Exposing A Screen
Exposing your screen is the last step before you begin printing, it is a process with a few steps and must be done fairly quickly from beginning to end, make sure to read through all of the steps so you have a good idea of what to do. If you are unsure, would like a quick run through or some help come and see a technician in the morning before you start and we will be able to help you with any part, or all of the process.
Preparing Your Acetate
Acetate is a transparent film which can be used in a printer, you can photocopy the image you would like onto the acetate if it is drawn on paper, print an image directly onto it or draw in marker onto the acetate. The printers are laser printers so use the correct type of acetate. Just make sure that the black areas of the image are dense so that light will not reach the parts of the screen which you would like to come out in your print, any dark areas will be the parts of your print which are printed in ink. You can make your image as small or large as you would like, just make sure it fits on the screen you have chosen.
If the image is larger then A3 you can copy a few sheets with different parts of the original image and sellotape them together. If you have multiple images you can place them on one large screen, when it comes to printing you can mask off areas of the screen with paper and maskingtape.
Preparing To Expose Your Screen
It is important to prepare everything for the next steps before you get your light sensitive screen out from the cupboard. Switch on the UV light to let it warm up and turn on the pressure washer. The pressure washer needs to be on at the plug and the dial on the machine must be turned on as well as the tap connected to the hose. This means once you have exposed your screen you can wash it straight away. You should also make sure that you have worked out which way to place your acetate, it needs to be flipped over so the image is printed the correct way. If you look at the image the right way around and then turn the acetate over this is the way you will want to place it on your screen.
Exposure
Now you are ready to expose your screen. Draw the curtain to make the space light tight and you can begin. Bare in mind that all of the screens in the cupboard are light sensitive so be swift when opening the cupboard to retrieve yours and close it immediately after, or when another student comes to use their screen it will not work. Place your screen under the lamp and put your acetate on top, you should also pop a sheet of perspex on top to ensure that the image doesn't move around. Keep an eye on the time using a phone or watch, five minutes for smaller screens is perfect but as they get larger you will notice that the lamp light won't reach all of the screen, to fix this move the screen every 2-3 minutes so that it is fully exposed, you may also add a few minutes to the exposure time. For the largest sized screen it takes about 6-8 minutes. Turn off the light when you are finished.
Washing Off Emulsion
Move swiftly to the washout booth, you can tidy up the exposure area after. Using the ear defenders is also recommended. Using the pressure washer on a medium-high jet wet both sides of the screen keep working over areas of the screen where your pattern is, flipping it every now and then. The pressure is changed by turning the nozzle. You will start to see your image appear as the emulsion is washed away, keep going over these parts until they are clear. Holding the screen up to the light you should see your image clearly, if not keep washing. If it is not working then you may have left it under the lamp for too long, this will mean you need to try again on a new screen.
Make sure to turn off the pressure washer when you are done - we don't want a flood!
When you are happy place the screen flat on a table to dry, this is important as it keeps the tension in the mesh even. Use gum-strip tape around the edges of the screen and on any clear areas/holes you don't want to appear in your final prints. Tear off the correct sized strip, wet it briefly in a pot of water and smooth it on. Now all that is left is for your screen to dry and it will be ready to go.
Screen Care
You can use your screen multiple times if you look after it correctly, washing all of the ink off after each use is key or it will block your screen, the easiest and fastest way to do this is with the pressure washer, start on a low-medium setting and you can adjust the power as you see fit but be careful no to go too high as this may 'blow-out' your image. As before leave it flat to dry and it will be ready for use again. When you have done all of the prints you need please place your screen, cleaned of ink, with all of the other screens by the washout booth for stripping so that other students can use them.