The process of silkscreen printing is an ancient and relatively simple one.
I've found myself recently though having to talk people through the process and realising that explaining one element of the process simply begs a question regarding another. The premise is simple but I guess the execution - which involves chemicals and light and mechanical elements and computers and printers and all sorts - could do with some explanation. So here it is.
The process of producing a silkscreened poster for Send More Paramedics, from initial pencil drawing through to final posters.
The initial pencil drawing -- this was actually done over a year ago (this poster has taken quite a long time to get made!). I didn't make any sketches before this, I simply drew it straight out onto A3 220gsm cartridge paper using a 2H pencil (I use 'light' pencils rather than soft leaded 'dark' ones because I press on too hard and it makes erasing pencil lines a bitch).
The inked illustration. I use a variety of inking pens - from simple Pentel fineliners to actual brush and indian ink.
The illustration is then scanned into Photoshop where I play about with the contrast to give me nice, opaque black lines against solid white background. I can then delete all the white, leaving the black lines on a transparent layer, enabling me to do the 'colouring in' on a seperate layer underneath, meaning I don't have to worry about 'going over the lines'.
I decide on my canvas size (which fits the size of the paper I intend to buy), add the type and begin to play around with different layout ideas. I decide the background needs more blood so I physically spatter a sheet of A3 paper with ink, allow it to dry overnight, and then scan that in as another layer which I colour red.
I now have a digital version of the poster. I've assumed I can get hold of some dark grey paper to print this on, and it'll hopefully look something like this:
and I email a large version of the image over to Duncan 'Medic to check he likes the look of it. He does, and gives me the go ahead to begin the printing process!
I now produce four black and white hi-res images in Photoshop, each image corresponds to the layer of colour I will be printing:
and I take these over to a local printers about 15mins walk away to get them printed out onto transparency the exact size they will be printed on the poster (it's pissing it down with rain and I listen to the new Mastodon album during the journey). These are my film positives and they all 'line up' to form the final image.
A couple of days later I take a long stroll to Hobbycraft to purchase 300gsm card stock to print onto. Unfortunately, they don't have the colour I want and apparently the company that make it has discontinued it (!!) so I have to make a decision on alternative colour... After some deliberation I go with 10 sheets of Plum, 5 sheets of Forest Green, and 2 sheets of Coffee Brown. Each sheet is A1 in size and will fit 2 prints per sheet, leaving me some card to spare. When I get home I crop these all down ready to be printed on:
EXPOSING THE SCREEN
The first thing to do is 'burn' the screen. For those unaware of exactly what a screen is, it's a woven, porous mesh held tightly on an aluminium (sometimes wooden) frame. The mesh is very, very fine but will allow ink through it.
Using a device called a 'scoop', I put a thin layer of Azocol onto the flat 'underside' of the screen. Azocol is a photosensitive emulsion, meaning that I have to transfer the screen to a darkened drying cupboard in order to expose it to as little light as possible (this is also the reason I don't have any photos of the coating process!).
Once the coated screen is dry it's time to burn the image onto it, bringing us onto the exposure bed. The exposure bed is a large, horizontal glass plate which is vacuum sealable. I place my film positive for the first colour (in this case white) onto the glass bed, and place the screen on top of it. I pull down the rubber 'lid' over the exposure bed, lock down all the sealing clasps and turn on the vac pump. Once all the air has been sucked out the screen is essentially stuck very tightly to the glass plate and I can pivot the whole thing up into a vertical position:
(You might notice that the image being burned is actually the red blood spatter and not the white - I didn't take any photos of me exposing the 'white' screen but the process is exactly the same.)
Facing the now-vertical exposure bed is a powerful UV lamp. I close the door and flood the screen with UV light for 3 minutes and then turn it off -- what actually happens here is that even though the emulsion I coated on the screen is dry the UV light is required to 'fix' it.
By placing the film positive in between the screen and the light we have effectively blocked off certain areas of the screen, meaning they are exposed to less UV light. We take this exposed screen straight over to the WASHOUT ROOM!
The washout room consists of a big metal trough, where we position our screen. I then give it a moderate blasting with the pressure washer (which is fun to use because it's like a big gun) -- because the design wasn't exposed to as much UV as the rest of the emulsion (and therefore isn't 'fixed') the design washes out easily and the rest of the emulsion stays where it is leaving us with a perfect stencil of our design:
The screen then goes back into the drying room to dry off...
Once dry, the areas around the emulsion coated part of the screen are taped off - these will still allow ink through so need taping off otherwise ink will get into places we don't want it. The screen is then locked tight into our pivoting, weighted printing frame. The paper is then placed onto the flat area below, which has a vacuum pump attached to it and which sucks air through tiny holes meaning the paper stays put. The vacuum can be turned off by holding down a footswitch, so I cut it off the pump in order to make it easier to line up the paper and the stencil. I then put masking tape 'tabs' around the edges of the paper to make sure I align my paper the same each time.
I attach a squeegee - a long rubber block on a wooden handle - to the squeegee arm, load plenty of white ink onto the screen and 'pull' the squeegee along the screen, forcing white ink through the stencil and printing on our card:
The vacuum is then held off with the footswitch, allowing me to slide my printed sheet of card out which I then place on the drying rack. I put the next sheet of card in place (lining it up with the tabs), release the footswitch to turn the vac on, lower the printing frame and repeat the process until all our posters have the white layer printed on them:
RECLAIMING THE SCREEN
I then scoop up the excess ink to be saved in a pot (you use a lot more ink than actually gets 'printed' on the paper, since the ink also acts as a lubricant to allow the squeegee to slide across the screen) and remove the screen from the frame. Back into the washout room we go where I tear off all the masking tape and wash all the ink out. The emulsion will not wash off with the pressure washer, since it is fixed on there... so we use another chemical to remove it.
Pregasol is a clear, water-like liquid which we spray onto the emulsion. Using a stiff brush we give the whole thing a good scrub and the Pregasol begins to break down the emulsion - which can then be washed off with the pressure washer. Cleaning the screen is a bit of a pain in the arse but needs to be done well because if tiny specks of emulsion are left in the mesh of the screen, they will effect the quality of the next stencil. Once the screen is fully cleaned it goes back into the cupboard to dry.
There's a lot of details and technique I'm leaving out here, purely because I just want to get the basic process across but once it's dry, the process starts all over again with our next colour - coating with emulsion, burning the stencil, etc. etc
Here's some pics of the rest of the printing process:
You can just make out the next layer, the Glow-in-the-Dark ink... this is the first time I've used this stuff and to be honest it was a bit of a test as to how it would look. I was hoping it would be a bit more visible in the light but oh well. It still glows pretty good though!
Stage Three - printing the blood!
Stage Four - about to print the final black lineart...
The finished batch of dry posters, ready to be individually signed and numbered.
CHARM OF THE PROCESS
As you will notice from the basic principles of silkscreen printing, it is nowhere near as accurate as digital printing or even off-set printing, but the fact that each poster is entirely hand printed and has it's own individual variations and slight imperfections means that each poster is a one of a kind piece of collectable art.
There are only 34 of these posters and no more like these will be made, ever. I'll be passing them onto the band to sell at their Halloween gig at the Cockpit in Leeds on the 28th of October - considering the effort that goes into producing this kind of artwork they are sold for really bloody cheap! If you can't make the gig but still want to pick one up, I'll have a few to sell myself so I can cover the costs of producing them.