I've gotten pretty good at printing single color projects, but I thought I would challenge myself and learn to not only print on paper (which is slightly different than fabric) but also learn to use registration marks to print in multiple colors.
Since the silk screen stations at TechShop are set up for 4 colors, I decided to print a 4 color poster.
You will need:
4 Vinyl cut outs (1 of each color you want to print)
An ink spatula
4 colors of ink
Blue painter's tape
A wooden or cardboard spacer (will explain further in a future step)
TechShops come with a standard 4 screen printing station, which are usually set up for printing shirts rather than posters, so you may need to make a new printing platform.
I ordered a bracket that fits on our screening station and simply attached it to a scrap piece of plywood that is bigger than my paper.
The most important thing to remember when making a print with multiple colors is to leave one part of your print image in every screen (I left the word "Bork") to use to line up your screens.
A side note on my design specifically:
This was my first attempt at screening multiple colors.
Had I known then what I know now I would have made my screens (specifically the red and yellow screens) much larger blocks of color and simply layered the red on top of the yellow, and then layer the black on top of that instead of trying to line up all these complicated edges the way I did.
Live and learn :)
Once I had the 4 different files set up, I went to the vinyl cutter and cut them out (make sure your mirror the image before you cut!), weeded them, and put them on the screens.
I came up with this cheater way of lining up the different screens.
Since my file was made digitally, it was very easy to print it out to size using the large format printer.
Once I had my image printed, I cut it out and taped it to an extra piece of paper I was planning on printing on later to make sure everything would be centered.
To do this, I put the printed out poser on the platform and lowered the first screen over it, moving the printed screen around until the word "Bork" lined up with the vinyl cut out words.
(The second picture is a bit hard to see, but I had the "Bork" lined up)
Once you have the first screen lined up, tape down your printed poster to the board and line up each of your other screens.
Once all your screens are properly lined up, tape off the part of your screen you were using as a registration mark on each screen except the screen of the actual color you want for that part.
Registration tabs are these neat little metal pieces that help you to line up paper when you are printing multiples of anything.
To use them, simply line up 2 in each of the bottom corners of your paper and tape down the outside tabs to the table.
I also added one on each of the long sides of my paper so I know they will line up properly.
Once you have the outside tabs taped down, simply remove the paper and tape down the bottom part of the metal tabs to the table as well.
The last step before you start printing is a step that is specifically for printing on paper, wood, metal, or any other material that will not immediately soak in the ink like fabric, and this is to put a spacer (approximately 1/8"-1/4")between the top of the paper and the bottom of the screen.
Since the ink does not soak into the paper the way it soaks into the fabric, the space helps prevent smudges and bleeding.
Most people use cardboard or thin pieces of scrap wood to make their spacers. I happened to have a wooden ruler that was the perfect height for my set up.
A good rule of thumb to use when deciding on what color order you want to ink your posters is to start with the lightest colors and work your way to the dark, especially when you are creating layers like on my poster.
If you wanted to experiment with opaque colors, then start printing from the background colors and move forward through the layers.
I inked approximately 30 posters, and I found it to be much easier to do all of one color, then go and wash the screen and squeegee before starting the next color.
Although you could use a flash dryer (most TechShops have one) and ink all 4 colors on one poser at a time, I was worried the ink would set into the screen too fast. Also, I would be stuck cleaning all 4 screens at the end rather than getting to clean one at a time.