Before you can screen print, you need to transfer your design to a printing screen - also called 'burning' a screen.

 

A popular and professional way of doing this is using photo emulsion, although there are other techniques you can use which are quicker/easier/cheaper that produce good results (such as using a simple stencil). This mini how-to covers using photo emulsion only.

 

Photo emulsion is a liquid that undergoes a reaction when exposed to light; UV light causes it to harden. Screen printing makes use of this ability.

 

 

- The first step is to prepare the design you want to be printed. You can do this by either drawing your image onto transparency film/acetate (a sheet of clear plastic) in black ink, or printing the image from a computer or photocopier onto the sheet. The idea is that the transparent sections allow light through, but black ink (as long as it's opaque) blocks light from getting through.

 

You can use your own technique for transferring your design onto the transparency if you wish; for instance, you could cut the design out of opaque black paper and stick it onto the transparency sheet, or draw the design onto the sheet with glue. As long as it blocks light out it should work.

 

You could also experiment with other materials like black lace, leaves or random objects like stationery items (paperclips, pins, elastic bands) for instance.

 

 

- Next you will need to add the photo emulsion to your screen. A screen consists of a fine mesh fabric stretched onto a (usually) wooden frame. The mesh used to be made of silk (hence the name 'silk screening'), but now it's more likely to be a manmade material (e.g. polyester).

 

The photo emulsion is applied to both sides of the mesh using either a scoop coater or a squeegee. The emulsion coating should be uniform and thinly applied, making sure there are no gaps/missed bits. Remove the excess emulsion and put it back in the container for re-using at a later date. Make sure you have newspaper laid down to protect your surfaces.

 

 

There are a couple of things you can do to make applying the emulsion easier:

 

* Add a push pin to each corner of the screen frame, on the flush side (were the mesh is flush with the frame). This is so that when you are applying emulsion to the other side (the non-flush side), you can rest the screen on the pins and prevent the mesh making contact with your work surface.

 

Or

 

* Have the screen leant up against a (protected) wall whilst you apply the emulsion. Just be careful of drips using this method though.

 

Make sure you do this step of the process well away from UV light and in a room with low lighting - the experts use a darkroom and special lightbulbs, but this isn't vital as long as don't dawdle too much :)

 

 

- You now need to leave the screen in a dark room (or cupboard or cardboard box) until it dries, preferably with it lying flat and with the flush side of the screen facing down. This can take a couple of hours or so. You can use a fan to speed up the process if you wish.

 

 

* Please note that the side of the screen where the mesh is flush with the frame is the bottom of the screen, whilst the other side where the mesh is embedded is the top.

 

 

- When the emulsion is dry, turn the screen over so that the bottom (flush side) is facing upwards. Take the transparency you printed/drew on earlier (which is also called a 'positive') and place it on top of the mesh. The positive should be placed upside down so when you look down on it it is a mirror image of the final design you want.

 

Use a couple of pieces of clear tape to keep it in position or place a piece of clear glass/acrylic on the top. If you use glass/acrylic, make sure there aren't any marks or dust specks on the surface.

 

 

- Now the screen is ready to be 'exposed' i.e. have direct light applied to it. You can use sunlight by going outside (even if it's a bit overcast) or you can use lamps. The method you use will alter how long the exposure time is. For instance, using sunlight or UV blacklights will take the least time (a few minutes) whilst 150W clear incandescent bulbs will probably take over an hour. It also depends on the screen size, so make sure you research/Google the timings and the distance that the lamps must be from the screen. Check the instructions on the photo emulsion product you are using too.

 

During exposure be sure that no shadows are falling across your screen. It's also a very good idea to put a dark surface underneath the screen - such as black fabric or paper.

 

If you leave the screen to expose for too long, light can get through your blocked-out design slowly and slightly expose - or expose parts of - the emulsion underneath. This stage of the whole process may take a bit of trial and error, but remember that if you make a mistake you can buy a 'photo emulsion remover' which allows you to remove the emulsion and start over again.

 

What happens now is that the areas of emulsion that have been exposed to light harden and bind onto the mesh, whilst the areas under the solid black parts of your design stay soft and can be washed away with water. So...

 

 

- The next step is indeed to wash the soft emulsion away with water, which will leave you with an area of emulsion-less screen that is exactly the same shape as your design.

 

You can do this step outside with a hose, or indoors in a sink or bathtub. It helps if you have a hose because then you can get some water pressure to remove the emulsion quicker. Rinse the screen thoroughly on both sides, making sure the emulsion has all gone from the area of your design. Hold it up to the light to check.

 

Don't use hot water for this, and also only remove the transparency just before you wash the screen; don't remove the transparency and then wait 10 minutes before washing.

 

 

- Leave the screen to dry.

 

 

You have now successfully burnt your design onto a screen, yay!

 

One last thing you may need to do before printing is to fill in any tiny holes in the emulsion that shouldn't be there. There may not be any holes, but if there are you can use (masking) tape or a screen filler/blockout product to cover them up.

 

 

The main alternative to this photo emulsion method is having your design cut out of a sheet of contact paper. For example, if you wanted to print a heart; you would cut the heart shape out of sticky-backed contact paper and then you would put the heart shape to one side and attach the rest of the paper to the underside of the screen. You make sure that all of the screen is covered with contact paper (and masking tape at the edges) to leave just a heart-shaped gap.

 

When the ink is spread across the screen in the printing stage, the ink can only go through the screen mesh in the area that has no contact paper covering it i.e. the heart shape - so this is the shape that ends up printed.

 

If you can't get hold of photo emulsion, or you don't have enough space to work in, this method would be a good choice. The contact paper technique isn't the best for detailed designs though.