Screen Printing

First published November 2013

I was out for two days this week on a screen printing course, and here is a quick rundown of the process.

Like with most things in life there are different ways of screen printing but they all work on the same principle, which is this:

Different elements or parts of a final image are placed in a fine mesh screen and then ink is squeezed through them onto paper (or whatever material you are printing on) sequentially to build up a final image.

What that means is that each print is an original made up of different elements.

The prints can all be printed with the elements in different positions each time or if you want, the elements can be placed in the same position each time.

Either way, each print is an original because each time you print, the elements come together in the final design and everything comes together in the printing.

Of course, a printer may make a run of prints from the elements and place the elements in the same position on each sheet each time. But that is missing half the fun of experimenting with different layouts on different prints.

I made twelve prints, of which some are just partial prints with a couple of the elements on them. I did that so I would have a record of the process.

First Get Your Art Work

First you need some art work. I took along some zebra images, an image of a bunch of flowers, and some text. Before I went on the course, I went to a copy shop and I had them printed onto acetate sheets.

It would have worked equally as well if I had had traced them onto tracing paper.

The important thing is that there should be areas where there is dense colour (preferably black) and some blank areas.

There were two of us in the class and it was helpful to listen my fellow student’s ideas.

He was more experienced in screen printing (I had zero experience) and he had some well-defined artwork and knew how he wanted the finished prints to look.

I had the elements but only had a vague idea of how I wanted to arrange them. And that was because I didn’t understand how the process worked even though I had read about it several times over the years.

I just needed to see it happening in front of my eyes.

The first thing we did was lay out the artwork and that was when I learned my first lesson, which was that using coloured images for the elements doesn’t work – not enough contrast.

After I explained my rather vague thinking about the final composition, the teacher suggested that I make a solid colour in the shape of the zebra and that I would then have the option to print my striped zebra layer on top of that.

I agreed to give it a go so I traced out the zebra onto acetate and then filled the outline with black acrylic paint.

I also painted a solid area with acrylic onto acetate to make another element for grass, and I made another element for some sky by rubbing charcoal onto acetate.

OK. The next stage was to prepare the screens.

The screen was made of thick, slightly flexible plastic stretched over a rigid aluminium screen. The plastic had tiny (very tiny) holes all over it through which the ink is squeezed.

The teacher explained that if a screen is damaged (by someone putting a foot through one, for example) then they send the screens to a firm in Glasgow that fits new screens to the frame. We agreed that in the days when most frames were made of wood, then it was easier to stretch a new screen in place, but with aluminium frames it needed a specialist to do it.

Some of the screens were five years old, so I guess that with care they last for many printings.

I had five different elements (striped zebras, solid zebra background, grass, sky, and some text) so the screen I used had to be big enough to contain the elements – about two feet by three feet.

The paper I would be printing onto was about A3 size (297 x 420mm) which is about 11 x 16 inches. I am mentioning this because before the course I had the idea in my head that there would be a correspondence between the size of the screen and the size of the finished print. But there isn’t.

The paper and the elements in the screen are simply placed wherever one wants relative to each other. As long as the paper is beneath the element one is printing, the element will print on the paper.

I squeegee’d a layer of light-sensitive liquid emulsion over the screen and then left it to dry. Once dry, I put the screen on the glass table of a large UV (ultraviolet) cabinet.

Then I took my separate art elements and arranged them on the screen.

The arrangement has nothing to do with the arrangement of the elements in the final printing stage… it’s just a question of arranging the elements to get them all on the screen with a good amount of space between them.

Then we closed the cabinet and exposed the screen to UV light. That bakes the emulsion except where the light can’t get through where the black bits of the art work are.

And that explains why coloured art work doesn’t work… it isn’t contrasty enough. The final revealed shape would just be a vague mess.

Now I took the screen and placed it upright in a trough and washed it down. Now I could see my design elements as the water washed away the bits of the emulsion that had not been baked hard by the UV light.

Where the emulsion was baked on, the holes in the screen were blocked up. And where the elements were placed, the emulsion washed away, the holes in the screen were open, and the ink could pass through.

Next up, dry the screen and then place it on the screen-printing bed.

This next bit was a complete surprise to me. I imagined we would squeeze a dribble of ink out of a bottle when we printed. But of course, it’s not like that. We have to decide what colours we want to use and to do that we have to mix them. It was very, very messy.

To print, you have to put some ink (actually artist’s quality water-based pigment) in a dribble across the the screen, hold the screen away from the bed and squeegee ink across the first element.

Place a piece of paper under one of the inked element, lower the screen and pull the squeegee across it. Bingo – first section of the final art work done.

Repeat with a second sheet of paper, but I was experimenting with different layouts so this time I placed the paper slightly differently.

Repeat for the other sheets of paper… or rather, repeat for all but one of them. For one sheet I decided to leave out the first ‘grass’ element.

Then clean off the ink and continue with the second element.

I still didn’t have a complete picture in my head of how any finished version would look, but I trusted that it would start to come together when the striped zebras inked over the other layers, and it did.

Here is one of the final prints.

Zebras

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