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Rosalind Harrison Photoshopping for Photoetching

Rosalind Harrison introduces digital imagery into her photoetching.

As an artist-printmaker working in my etching studio and workshop with computer facilities, and lecturing part-time at Anglia Polytechnic University and Cambridge Regional College, I have experimented with a wide range of printmaking techniques in my own work as well as with students. My knowledge of both Fine Art Printmaking and Apple Macintosh computers has enabled me to combine and introduce some exciting new aspects into printmaking.

With the students I started by taking images from the computer and making photostencils on screens for screen prints. I have also tried simply using a photocopy or laser-print and solvent- transferring this onto a degreased zinc plate and biting it in nitric acid. To get a good layer of carbon from the copy to stick to the plate it is best to use a new dark copy placed face down on the plate with a piece of thin absorbent paper soaked in solvent on top, and then rolled very slowly through an intaglio press. Without using aquatint, a positive image can be used since the open bite areas will print white and the grain from the photocopy will act like an aquatint, giving a black area. The quality is very crude and a lot of detail is lost but it is very quick and simple and works well with some images. I was keen to find a way of putting more detailed images from the computer onto intaglio plates; having tried a few methods I have come up with one that gives a good quality image. I have been able to achieve fine detail with relative simplicity and convenience. The method employs a computer as a tool, which is an enormous advantage both in the creative stage as well as in the ease with which it is possible to make a half tone image in negative or positive. Images are created on the computer, printed out and then transferred to a plate coated with a photoresist bitten in acid and printed using an intaglio press.

Computer generated images
Photographs and drawings were scanned into my computer (Macintosh Quadra 700 with some extra memory and a flat bed Mirror 800 colour scanner) and manipulated in Photoshop (an image editing programme). Photoshop gives amazing opportunities for making collages of photographic and drawn images, either scanned in or drawn straight onto the image in the computer. Once the image is completed, it was changed to a negative which is easily done in Photoshop (by going to the Image menu then to Map and Invert). The exposure of the negative should be adjusted so that the white areas are light grey on the screen; this can be done by adjusting either brightness and contrast or replace colour (in Adjust in the Image menu). This is because some half tone dots are needed in the white areas of the negative to create a pitted area to hold the ink other wise you will get areas of open bite that will not retain ink when the plate is printed as an intaglio print. The images were printed onto acetates using a photograde black and white laser printer (Apple Laser Writer Pro). The images were printed out from Photoshop either as complete images or colour separations of CMYK. The half tone image can be as fine as 300dpi.

Plate preparation & transfer of image
The clean degreased zinc plates were coated in dim light with 2 or 3 thin coats of aerosol photoresist (RS positive photoresist- a fast drying resist for the reproduction of circuit boards) and then left to dry for 12-24 hours in the dark in a sealed box. Coating one's own plates gives flexibility of size and shape. The spraying should be done in a ventilated area or with a breathing mask on. Full safety regulations come with the product. The plates were exposed in a UV vacuum light box, which proved necessary for the finer half tones and larger images. For small images exposure without a vacuum, using a sheet of glass to hold down the acetate on top of the plate and a UV light bulb from an old insect attractor unit was adequate. A test strip should be done initially to establish the length of time needed for good exposure, but it did not seem to be too critical.

Once exposed the plate was put into a tray of developer (RS Universal Developer- 50g of powder to 1 litre of water) for a few minutes. The areas where the light has reached wash away when developed. After washing down with water, the plate can be put back into the developer for a another minute or so if it is not developed enough. When ready wash again with cold water and leave to dry.

Etching of plate
A test strip is a good idea for the biting. I used a medium to strong dilution of nitric acid on my zinc plates and found it possible to bite the plate and take a print then put it back into the acid if a deeper bite was needed. The photo emulsion coating need not be removed for printing, and washing the plate with turps does not remove or damage the photoresist coating. When enough biting has been done the coating can be removed with a dilute solution of caustic soda. Any other method of intaglio can be applied to the plate. Once the plates were completed, I generally left the coating on as it made no real difference to printing, although with certain colours of ink it made inking up not quite so easy as there was no contrast between ink and metal in white areas. One other thing I have discovered is that Edding 400 permanent marker pens can be used as a stop-out to protect areas against nitric acid.

Printing the plate
Printing the plates was done the same way as any intaglio plate. I inked the plate with a small piece of stiff card while the plate was on a hot plate then removed it from the heat and used scrim and then tissue to clean up the plate. I have found that hand wiping is not always necessary: this means gloves can be used for inking leaving hands clean for paper, blankets and press. This is useful for students as in their excitement and eagerness to print they invariably forget to use paper fingers. For registering colour separations, like printing any multi-plate print, I use the method of printing the first plate, leaving the paper in the rollers of the press, marking the position of the plate with bar magnets, removing the first plate and placing the second one in the same position using the bar magnets, then removing the magnets and rolling the second plate through, and repeating for each plate. There is plenty of scope for experimenting with different colours and orders of the plates.

Examples of my work will be on show at the National Print Exhibition 1997 29th January - 8th February Mall Galleries, The Mall ( Nr. Admiralty Arch), London SW1. The work was inspired by my travels in India around Leh, in the State of Ladakh in the North Western Indian Himalayas. The images for the photoetchings were compiled from photographs taken while travelling.
Radio Spares (RS) Photoresist is catalogue number RS 198-9651
Radio Spares (RS) Universal Developer is catalogue number RS 690-849

I am available for workshops or any queries.
Contact: Rosalind Harrison, Tel. & Fax. 01223 322635


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