Practice: Photopolymer printing

This is a highly sustainable practice which uses no dangerous chemicals, and leaves the printing plates reusable. In Capileira, we used copper plates, which had to be cleaned- wet/dry sandpapered to remove any scratches- then deoxidised in a bath of salt and vinegar solution- then degreased (in soya sauce). Finally washed and dried.

The laminating process could be done wet or dry, and the important thing was to avoid exposure to UV light, as this is photosensitive film. The film could be cut larger than the plate, then floated in a shallow bath of water, where the underside of the film could be stripped of its Mylar coating (hold onto this Mylar for other uses). The film is them squeegeed to remove air pockets, then dried with a soft cloth on a dry surface, and all remaining air pockets removed.

The plate is then dried flat in a drying cupboard for 2 minutes. Then it needs to be stored in a box until ready to use. This is perhaps better done the day before exposing.

The image that will be printed is exposed onto the photosensitive film by means of a UV lamp and a stencil made on transparent or semi-transparent film. Timings are precise- seconds- and have to be calibrated using a test plate.

The first decision is whether this is an image that can be exposed directly, or whether it needs to be exposed through an aquatint screen.

For the first- direct exposure- the image must be a line drawing or a purely black and white image. It may be made up of hatching, but there are no half-tones.

For images with continuous tones, such as ink wash, gouache- then an aquatint screen- a layer of tiny irregular sized black dots- must be used first.

The image is developed in a washing soda solution, then dried in a drying cupboard. It can then be hardened in the sun before inking and printing.

The film is removed in caustic soda, leaving the plate ready to re-use.

This was my first attempt: an image on film, made with marker pen, chinese ink and wash.

IMG_3763

It didn’t come out well, because at this stage I didn’t know about the aquatint layer, so only the black lines came out, not the continuous grey tone.

IMG_3776

With an aquatint layer though, it still wasn’t great, and I tried selective developing, i.e. focussing on the grey areas when developing the film in washing soda.

I wanted to try getting pencil type lines, so used a litho pencil- an actual pencil would not be black enough. This is the image on film; litho pencil with ink wash, so again a continuous tone.

IMG_3764

The image was ok- I tried it a few times, and mixed it with a monoprint layer and mask, but still not getting real black blacks.

IMG_3779 IMG_3774 IMG_3769 IMG_3768

Then I experimented with masks and using photographs- this involved using photoshop to manipulate the image, which I am not good at at all, so is probably not something I will repeat, although the feather photo did come out well. There are other ways of using photos, with photocopies or scans- and even using oil to make a photocopy transparent- these things I have not yet tried. This image was a return to my favourite poem, as I made a couple of transparencies as masks, writing the words of the poem as I remembered them, repeating, crossing out, over-writing in a palimpsest.

This one was unsuccessful because the mask was not sharp- it was a pair of  actual feathers – but I could not put them under glass in case particles were sucked off in the vacuum unit, so just had to lay them on top. then a sheet with writing all over was exposed, but only the masked section would now be able to pick up the image.

IMG_3766

This was an actual photograph, which could then be used to produce a highly detailed print. This involved two layers as well, but reversed this time.

Photo printed on film
Photo printed on film
Mask - script on film
Mask – script on film

Black and white printed image with registration not quite right- I should have had a guide on my photo, but it was taken on a white background, which made registration difficult. At least here though, blacks are black and whites are white.

Black and white print
Black and white print

This is a colour version, my favourite image of the week:

Black and sanguine
Black and sanguine

This was one that didn’t work well as an image, but is a technique for painting on developer directly onto the aquatinted screen. You need to work in low light, quite quickly. It would work better at home I think- the washing soda developer was mixed at different strengths, but was getting mixed with several people using it.

IMG_3773

After returning from the course, I set about getting equipment for this- it’s not straightforward though. The film is specialist, as is the aquatint screen, and a UV lamp is expensive, although the sun can also be used. The materials are “everyday” yet it’s surprising how hard those “everyday” items like washing soda are to get hold of. I managed and had a good set up. In France. But too little time to use it. I succeeded in laminating plates and making masks while there, but didn’t have an aquatint screen for greys. (I forgot that I could still do line drawings!)

IMG_3668

IMG_3667

 

Postscript:

I brought back the film to Hong Kong, as well as washing soda crystals and other items such as the copper plates. But for some reason, the film will not adhere to the plates. All the materials are the same, and the film was kept cool. Frustrating, as I now have the aquatint screen too.

 

 

 

 

 

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Author: chrisocaprintingblog

Studying visual arts part-time with the Open College of the Arts

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