electrolytic etching

This is a means of etching metal using an electric current, without using dangerous acids. It has taken a fair amount of experimentation with the techniques in order to get it to work effectively. Here is some information about how I have been doing it.

DISCLAIMER: I take NO responsibility for any accident or injury caused by trying this out. What I have given below is my own personal experience. It is up to the user of this information to ensure that health and safety considerations are implemented. Voltage plus liquid can be deadly.

UPDATE! I have experimented a bit with the electrolytes for steel and have found an even cleaner electrolyte: see table at foot of this article.

1) Prepare the metal

The metal must be completely clean and grease-free. I prefer to use polished metal as the resist seems to stick most efficiently to this. Silver (and many metals) are sold polished and covered with protective film. If you have metal like this, remove the film and simply wash with detergent and a soft bristle brush: dry the metal with hot air.

After cleaning, do NOT touch the surface with your fingers and only put it down on clean paper sheets.

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2) Mask/Resist

For this example, I am going to be using a material called "Press 'n' Peel Blue", which is sold in sheets. To create the resist, you put the material through a photocopier or laser printer and print/copy your original artwork onto it. It is sold for use in making circuit boards, so it is very accurate. Unfortunately, the instructions which come with it are plain wrong. They don't work, and several other people have confirmed that they have had problems, so:

1. a) Clamp an iron in a vice, or use a controllable hotplate. I use an oven thermometer to ensure that the temperature is set to 300 degrees.
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3. b) Clamp the metal onto the iron or hotplate. You can see that I have cut this strip of silver to have a long tang on it for connecting to the power supply. Allow the metal a moment or two to heat up.
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5. c) Cut out the pattern, leaving a tag to hold it by. (Remember that the artwork must be printed out in reverse!)
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7. d) Use a polished steel burnisher to rub the pattern down onto the surface of the metal. Do not press to hard and use gentle, circular motions, ensuring that you cover every part of the pattern. It really helps to heat the burnisher up on the hotplate first. The pattern will go from grey on blue to evenly black on blue when it is fully transferred.
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9. e) Leave the pattern to cool. Don't quench it in cold water. The transfer will be much more successful if you leave it to air-cool. After it has cooled, peel off the blue backing very gently.
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11. f) Mask off all other areas of the metal, such as the tang and the reverse. Good-quality parcel tape does this job perfectly. It can be cut to shape on a cutting mat with a sharp scalpel. This piece is now ready for the etch.
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Other resists can be used: beeswax applied to the hot metal and allowed to cool before scraping off; asphaltum-based grounds for fine art etching; dry transfer lettering; sticky-backed waterproof plastic; etc.

Experiments with pigment markers, resist pens and wax pencils have proved unsuccessful.

For an interesting use of a lasercopy as a resist, look at the Steampunk Workshop website. A colleague has described a method of improving on this by removing the heating element from the printer and removing the paper before it goes to the second set of rollers which straighten out the paper, but I have not had time to experiment with this.

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3) Etch

Very simply, attach the item to be etched to the anode (+ve) terminal of the current supply. Use the electrolyte, cathode and voltage from the chart below.

Turn on the power and wait.

It really helps if you gently agitate the solution: the etch will be much more even.

(Pictures to follow.)

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4) Clean

Every so often, take the plate out and rinse it under very gently running water. Check the plate to see if it has etched deeply enough. If it needs more etching, return it to the solution, reconnect the current and continue. When it has etched deeply enough, remove it from the solution and wash off any residues. Remove the parcel tape and the resist.

"Press 'n' Peel" can be removed with a fine wire or glass-fibre brush. Other resists will need chemical stripping or gentle heat followed by degreasing.

Finished etch:

(Better picture to follow.)

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5) Table of electrolytes and voltages

For a plate of around 20 x 20 mm, back masked.

(1) The cathode MUST be about the same size, or slightly larger than, the anode.

(2) In all cases, it is beneficial to lower the voltage and increase the time. I have read of etching small plates of silver at 0.2v for 24 hours, but have not tried this.

(3) For larger or smaller plates, the times will vary as it is the current density which matters.

(4) Silver nitrate, 0.1%, acidified with about 0.05% of concentrated nitric acid.

(5) 50g copper sulphate + 50g common salt per litre, acidified with 3ml/litre of sulphuric acid. This produces a thick and very cloudy residue as it etches.

(6) 100g copper sulphate per litre, acidified as (5) above.

(7) Can be etched for half the time at 8v, but tends to lift the resist.

(8) See note (7) above.

(9) Saturated solution, acidified with 3ml/litre concentrated sulphuric acid. Ferrous sulphate is sold as a plant food for azaleas.

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