How to Screen Print Signs and Stickers
Graphic printing consists of many types of screen printing that are not on a textile surface. This could involve coroplast, aluminum, or metal signs, vinyl stickers, posters, wood surfaces, acrylic, plastic, rubber, and many other different types of substrates. There are some main differences in the processes and supplies used between textile screen printing and graphic screen printing.
This page is designed to help inform of those differences in this type of screen printing.
First, there are different types of inks used for most of the different types of substrates you are printing on. One of the main differences between graphic screen printing and textile printing is the ink.
Graphic screen printing ink does not need to be heat cured. There are two different types of graphic ink, solvent based air dry ink, and UV ink that has to be cured by a UV reactor. Because UV reactors and the presses used for UV printing are large and very expensive we primarily sell and recommend starting with a solvent based ink.
Solvent based inks have to be thinned with a specific thinner formulated for that type of ink. Solvent based inks are also mostly air dry inks. This means that you do not need to heat cure the inks after they are printed. However this also means that multiple color printing cannot be done simultaneously. For a multi-color print you must print the entire stock of first color, let dry, and then print the following colors in that same fashion.
Here are some basic graphic printing instructions that will explain more in detail how the process works.
Place the press on a flat table or bench. For best results clamp or screw through the press to the table top to secure the press for production. Taking your exposed screen, center it lengthwise into the screen clamps and tighten down with hand force only. Take your film positive and place it where you want your print on the corex. Tape it down. Looking down from the top of the screen, line your image up with the stencil on the screen. You will be able to see the positive through the screen, so line up until the stencil on the screen is all black. Tape your corex or substrate onto the press base using masking tape, on the right side as well as the top side. About a 4 piece on each side will do fine. Now you will need to create some bump guides. The guides need to be about 2 long and an inch wide. You will need a total of 3 pieces. Put double-sided tape on a scrap piece of corex and cut to size. You can also use cardboard, thin wood etc. The guide just cannot be taller then what you are printing. Place one guide on the left side, five inches up from the bottom of the piece you are printing ( left side ), carefully place it right next ( touching ) to the piece you are printing and tape it securely to the base. Do the same at the bottom placing the guide about 3-1/2 in from the left bottom corner. And place the third guide along the bottom as well about 10 from the left bottom guide, again securely tape it to the base. With these bump guides in place, when you slide your material into them, it will print in the same location on every piece. Open your container of ink, and place 3-5% ink thinner in it and stir well. It may be easier to mix in a separate container. Only mix as much ink as you need for the job at hand. Get your squeegee and put it in your screen, leaning it against the back frame. Have your material you are printing stacked up next to you on your right side. Also have a place on your left to place the signs when you take them out of the press, keeping in mind they will be wet when they come out and cannot be stacked on each other. Put your first piece in place sliding into your guides Pour some ink into your screen right in front of your squeegee. Flood coat your screen, in other words pull ink across the screen with very little pressure, ( the screen is in the up position ) you want to cover the screen with layer of ink, but not put enough pressure to push it all the way through your stencil. Lower the screen and either push or pull (your preference) the squeegee across the piece you are printing, using enough pressure to clean the image area of ink. Immediately re-flood the screen with ink. Pull your first piece you have printed out of the press and do a quick look over it. Place it in your drying area put the next piece in and repeat the print process and so on. Remember your ink is air dry so you need to work at a fairly quick pace. If your image is getting fuzzy or rounded on the corners your screen is drying, when this happens you need to clean only the image area from the bottom of the screen and then continue. I you are only getting a few prints and this keeps happening you may need to thin your ink more. If you are printing a multi-color print, after the first color is complete, completely clean the screen, squeegee etc. Un- tape your bump guides, place the new screen in the press centered and this time set-up to one of the pieces that you have printed, again using the bump guides in the same places. When you are done do a complete clean-up and store all your materials in a cool dry place.