It was a bit complicated to figure out quite what was needed but we got some half gram Diazo Sensitizer which you mix up with Diazo Photo Emulsion then coat the screens, by screens I mean A4 sized wooden frames with a mesh in the middle.
Once you've done that you leave them in complete darkness until they are dry, This can take anything from an hour to overnight. The trick we found was to leave some emulsion on waste paper so we'd get an idea if it was dry without opening the drying cabinet. (The drying cabinet was a large cardboard box that a fan we recently bought came in)
The biggest challenge was figure out the exposure, most sites seem to recommend a 150 watt bulb but I was able to borrow a 500 watt halogen work light which did the job, if you have clear skies you can also expose with the sun in about 5 minutes but we were doing this around 6pm.
You then have to wash the screen so the design is transparent, pro’s have high pressure hoses but we were stuck with a sponge, same result but with a bit more effort.
Once we dried the screen off we used masking tape to cover the areas that didn’t include the design to prevent bleed where the emulsion might have been thinner and placed it on the T-shirt and put the ink on and used a squeegee (a long piece of wood) to drag it across the screen.
This is the nerve wrecking moment, if you spread the ink over the design too much you risk moving the screen and ruining the image but we found the first use especially needed a bit extra ink to go through but as soon as you lift the screen to check you’ll probably not be able to get it back exactly how it was.