We start on screen printing in February 2020, pre lockdown. Before printing you need to save an image in Photoshop to print out onto acetate.

To create a halftone, open up image in Photoshop, select Image>Mode>Bitmap and select Halftone screen. A window will appear offering choices of dot shape and lines per inch. 

Match the resolution to whatever you set your file resolution to usually 300dpi.

For Frequency, opt for between 40 and 65 for a 90 mesh screen. The larger the dot the lower the frequency. The Angle is the angle at which the dots are positioned, 45 degrees is the default. Save as a Tiff file and print onto acetate. 

Preparing a screen

1. Place the screen paper-side toward you. Pour the light sensitive emulsion into a coating trough. Tip the lip against the bottom and with a single stroke, pull it to the top of the screen.

2. The screen should now go into a drying cabinet away from the light. Leave to dry thoroughly.

3. Expose the image on the light unit, don’t put the image too close to the edge of the screen. String needs to be placed in the well of the screen to increase the vacuum. After exposure (5 units) wash the screen on front and back, put finger onto hose to direct the water onto the screen. This will expose the image. Put screen at the bottom of the drying cupboard to dry.

Cover the yellow edges with masking tape, tape into the corners. Build snaps out of thick cardboard and stick with some masking tape onto the edges of the wooden frame. These stop the ink from sticking to the paper.

4. Make a master copy to use as registration. Print this onto tracing paper. The printing ink should be the consistancy of single cream. The squeegee should be bigger than the image size. Flood the image with ink and then make contact with the table, the squeegee angled at 60 degrees. Make three registration marks, two at the bottom and one down the side. 

Printing

Colours need to be printed from light to dark. So if printing a 4 colour print, yellow first, then magenta, next cyan and finally black.

Colour blend

Try a colour blend with two colours, mix the two colours at the bottom of the screen. The more the colours overlap, the more gradated they will appear. Flood the screen with the inks and then pull the squeegee
back following the flooding lines.

Monoprinting

Work directly onto the mesh with a brush and ink. Don’t put on too much ink. Acrylic medium can be used to create negative space in the ink. 

Using Posca pens

Pin a sheet of acetate on top of the printed master copy. Centralise the image under the acetate. Draw onto the acetate with lithographic pencil, Posca pen, black oil pastel, or black acrylic paint, expose acetate onto screen.

Thanks to great teaching from Adam Hogarth at City Lit, I’m just starting to get the hang of screen printing.