HOW TO SCREEN PRINT

This guide is intended to be used by anyone who is keen to understand and has the patience to learn the art of screen printing. It is a home user’s guide and the advice is intended for folks without access to a professional studio like myself so the steps outlined in this document may differ slightly from those practised by professional artists but fundamentally the process remains the same. Screen printing is a skill that is learned over time and through much trial and error but once you have found your feet I hope that you get as much pleasure and satisfaction from your results as I do. Above all, have fun!

I print fine art and illustration images onto paper but these instructions can be tailored to suit those that print onto t-shirts. The main differences are that the inks will be material based and the printing surface will be a platen not a table. Once you have your cheap home built studio set up as per my post Screen printing Equipment then you’re ready to go.

ARTWORK

The first priority is to design the image that you want to print, decide on the size of the image and the number of colours you want to use. For those starting out the fewer colours means a simpler print to organise and manage. I design everything digitally in Adobe Photoshop on my PC. The main thing to remember at this stage is that each colour needs to be printed as a black image on to a sheet of acetate film.  I’ve decided on a 3 colour print of black, deep pink and mauve. So in my example I have to make and print out 3 different separations on to acetate film for each colour from my laser printer.

Final design for print created in Photoshop

Black Separation

Mauve Separation

Pink Separation

This film will eventually lie on top of your sensitised screen during exposure. In the above example the black separation for print can either be designed using full areas of black or with halftone dots:

Detail of final artwork for the black colour showing full black and full white areas (not used in my example)

Detail of final artwork for the black colour using halftone pattern to simulate tonal areas. This effect is generated in Photoshop which I’ve used for my print

PRINTING ON TO ACETATE FILM

To print I use a Brother HL2037 but am reliably informed that Epson printers give the best results provided you set your print settings to ‘transparency’. Most times I have to triple up my films to make certain that no light can get through the black tone and therefore ruin the sensitised screen during exposure:

Acetate film for the black separation. Each section has been printed 3 times to increase the opaque quality of the film. I am looking to prevent any light from getting through these areas.

The film is organised and registered correctly on top of each triplicate before being taped together

Finally each section is then taped together with transparent tape

Once the entire image has been printed and taped together the same process needs to be repeated for each colour separation. Once all of these have been generated you’re ready to…

PREPARE THE SCREEN

Use the degreasing chemical on the screen by spreading it over with a rag on both sides of the mesh. Wash out with water thoroughly and allow to dry. Warning: if you’re doing this in the bathtub rinse the bath out immediately after to prevent any residual degreaser from remaining. Always use rubber gloves that go up to the elbows. Read instructions on the container carefully. If any chemical touches your skin wash off immediately.

The screen is degreased in the bath using a rag covered in the degrease paste. Always use safety equipment described above.

A hairdryer works well to dry the screen if you’re impatient! To coat the screen with the photo sensitive emulsion you must be in dim or blacked-out light because you want to prevent any UV exposure from sunlight or UV emitting light bulbs which will harden the emulsion on the screen. I find that a dim orange light bulb gives me just enough light to see what I’m doing.

Degreased and dried screen, photo-sensitive emulsion, trough and handy stirring stick!

Fill the coating trough enough to ensure that it spreads to both ends when tilted. Don’t make the mistake of adding too much or you’ll end up with a mess with the excess. Hold the screen in one hand at an angle of 45 degrees with the backside of the screen facing you. With the loaded coating trough in the other hand touch the spreading edge to the bottom of the screen and tilt until all the emulsion along the length is touching the screen. Then spread the trough upwards at an even pace and the emulsion will coat the screen. Your drying and dark area should be nearby.

Fully coated screen. This must be done in dim light

I lay my screen backside down on two pieces of wood either end so it dries print side up and cover with a piece of board. Then I lay black-out material over that.

Screen laying on wood blocks covered with board to dry

Black-out material is placed on top of board to dispel any light during drying process

Once dried, the board and blackout material is taken away under a dim orange lamp.

It should take around 4 hours to dry but I leave it overnight. Once the emulsion has dried the next stage is…..

SCREEN EXPOSURE

Once dry, take the coverage away making sure you are in dim/blacked out light using your non uv bulb. Exposing the screen using the correct timing and distance from light source takes trial and error but I’ve found that a distance of around 15” at 6 minutes exposure using a 500w halogen lamp on a screen of 19” x 24” gives sufficient results. Lay your screen reverse side up over a black non-reflective surface, preferably black foam but I find that black t-shirts work just as well. This prevents any light spill from accidentally exposing parts of the screen that you want to wash out. Lay the acetate reverse-side up on the centre of the surface of the screen. This ensures that the image will print the correct way round with enough space between each edge when pulling the print. Lay a sheet of glass over the acetate. The glass holds the acetate down well enough to make sure that no light spills under the black part of the film thereby spoiling the area that you need to wash out after exposure. The entire set up needs to be positioned centrally under your exposure lamp for maximum coverage.

Next turn your lamp on and time accurately. The light sensitive emulsion in exposed areas will react with the light and harden. The unexposed areas under the black part of the acetate film will remain soft.

Screen, acetate film and glass under exposure lamp

Once the time has elapsed turn off the lamp and continue to work in the dark or dim light for the stage of…

WASHOUT

I have kept my exposed screen in total darkness for up to 2 days before washing out with decent results but preferably I’d do it immediately after exposure. Unless you have a dedicated washout area, most home screen printers can use a decent power shower. In darkness or dim light, shower down both sides of the screen and let stand for 45 seconds. Next, shower the screen one side at a time to coax the emulsion from the unexposed areas of the mesh. I find that wiping a sponge across the surface as I’m showering really helps. It takes me about 5 minutes to washout a screen properly if I have stubborn areas that won’t come out easily. Washing out is an art that you’ll master the more practice you get. Once you’re certain that you’ve got all the unexposed emulsion out, hold up to your light source to see your results. You’re looking for clear areas where the acetate film was opaque over the mesh and solid areas of hardened emulsion that were exposed to the light.

Detail of exposed and washed out screen. The darker areas are hardened emulsion that were exposed to light. Lighter areas show clear screen where ink will be pulled through.

You can now let your screen dry or use your hairdryer on it ready for…

SCREEN AND PRINT AREA PREP

Once the screen is dry it’s important to check for any small holes or areas of emulsion that have come off when it shouldn’t have done. In these cases paint on an emulsion spot filler to cover areas to ensure no ink can be pulled through.

Spot filler has been used to cover small pin holes in the emulsion.

All 4 edges of the screen need to be taped with masking or gum tape to make sure no ink seeps through to your substrate (paper) from the screen edges. Attach the screen to your hinges on your printing table and make sure you have your paper stock within arms reach. You’ll also need your sponge, inks, rags and a spatula.

PRINTING YOUR COLOUR

If you use paper stocks of varying sizes, it’s always beneficial to tape a section of acetate onto your printing table to lay your colour on before printing on the paper. This ensures that you control the area of paper that is printed. Once the image is printed on the film, the paper can be slid underneath to the correct placement. For printing more than one colour this practice is essential to register each colour in alignment.

Acetate film has been taped from one side under the screen to print the image and therefore register the paper that has been printed with a previous colour. It can then be folded clear when the paper is in position.

The ink needs to have the consistency of double cream. Always use a retarder (medium) in the ink to prevent it from drying on the screen, I normally add 2 heaped table spoons to my ink cup and mix thoroughly. With water based inks I also add a drop of water to aid viscosity. To print the colour lay a strip of ink around 1cm in depth across the top edge of the screen making sure it will cover all printable areas when pulled.

Hold the squeegee at around 45 degrees behind the ink and pull towards the bottom edge using constant speed. The first print should be on your acetate film.

Once the print has been made, pull the ink back over the screen to flood the printable areas with ink while holding the screen up at a slight angle so it doesn’t touch the table surface, this will prepare the screen for the next pull.

The first rough test print is placed underneath the printed acetate for correct registering of colours. Acetate is then folded back over ready for ink to be pulled on to the correctly positioned paper. In this test example the black ink will overlap the top edge of the paper so my paper stock for the proper print run should be larger.

Acetate has been folded away and test print is in position for first pull of the second colour.

Repeat this process on to your paper stock for however many prints you intend to pull. You may notice that your ink will dry on the mesh after a few pulls or becomes clogged which will affect the quality of your print. In this case you’ll need to washout the screen with water and leave to dry before re-printing your colour. If like me you have little space to dry your prints and no expensive drying racks then you’ll need to lay them on the floor strategically. Hanging them on a line using clothes pegs is just as effective if space is an issue.

Next you need to…

RECLAIM THE SCREEN

Reclaiming the screen is the process that cleans all the exposed emulsion off the mesh once all your prints have been pulled and should be done immediately after your last print has been pulled to prevent a permanent stencil forming. Scrape all ink off the screen and back into your cup and carefully rip all tape from the edges of the mesh. Wash the mesh down with water to clear of ink. It’s extremely important to wear safety equipment at this stage: rubber gloves that go up to your elbows, goggles, a smock or apron and a respirator. Also, a well ventilated area is essential. The screen reclaim chemical that I use is mixed at 10 parts water to 1 part chemical but most screen print suppliers stock ready-made reclaim pastes that don’t require diluting. Always read the label on the containers for instructions on use. Use a kitchen pan scrubber utensil to work the chemical over both sides of the screen and leave to stand for 2 minutes. If any chemical touches your skin wash off immediately. To wash out just hose down with your power washer using warm water from a couple of feet distance and all the emulsion should fall off easily. Warning: if you’re doing this in the bathtub rinse the bath out immediately after to prevent any staining. After, use haze remover to eliminate any image ghosting created by the ink of the image that you’ve just printed on the mesh. Once dried the process of printing your colour can begin at degreasing the screen. Also clean the squeegee thoroughly with water.

Image showing half of the original stencil removed with the use of diluted strip liquid and a pan scrubber. Always use the safety equipment described above!
The entire printing process can be a messy one but the more you try it the more proficient you’ll become in avoiding mess and making full use of all available space. It can be frustrating when you don’t get exposure times correct and screens don’t washout properly but with persistence you’ll get it right and learn to enjoy your fabulous results. I hope you have fun with all your endeavours!

See also my post on:

How to build your own screen printing studio

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