Photo-Etching: Technician Corner - West Yorkshire Print Workshop

Our technician Kate Desforges has been spending some dedicated print research days in the studios recently, most recently exploring photo-etching. This time is hugely important to refine particular processes and try out new ones, ensuring that we can continue to offer a wide range of printmaking techniques to our community of printmakers, and importantly, to make sure that they all work! Imaginatively titled ‘Technician Corner’, Kate will be documenting her research in blog posts throughout the year. So here’s the first!

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What is Photo-Etching?

Photo-etching is an intaglio printmaking technique. It is a way of getting a photographic image onto a metal etching plate. The plate is printed using an etching press, in the same way as a traditional etching.

This process holds a lot of potential for artists who want to explore photographic image-making through analogue printmaking. We have had a lot of interest in this process recently from our members, so although it’s a process we already offer, I wanted to refine things a bit, and also to try it out on a copper plate – as I have previously mostly used zinc plates.

A lot of people get confused between different related photo-intaglio processes, such as photogravure, photopolymergravure, solar plate, direct-to-plate photogravure. All these are similar processes, but vary slightly in the plates used, and the way the plates are made. In this post, I’m focusing specifically on photo-etching – where a photographic image is etched into a metal plate using a mordant, (in this case Ferric Chloride).

My specific research on this day was to find out whether using the reverse side of an aquatint screen works as well as the printed side when exposed to the plate. Most books and online process guides say it is very important to make sure that the plate is in direct contact with the printed side of the transparency you are exposing. However this causes a problem in a communal print studio, as the aquatint screen (also known as a stochastic screen) is delicate and easily scratched, and also a very expensive bit of kit! So using the reverse side of it would help us to protect it from scratches in the future. I also wanted to try to retain as much of the tonal value of the image as possible in the finished print.

How do you make one?

This was my process:

I de-greased the copper plate using whiting powder and a little water to make a thick paste. This is important to ensure the photo-emulsion adheres properly to the plate.
In the dark room with red safe lights on, I rolled out the blue photo-emulsion (Photo-Imageable Etch Resist from Intaglio Printmaker) with a soft roller, and rolled out an even layer onto the plate.
I then put the plate into a light-proof hot air drying unit for 30 mins minimum, and cleaned up the excess photo-emulsion with a hot, strong soda crystal and water solution. (Wearing gloves of course).
Next, I exposed the plate to our aquatint screen for 12 light units. (An aquatint screen is a piece of transparent film with a fine random-dot structure printed onto it, also known as a stochastic screen. Ours is also from Intaglio Printmaker).
I then exposed the plate for a second time to my test image, printed onto transparency on our Large Format Canon TM-200 printer, for 8 light units. During the exposure process, light passes through the clear areas of the transparency and hits the emulsion underneath, hardening it. The black areas of the image block the light, and those areas stay soft. These are the areas which wash out during developing.
Still keeping the plate in the dark, I took it back to the dark room to develop. I placed the plate in a weak developing solution – 1 tsp of soda crystals (sodium carbonate) to 2 litres of water – and left it in for 5 mins. The darker areas of the image developed out, revealing the metal underneath, and the light areas stayed put.
Next, After covering the back of the plate with sticky-back plastic to stop it etching, and I etched the plate using Edinburgh Etch (ferric chloride with citric acid added) for 20 mins.
Lastly, I stripped off the blue photo-emulsion from the plate surface by immersing it in a hot, strong soda crystal solution.

So far, so good! Using the reverse side of the aquatint screen doesn’t seem to make any noticeable difference to the finished image, and I can see a good range of tones in the plate. Unfortunately, I haven’t had time to print it yet! So I’ll update this post once I have.

This was such a valuable day, both to refresh my knowledge of the process, and I can now tell members to use the reverse side of the aquatint screen to avoid scratches. Hooray!

If you’d like to learn photo-etching, we often run short courses, take a look at our courses page: https://wypw.org/learn-to-print/in-house-courses/

P.S. You might be wondering who the woman is – she’s the Adobe Photoshop woman! I’m not sure where the image originated, but it’s got the full range of tonal values, from 0-100% black, so its great to use for test plates.