Using a Safer Mordant Intaglio Etching
on Aluminum and Zinc
Nik Semenoff, (Artist-in-Residence)
Department of Art and Art History
Dr. L.W. Bader, (retired)
Department of Chemistry
The authors describe an etching bath containing copper sulfate, table salt and a weak acid for use on aluminum or zinc plates. The bath in use has a pH reading of 2.5 - 4.5 and will not harm skin or clothing, as it does not contain strong acids. During etching, the copper sulfate is removed, leaving common chemicals that can be disposed of down the drain quite safely in many areas. The bath can be recycled quite easily so that copper compounds can be reused instead of being disposed.
Etching of intaglio images on metal has been practiced since the seventeenth century, being produced mainly on copper and later on less expensive zinc. Today, with artists printing smaller editions, zinc has become quite common, as it is readily available from suppliers for use in making photo-mechanical engravings for newspapers and other relief printing processes. It is not considered as good a material as copper, but the high cost of polished copper makes zinc an acceptable alternative. While etching can be done on other metals and alloys, these are not used by the average printmaker. Since etching of metal usually calls for the use of acids or other corrosive solutions, the handling and disposal of spent mordant has become more of a problem in this environmentally concerned society.
While research in electro-etching (Semenoff & Christos, 1991) is being carried on by some printers, the more common use of corrosive etching solutions has prevented that technique from becoming popular. Printers and artists are not familiar with electronics, and therefore continue to use methods known to them. A simple, environmentally safe, inexpensive, and readily available mordant would be helpful for today's etchers. With the high cost of artists' materials, even the price of zinc has become too much of a financial burden for many students. Since editions at art schools are usually limited to six to twelve prints, a search was undertaken for materials that react much like traditional metals, yet withstand the printing of smaller editions.
Use of Aluminum in Place of Zinc
Aluminum, an inexpensive material already in use by some artists, would easily stand the printing of small editions as required by schools. If unblemished common-grade metal could be purchased from local metal suppliers, the saving could be even greater. The large sheets could be sheared to appropriate sizes, and since both sides of the metal can be used, the price of aluminum is reduced to about 1/20th that of zinc plates. To protect the back of the metal for later use, the sheet is covered with Mac-Tac, a self-adhesive vinyl commonly used as kitchen shelving material. All that may be required is extra polishing of small scratches that appear on some mishandled sheets.
It is generally accepted that aluminum and magnesium are less desirable metals for the process because they are soft and also produce a coarser grained image than copper. This may be of concern for some artists because of the images they choose to create, but for many artists these softer metals are not a problem. For artists who prefer to make large prints, but in small editions, the problems with aluminum become less of a consideration. Certainly for students who have a limited material budget, aluminum will serve their purpose. At this University, the metal was purchased in both 12 and 16 gauge, but it was found that the thinner was more than adequate. Because of the reduced cost of aluminum plates, the size of intaglio prints has greatly increased since this process has been introduced.
Techniques Possible with Aluminum
While engraving and dry point are both practiced on aluminum, the softer nature of the metal limits the edition. Although the electro-facing with harder metal is possible, the authors doubt if the cost would warrant the use of the cheaper aluminum in the first place. For the small editions required in this Department, the direct intaglio techniques such as dry point have not been overlooked, and are used in conjunction with etching and aquatinting.
Hard ground, soft ground and aquatinting are the most commonly practiced techniques and commercial grade aluminum has been more than adequate for these techniques. Aquatints are processed as with zinc, with the results on aluminum being indistinguishable from the harder metal. Large editions, although smaller than that possible in copper, could still be impressive. One senior student has pulled an edition of 25 with no noticeable deterioration of the plate, indicating that a larger edition is possible.
Mordants for Aluminum
A number of chemicals will corrode aluminum, but are either expensive or not readily available to the printer. The suggested chemicals have been stannous or ferric chlorides, both having been successfully used by printers. One of the problems found with both chemicals was local availability and a fairly high cost. Attempts to order stannous chloride from a supplier in the USA were hindered by the fact it could not be exported by common carrier without an expensive surcharge for the handling of hazardous materials. Experience with ferric chloride made it less desirable because of the red cast that forms around the etching area. Also, the need to etch the plate upside down in this chemical was a concern. While electro-etching was possible, the need for numerous power supplies to accommodate the many students simultaneously working in the etching area made the technique too costly.
Use of Copper Salts in Mordant
Semenoff's experience with printmaking processes, and his interest in chemistry began the research for a better etching bath. His observation that acidified copper sulfate would erode aluminum was the basis for the mordant. The first experiments with copper sulfate were to combine it with hydrochloric acid (which was purchased as technical grade muriatic acid), commonly used in cleaning fresh concrete, or for controlling the pH of swimming pools. The copper sulfate was purchased from a local garden supply outlet (where it is sometimes labeled bluestone) and sold for controlling algae growth in dugouts.
Since both of these chemicals need not be reagent grade, the less expensive, more readily available materials are quite adequate for this purpose. It was found that this mordant would etch both aluminum and zinc, though not as fast acting on zinc. There was no need to use separate trays, as chemical action was not affected, as is the case of nitric acid and the use of zinc and copper in the same bath.
As the etching action takes place, a deposit of very fine copper is formed at the opened surface. Very fine bubbles of hydrogen are also formed, which remove the copper created by the electro-chemical exchange with the aluminum. This keeps the process ongoing as the copper is flushed by the gas from the thin lines and fine dots. A soft brush or feather may be used to remove the copper sludge and speed the action slightly, although it was found that most students simply leave the plate for a specified time. In time, the reaction will slow down as the acid content is reduced and a clear gel-like substance of aluminum hydroxide is formed. Increasing the acid will not completely refresh the solution as the copper is depleted and the action eventually stops. By adding more copper sulfate, the action will continue, as long as the other chemicals are present is sufficient quantity.
Use of Common Salt in the Mordant
To find a safer and less expensive source of chlorine, Semenoff decided to try common table salt, which is pure sodium chloride. Most salt sold as table salt is labeled "iodized" and contains small amounts of sodium iodide. This makes no difference to its use in this technique, but non-iodized or coarse salt is much cheaper. Since it is available in bulk quantity for use in most water softeners, it is the most practical way to purchase the chemical. It is available in fine granulation or as rock salt; use of the fine grade is preferable as it dissolves easier to make up a bath. Although a simple solution of copper sulfate and sodium chloride worked, it was found that an acidified solution would perform much better. This would prevent the formation of the gel-like aluminum hydroxide and consequent reduction of etching.
As each batch of mordant became exhausted, different formulations were mixed for the studio and tried by the students. In the early experiments, hydrochloric acid was used as the acidifier, but since it entered into reaction with the aluminum, it would become depleted, and the aluminum hydroxide gel would form in the etching bath. By choosing sulfuric acid, which prevented the formation of aluminum hydroxide, we prolonged the use of the mordant. Since sulfuric acid does not react extensively with aluminum in this technique, it is not depleted during the life of the bath and the solution remains acidified. It will be neutralized by the aluminium hydroxide produced, and slowly raises the pH reading of the bath. It was decided to find a dry compound that would be safer to handle than liquid acids and would replace the sulfuric acid, which tuned out to be very successful.
There are, on the market, a number of products that produce a weak form of sulfuric acids when combined with water. They all contain sodium bisulfate (sodium hydrogen sulfate) as the major ingredient, and in many cases the only chemical, usually found in an impure form. The most common form is sold as a toilet bowl cleaning agent (Sani Flush ) which contains deodorizers and other materials to meet market demands. Another source is a vehicle radiator-flushing compound that is available at automotive supply houses. It may come as a two-part package, but only the bulkier powder containing sodium hydrogen sulfate is needed. The third source is from jewelry craft stores that sell goldsmithing supplies. Sold under a number of labels, sodium bisulfate is the main or only ingredient. This chemical is used as a pickling solution to remove fluxes and oxides after hard soldering silver and gold articles, as it forms a weak sulfuric acid when mixed with water. It should be noted that sodium bisulfate, sodium hydrogen sulfate and sodium acid sulfate are one and the same compound. It should be listed on the container under one of these names.
Formula for a Dry Powder for Storage
By using only dry materials, the chemicals can be premixed and conveniently stored in its powder form. This reduces the chance of accidental spillage and uses less storage space. The dry powder may absorb humidity in the air because of the salt, resulting in the blue copper sulfate changing to green copper chloride. When added to water, the blue color returns. Since a number of various proportions worked, the exact ratio of each chemical does not seem to be critical. It was found that the quantity of copper sulfate was the most important chemical in controlling the reaction and establishing the amount of metal displaced. The amount of aluminum that can be removed is about eight to ten percent of the copper sulfate available. This is the ratio of actual copper molecules as compared to the hydrogen, sulfur and oxygen in the compound. The other chemicals were in sufficient quantity to carry on the reaction until all the copper sulfate was depleted. It is important that excessive copper sulfate not be added to the solution as a violent reaction on the plate would likely be the result. As the normal etching action decreases, the addition of copper sulfate alone will bring the bath back to life. Increasing the sodium bisulfate will increase the amount of hydrogen gas produced to some extent, which calls for constant brushing of the plate surface to prevent broken lines.
The etching time is comparable to the use of traditional mordants, with total etching being completed within 10-30 minutes, or less in the case of light aquatints. One important factor is the fairly constant etching action over the life of the etching bath as long as there was sufficient copper sulfate in the solution. Only when most of the copper was depleted, did the action slow down. By observing the intensity of blue coloring in the bath, the strength of the solution can be estimated. With such an indicator, students were less likely to over-etch their plates.
The formula that used in the Department at present is as follows:
CuSO4 (copper sulfate -- bluestone) 1 kilogram
NaCl (sodium chloride -- table salt) 250 grams
NaHSO4 (sodium bisulfate -- Sani Flush ) 25 grams
H20 (water) - depending on bath strength 10-20 liters
The powder is mixed by volume after an approximate weight is established for the chemicals. This is premixed dry in a five-gallon plastic container and stored until needed. It is advised that an appropriate mask is worn while mixing the dry copper sulfate and sodium bisulfate, if they come in fine powder form. When the salt in the mixture takes on humidity, there is less risk in handling the powder mordant.
Water is added to a tray to make up the working solution. Then the dry chemical mixture is added to bring it up to strength, using a rough calculation for the copper content or by judging the blue color of the etch. You should conduct tests to find the initial strength of the solution you like.
We have also experimented with the use of saturated solution of copper sulfate, which was kept on hand to be added to the depleted solution to see what might be the total life of the bath. It was found that the bath could be extended considerably, but the eventual build-up of aluminum salts was a limiting factor. On first mixing the bath, it would test about 1.0 pH; but on using the bath for only a very short time, the solution would stabilize anywhere between 2.5 - 3.5 pH, or higher. It is still an effective mordant at pH levels of 4.0 and above. This relatively weak acid solution makes it a very safe mordant to use in the classroom setting.
Advantages to Copper Sulfate/Sodium Chloride Mordant
Acids are extremely dangerous chemicals to handle, especially in a classroom situation. Since most art students are not concerned with technical matters (over the creation of the image), they tend to be lax in their handling of materials in a proper manner. While health and safety has become more important in the classroom, the elimination of as many dangerous materials as possible seems a step in the right direction. Since none of the above chemicals are considered to be dangerous to handle, there is now less concern about the safety of the student. Spills on skin or clothing are of only minor importance, as the weak chemical will not stain or do harm if removed quickly.
An important improvement in how metal is etched occurs with open bites. To obtain a solid black area, it is customary to apply aquatinting. Due to the particular electrochemical etching action of this bath, the surface becomes corroded in a rough fashion that holds ink very well. If the metal is homogeneous and does not have a longitudinal grain as a result of production, the mid-range tints can be achieved by stopping out the open bite when the proper tint is produced. Unfortunately, the common grade of aluminum we are currently purchasing has a pronounced grain in one direction, which is revealed in lighter than solid color tints.
Some students have had concern in creating the deep etches needed for viscosity printing, but this needs only the addition of copper sulfate to keep the bath alive. A higher concentration of salt and bisulfate may be needed to supply the chlorine and acid molecules for the metal exchange. In viscosity printing, a very large amount of metal is removed, especially on the larger plates now being used by our students. If there is a problem of the bath being depleted too quickly from the large amount of metal removed, the only cure is to make sure that the bath starts with sufficient copper sulfate. Constant monitoring may be needed in extreme cases.
If the bath was mixed with too much copper sulfate, a very violent reaction will take place. This produces a great amount of heat, which can destroy the hard ground resist. It may also lead to some of the fine metallic copper being bonded to the now coarse grain of the aluminum. Rubbing only forces the copper deeper into the rough metal and it can then take on a burnished state. To remove this unwanted copper, use a dilute solution of nitric acid, which will attack it, but leaves the aluminium alone
Recycling the Spent Bath
In the last couple of years, we have started to recycle the spent bath rather than throwing it away. It is placed in plastic containers and left to stand for a month or more. The other chemicals in the bath start to react on the copper sludge at the bottom and soon the blue color returns. In the place of the dark metallic copper on the bottom, a whitish powder appears. If one wanted faster exchange of the copper, I would suggest periodic stirring of the solution until the reaction is completed. The clear blue solution is drawn off and put back into service. It is less corrosive in some ways and preferred by many students. Salt and acid content seem to be sufficient and only copper sulfate is added as needed to keep the bath alive. This procedure has greatly reduced the amount of copper sulfate we require in the etching studio. It has be been found that the whitish sludge is made of copper compounds that can be reclaimed also by adding sulfuric acid solution or a fair amount of the sodium bisulfate material. If your solution is not recycling, try adding more sodium bisulfate to act on the copper particles.
Disposal of Spent Etching Bath
The properly prepared spent bath can be safely put down the drain with sufficient amounts of water, as all the chemicals can be accommodated by the drainage system. Table salt and sodium bisulfate are chemicals commonly put into waste disposal, and even traces of copper is already present within plumbing systems. As all of the copper sulfate will be reduced to a fine metallic copper at the bottom of the tray, it should be separated for disposal as a solid waste. For any remaining copper sulfate left in the spent etching bath, the solution is poured into a large plastic container and discarded aluminium plates are used to reduce the remaining copper. Aluminium, the only remaining metal, is present in common household alum, and disposed down the drain. If need be, the aluminium hydroxide could be precipitated from the solution by making it alkaline with the addition of household lye, borax, or washing soda. The sludge that is formed may be disposed as a solid in traditional ways. If zinc has been etched, then it is advisable to use commercial disposal services rather than using the drain system. It is recommended that you check with the Environmental Control Officer in your area for restrictions.
Concerns with the Use of Copper Compounds
It has come to my attention that some environmentally concerned groups are rejecting this process as it uses copper compounds. In areas where grapes are grown, the abuse of copper sulfate over the centuries, has contaminated the ground water, lakes and streams. Over the years, tons of copper sulfate has been put into the environment, leading to stricter use of this chemical. If one takes the trouble to reduce all the copper sulfate with scrap aluminium, zero amount of copper will be put down the drain. This process is no more dangerous than other mordants now used if care is taken in handling the materials. When dealing with health boards and concerned groups, make sure they understand the alternative methods now used and that all the copper can be removed from the solution. If there is any doubt, the spent bath can be sent to special disposal facilities, like one would with used copper etched in nitric acid baths. It should be noted that in the use of copper plates and nitric acid, there would be copper nitrate produced that is now escaping into the environment. If etchers are allowed to use traditional methods with copper, then it should be recognized that the use of this copper sulfate mordant is of no greater danger to the environment. It certainly is safer for the printer to handle.
Etching of Zinc
If the bath is to be used for both aluminium and zinc, then the addition of sodium bisulfate is necessary. If only zinc is to be etched, then the weak form of sulfuric acid is not essential, as the zinc chloride produced in the reaction is soluble in water and does not form a gel. Since all of our students now use only the cheaper aluminum, our experience with zinc is somewhat limited, but more than enough to have tested the process.
Understanding the Chemical Reaction (Dr. Bader)
In chemical terms, the etching/dissolution of the metal from the plate is an oxidation reaction... requiring the concurrent reduction of some other species. Which species is oxidized and which gets reduced (a loss and gain of electrons respectively) can be determined qualitatively from the electrochemical series, reproduced in part below, and oxidation/reduction can be quantified by calculations involving reduction potential data.
Reduction Reaction Potential (volts)
Cu2+ + 2e- = Cu (metal) +0.34
2H+ + 2e- = H2 (gas) 0.00
Zn2+ + 2e- = Zn (metal) -0.76
Al3+ + 3e- = Al (metal) -1.66
The negative sign for zinc and aluminum means that they resist undergoing the reduction reaction written, and rather prefer the reverse, oxidation reaction when placed together with hydrogen ions H+ (the active ingredient of acid solutions). The hydrogen, having a greater reduction potential, undergoes the necessary concurrent reduction. In short, the metals dissolve in acid! As the process takes place, bubbles of the hydrogen produced can interfere with further acid-metal contact, thereby stopping the reaction.
Conversely, copper which appears above hydrogen in the table does not dissolve in (is not oxidized by) just any acid... rather, nitric acid is required to provide the extra oxidizing ability of the nitrate species. This shows why this mordant does not work with copper plates.
In the same sense that the H+ dissolves metals below it in the table, the Cu2+ ion in the solution is able (even "more able") to dissolve metals below it in the table. The result is the dissolution of the aluminium or the zinc, and the production of copper (as the dark, finely divided metal) in place of the bubbles of hydrogen. This metallic copper produced could also interfere with further reaction, were it not for the fact that the solution can still work through the wet sludge, and further, that dissolution by acid is still occurring (to a lesser extent) at the same time, producing small hydrogen bubbles on the finely divided copper - which carry it away, avoiding further interference with the dissolution of the aluminium. The result is the noted clearing of the etching site, very little loss of acid content, and considerable loss of copper ions from solution -- appearing as copper metal.
The aluminium removed goes into solution as the aluminum ion, which requires fairly high acid strength to prevent the formation of gel-like aluminum hydroxide. The relatively slow loss of acid maintains this desirable condition - assisted by the fact that chloride ions (from the sodium chloride) form fairly stable, soluble complexes with the aluminum ions. Eventually, of course, the solution becomes "over-loaded", and its high ionic strength works against further reaction.
The sulfate which came from the copper sulfate and the sodium bisulfate is a necessary artifact of the use of these inexpensive and available substances. At best, it is non-participating, at worst it contributes to the overall ionic strength of the solution and its eventual exhaustion.
If it is necessary to revive the solution, or to maintain a constant copper content over a period of time, it would be useful to use a simple color comparison technique. Addition of copper sulfate to re-establish the same color in a side-by-side comparison will ensure similar copper content.
Reference has been made throughout this paper to "sulfuric acid". The acid present is, in fact, the hydrogen sulfate ion (HS04-)which can be considered to be the result of "partial neutralization" of (strong, dangerous) sulfuric acid. The noted pH of around 2.5 is consistent with the presence of this bisulfate ion, often described as a "fairly strong" weak acid. While strongly acidic conditions are thus avoided, the solution is, nonetheless, quite corrosive (witness the fact that it dissolves metals!) so that drips, splashes and spills should not be ignored. The solution is less dangerous than the more usual etching acids with respect to skin contact, but eye contact is still very dangerous. The wearing of safety glasses is strongly advised. The potential for the staining and corrosion of studio facilities is not an inconsequential factor. Clean-up is probably best accomplished with plain water, which dilutes the solution without allowing large amounts of aluminium hydroxide to form, which would produce white smears.
Creating large etchings has been a costly endeavor because of the high price of copper and zinc. With the bold abstract designs being created by many artist/printers today, the undesirable characteristics of aluminum might not be a concern for producing that kind of image. Since commercial aluminium can be purchased in sheets up to 4'x12', the size of the image is only limited by the limitation of the printing press itself. These, along with the following attributes of the method, make it a viable option:
1/ The cost and availability of the chemicals used to make the mordant makes this process less expensive and much less troublesome in acquiring the materials.
2/ The non-hazardous nature of the chemicals involved makes it safer for the studio, specifically in the classroom situation.
3/ Disposal of spent etching baths does not require expensive environmental control as all the copper compounds are removed.
4/ The color intensity of the bath is a good indicator of the strength of the solution, so that timing of the etch can be more accurately estimated.
5/ The more consistent action of the mordant over the life of the etching bath gives the artist more control over the plate.
6/ Open bite areas produce deep blacks without the need of aquatinting.
It is hoped that teaching institutions adopt this process for not only budgetary considerations for their respective departments in the cost of etching chemicals and disposal expenses, but for the cost of metal plates to their students.
References and Notes
Semenoff, N. and Christos, C., Using dry copier toners and electro-etching on intaglio plates, Leonardo, Vol. 24, Number 4, pp. 389-394, 1991.
Permission to photocopy this paper is given by the authors. Publication without permission is prohibited. Send inquires and comments to:
Nik Semenoff, Artist-in-Residence,
Department of Art and Art History,
University of Saskatchewan,
Saskatoon, Saskatchewan, Canada. S7N 5A4
e-mail address: <email@example.com>
Note: This paper in a slightly different version has been accepted sometime ago and published by LEONARDO, the international refereed journal of technology in the arts. LEONARDO, Vol. 31, No. 2, pp. 1333-138, 1998.
Using Copier Toners for Both Negative
and Positive Intaglio Images
By Nik Semenoff
In 1985, I found that dry copier toner could be used for producing tusche like washes in lithography, without the fear of overworking the plate or stone. On farther work with that material, I found it useful for imaging on mylar and exposure to photo emulsions to be processed in all media. Being a plastic, toner had some interesting characteristics that made it useful for various techniques within printmaking. I incorporated its use into the student work at our university, seeing that freer images would be the result. While positive photo plates and screen emulsions allowed us to use the toner images, our concern about the use of KPR materials had prevented its use in intaglio. The masters student at the time, had access to commercial photoengraving plates at the undergraduate school she had attended, so Christine Christos proceeded to use toner on mylar for her intaglio work. I tried a more direct approach to the use of toners in intaglio.
Presensitized photoengraving plates are expensive and out of the reach of many students. For this reason, I experimented on a more direct use of toners on metal plates. There are two methods of working directly on plates, one producing a positive image, the other a negative one. To produce a positive image, it requires the application of a resist coating over the toner.
Toners are manufactured mainly from plastics, the types used varies with the maker of the machine and the model number. You will find that there are two basic types, which I have classified simply as type A or B. This important information will give you greater freedom in manipulating the image. To find out the nature of your toner, place a small amount in a saucer and apply any common hydrocarbon solvent such as a paint thinner. If the powder forms a soft ball, it can be classified as type B toner. Type A toners are not affected by simple hydrocarbon solvents and retain their individual particles. It is also possible that some toners will fall somewhere in between the two major types. You should also test your toner with other solvents that will likely be used in making the plate. I would suggest common alcohols, plus some of the stronger solvents. Alcohol can be used with many as a drawing fluid, while stronger solvents will be used to remove the toner.
Because water is the commonest drawing medium, the toner will have to dispersed with a wetting agent. Use a few drops of any dispersant in about 30 ml of water. Add toner to twice the volume of the water and shake in a closed container. The toner can then be diluted in a saucer for use as a tusche-like wash. If for any reason you do not wish to use water, type A toner in a hydrocarbon solvent or a type B in alcohol can be used for your washes. The reticulation will vary with the type and amount of wetting agent in water washes; also, alcohol and hydrocarbon washes will be different from water.
After the wash has dried on the plate, it has to be adhered to the surface for farther processing. For intaglio, I would recommend the use of heat to make sure the plastic has melted sufficiently to produce a good bond. If the hot plate doesn't reach a high enough temperature, I use a small propane camp stove and a hand vise to hold the plate. Do not overheat the plate as the plastic will flow at too high a temperature and close up in the dark areas.
After the toner image has been set on the plate with heat, diluted orange shellac is flowed over the surface to produce a very thin coating. The best material is flake orange shellac that is made up into solution by suspending some within a nylon stocking, in wood alcohol. After it has dissolved, remove the stocking, letting the solution stand until there is a definite separation between the wax-containing portion at the bottom, and the purer shellac on top. Remove the pure shellac carefully with a poultry baster, leaving the unwanted wax portion. To let you see how well the shellac mask has been applied; an alcohol soluble dye should be added to the solution.
Dilute the shellac with wood alcohol so that not too thick a coating is produced. You will have to experiment with this, as it is hard to explain the right viscosity; actually a very thin film produces the best results. Use a soft brush to flow the shellac over the surface of the entire plate, starting at one edge. Try not to go over any covered areas as this produces more problems than it solves. Let the alcohol evaporate.
The next step is to wash out the toner image without damaging the shellac mask. Remove the toner image with common turpentine, using a short bristle brush like those used for stenciling. If the shellac was dyed, you can immediately see the mask after the removal of the toner. When shellac is heated above 150 degrees centigrade, it changes from a thermoplastic to a hard, horn like material that can resist mordants very well. Heat the plate until the shellac takes on a golden brown color, indicating all the water in its molecules has been driven off. The plate is now ready for etching with the shellac mask acting as the resist. Use block out for any areas you want perfectly white.
Toner as a resist to produce a negative image
The simplest approach in the use of toner for etching is to apply the toner wash in a manner that it will become the resist in the etching process. This is a normal procedure in etching and should not be too difficult to handle for most artists. The toner image is set by heat for best results. Block-out is applied to the plate where needed and the metal is etched in your favorite mordant. Negative toner images tend to appear much darker in print than what they indicated in the drawing. Because of the very fine characteristics of toner, the fine particles may be etched away as they are under-cut by the mordants. Electro-etching is probably one of the best methods of doing away with this problem.
Etching the plate
Because of the very thin shellac mask and maybe some dust particles in the air, go over the areas you want perfectly white. Within the toner image, slight breaks in the resist will not make any difference and should not be a concern. Etch the plate very carefully and not too long as the shellac mask may be lifted in too strong a mordant. I have found that the lighter etched plates printed the complete range of tints better than a deeper etched one.
-Semenoff, N., Using dry copier toners in place of traditional lithographic grease tusche,
LEONARDO, Vol. 20, #1, pp. 71-77, 1987
-Semenoff, N. and Christos, C., Using dry copier toners and electro-etching on intaglio plates, LEONARDO, Vol. 24, Number 4, pp. 389-394, 1991.
Printing Intaglio Images with Water-based Ink.
By Nik Semenoff and Alan Flint
With today's concern about the dangerous materials in printmaking studios, any decrease in the use of toxic products should be welcomed by printmakers. Over the last decade, I have been successful in reducing the use of toxic materials in lithography, screen printing, and intaglio. While not as active in intaglio as the other media, as a teacher in an institution where many eager students can quickly make the studio hazardous, I feel it is my duty to find safer products. After discovering a safer mordant for zinc and aluminum that uses copper sulfate, common salt and a weak acidifier, I had been hoping to find an ink that could be liquefied and removed with water, yet become water resistant over time. I feel that I have found a method that allows the printer to easily grind their own inks, giving them more control over the characteristics of the product than commercial merchandise allow.
While visiting Alan Flint in his Hamilton studio in 1993, we discussed the advantages of water based inks for cleanup and less toxic fumes in the work place. We carefully thought about the characteristics needed for the ink, then looked at the possible binding media and pigments in the studio. One that we tried was Lascaux clear screen printing base, colored with Createx liquid pigments. The results were very encouraging and we both intended to continue with experiments. Alan's commitment to his printing establishment left him little time for research, and since I do not actually print intaglio editions, I only periodically thought about the results we achieved. With my somewhat limited research, I found that dry pigments would produce a richer print, yet it was easy to grind up a batch of ink with a spatula and a piece of plate glass. I discovered that the ink would not dry if kept in a closed plastic container, unlike commercial oil based ink that skinned over quickly. To prevent too fast drying of the ink while wiping the plate, I tried some acrylic paint retarder in a very small amount. It started to look very promising from the results of these tests.
To see if others could get the same results, I had one of our masters student look into the materials by giving her the screen base, pigments and various retarders to try. Since she was inclined to produce larger prints, I was interested to see if my concerns of premature drying would be a problem. To my pleasant surprise, she had no trouble in wiping even larger plates with the minimum amount of retarder. Not being much interested intaglio, she only did a few plates and went on to lithography and screen-printing.
I took up the challenge from time to time as I felt the materials pointed to a safer work environment. Since I was concerned that commercial products can change with the next order because the manufacturer is concerned with other matters, I was hoping to find a basic substance that would be available to printers. As I showed printers the results of using this ink, I was encouraged to forget about finding a substitute for the Lascaux screen base, and make the method known as a stepping-stone for others to carry on. Here is the results of my research in this area.
Grinding waterbased inks
Use Lascaux serigraphic medium straight from the container and add dry artists pigments from a reputable source. Grinding can take place with an ordinary spatula, but a proper muller would be of help in getting smoother inks faster. Make the ink quite stiff, much like the commercial oil inks. While no retarder or other additives may be needed, I have found that a small amount of acrylic emulsion retarder can be useful for larger plates. It also tends to effect plate tone, depending on how much is used. With little or no retarder, the ink tends to dry as it gets to be a very thin film, allowing the printer to completely remove any plate tone with a piece of wiping tissue. The ink in the lines is much slower in drying and will print normally. After wiping, I suggest you place the plate face down on your inking slab to minimize the evaporation of the liquids in the ink.
Unlike oil inks, one does not have to soak the paper very long. For rag papers with much sizing, just a few minutes are needed, for non-rag proofing papers, immersion for 2-5 seconds is enough. After blotting the wet surface, the plate is printed on an etching press. If the paper is soaked too long, it becomes water logged, allowing the water-based ink to spread amongst the fibers. The minimal soaking of the paper lets the prints dry faster, with less problem of curling.
Any unused ink can be stored in a tightly covered plastic container for later use. I have found the inks I mixed years ago to be fresh and usable, with no skinning or other defects. I also discovered that the finished prints become water-resistant after drying for some time, just like household acrylic paints. Since the Lascaux screen medium is made from a concentrated gel of acrylic resin emulsion with glycol added as thinner and retarder, it can be considered permanent for artistic purposes.
I would hope that this disclosure will encourage other printmakers to do more research into the materials and develop ink that will become standard for intaglio printers. This would make the studio less hazardous as cleaning the plate and ink slab requires only a bit of water. As I mentioned before, intaglio is not my chosen printmaking media and I only do some research in the hope of finding better and safer materials for use in the studio. I must thank Alan Flint for his encouragement for my continued research and his initial input into the use of the Lascaux product. His printmaking knowledge and enthusiasm became an inspiration for experimentation in this area.
In late 1999, while researching water-soluble ink for waterless lithography, I discovered a method of using commercial litho inks and modifying them into perfectly functioning intaglio inks. While the formulation seems a bit too complicated at this time to publish any information on it, I will be working towards a simpler method.
Alan Flint, Anti Press
239 Holton Ave. South
Hamilton, Ontario, Canada. L8M 2L8