The Process of Screen Printing


Screen printing can be carried out at an industrial level as well as on a very small scale; even by total beginners at home. DIYers can make great use of this process and get professional results even without having to invest in an expensive setup.


Small businesses in particular make the most out of the flexibilty of screen printing by using it for varied custom print jobs; from branded packaging and t-shirts, to posters and stationery. Screen printing is brilliantly versatile in that it can be carried out with a few basic supplies and a small amount of space, and can be used for long production runs of thousands, or for short productions...even for just a single one-off product.


It's not the cheapest hobby ever, but I think the results are worth it...and it's a lot of fun too!


The diagrams below show you step-by-step how screen printing is carried out using the popular photo emulsion stencil method.


The Stages of Preparing a Screen:

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.


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Using the Screen to Print:

Now that the screen is prepared, the actual printing can now take place. This is the fun bit, but I think that the entire screen printing process is very rewarding and enjoyable.

- After you have burnt your screen you will be ready to start printing, so be sure to get your work surface (which should be flat and solid) cleared and ready to use. Put down a layer of paper to protect the surface from ink.



Note: If you are printing on fabrics (rather than paper or card) you'll need to use textile inks, and if you are printing on t-shirts you will need to put cardboard inside them to prevent ink seeping through to the back.



- The next step is to add tape all around the outside edges of the mesh in your screen, on both sides, to seal them. This is to stop leakage.


If you own a printing station/press then obviously that makes the printing process easier, but as this page is aimed at home use, you probably won't have any dedicated equipment like that. If you progress this hobby, then a printing station would be an excellent investment.



- Lay your paper/card/fabric down flat on your work surface, ready for being printed. If you still have push pins in the corners of your frame, remove them before you proceed. Position the screen, top side (where the mesh is flush to the frame) facing downwards, on top of where you want the design to be printed.



- Pour a blob of ink onto the screen at the end furthest from you. Use your squeegee or floodbar to pull the ink down the screen quite swiftly, making sure you press down and keep the screen in the same position.


It's helpful if you have someone else to hold the screen in place, or you can rig up some mechanism to help you if you are handy at DIY.


Make sure the squeegee you use is at least as wide as your design so that you don't miss part of it as you make the stroke. Some people hold the squeegee vertically and some hold it as a 45 degree angle. Everyone has their preference so it's best to experiment with both.



Note: An extra step you can add before the actual printing is a 'flood stroke', which basically refers to the first stroke you make with the squeegee to spread ink over the screen, without holding the screen against any surface. The flood stroke can help you get a more consistent print, and all you do is:


* Add the first dollop of ink on the screen at the side nearest to you and then use the squeegee to push the ink across the screen, only exerting light pressure and trying to cover the mesh evenly.


Unless you have some wooden blocks to balance the frame on, you'll might need a friend to hold the screen mid-air whilst you flood the screen with ink.



* Place the screen onto your fabric/paper and do the printing step which I outlined above; pull the squeegee back across the screen (pulling it towards you whilst applying pressure) in order to make your print.


Some people do this the other way around by pulling the squeegee towards them to make the flood stroke and then pushing the squeegee away from them to make the print stroke. Either way works and there seems to be a debate about which method is better - but just pick whichever you prefer :)


As the ink is pushed (or pulled) across the screen on the printing stroke, the ink will only go through the clear area where there is no photo emulsion. If you are using textile ink to print on fabric, you can heat-set the ink with an iron after it dries, and then it'll be permanent and washable. If you have printed a t-shirt, let the ink dry before removing the cardboard from the inside.



After you have finished printing OR after the screen gets too messy and is causing smudges OR if you just want to change the color of ink you are using, you will need to clean the screen. To do this you need to remove any tape from around the edges and then rinse the ink off with warm water (but be sure to scrape off any excess ink to save for later before you rinse). Leave the screen to dry before you use the screen again.



The above information onlys cover printing with one ink colour. If you want to add extra parts of a design in different colours, you will need to make a separate screen for each new colour. The final print is then built up by printing one color layer after the other with all of the different screens. The difficulty lies in perfectly lining up the prints.



So there you go; that's my screen printing summary.

I hope you found it useful!



An Excellent Video Summary:

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