pitted rather than etched. Etching with the bridge produced a good tooth that holds ink.

Why is there no gas visible on the cathode?

Etching will take place with electrolytes made up of 50-50 sodium chloride, copper sulphate as low as 5g to a litre of water. Clearly this saline sulphate mix will etch aluminium without electrolysis but the resulting etch is pitting rather than etching. With electrolysis a nice tooth produced that holds ink really well. The staying power of this electrolyte has yet to be tested. The salt bridges also build a very high level of resistance into the system. It’ll be interesting to see what the reaction of it will be to an increase in the volume of electrolyte and increase in plate size. Without the resistance created by the salt bridges it will be possible to reduce the voltage and increase amperage and possibly further reduce the copper sulphate and sodium chloride used in the electrolyte. Given the scale this system is working at there is probably no danger from chlorine gas or other nasties like caustic soda.

But, because of the concerns about this Bob Perkin suggested that sodium carbonate might be used replace the sodium chloride solution. A quick and dirty experiment was run using sodium carbonate and the results are encouraging. The system was set up as above (fig. 1) with sodium carbonate in the cathode cell.  As with the sodium chloride there were no bubbles visible at the cathode.


There will certainly be no danger from chlorine in this set up but there could well be another genie in the bottle. Although this does not qualify as a non-toxic approach it is a little less toxic and slightly safer and easier to control than saline sulphate? Whether the mark making potential, length of working life or quality of etching is as good as or better than saline sulphate will take a little more experimentation.