1. What is screen printing and how does it work?
This is the process of putting ink colors on garments. A. The artwork must be color separated within the design going on the garment, if more than 1 color. Usually this is done by computer generated software. B. Light sensitive chemical treated mesh screens are prepared so each color separated part of the design can be burned onto a screen and lined up so the design matches the over-all alignment to complete the final design when printing on the garment with all the colors. C. When the screens are placed in the press, locked down, and lined up on a rotating pallet under each screen. D. The screen is placed down on the garment that has been lined up and straight on the pallet. The color of ink is put onto the upside of the screen and with a squeegie, the ink is forced through the mesh with the image that was burned into the screen previously. E. The garment on the pallet must be “heat flashed” with the ink in order to be able to have another color put on without smearing the first color. This step is repeated between each color until the last color sequence is applied. F. After the last color is applied, the garment is taken off the press and put into a heat conveyer to pass through a heating chamber for curing. It must reach a certain temperature range to “set” the ink in a permanent state, i.e. “Cured”
2. What type of ink is used?
It’s normally called “plastisol” ink. It is an oil based ink, has a very long shelf life if stored between 40 – 90 degrees. This is why the finish garment must be cured to be able to touch and not smear on to other things. The ink can mixed together with other colors to get different shades needed. This ink is design for 100% cotton and 50-50 poly/cotton. An additive is needed for nylon products.
3. What happens to my artwork and screens?
The artwork is saved on a clear plastic sheet called vellums. The vellums are printed on a computer / printer as a single color, black image. It is then used to put on the light-sensitive mesh screen to burn the image in. The image is also saved on the computer for back-up. After printing the garments, the screens are cleaned (the ink taken off) and either re-inked with a different color or cleaned for storage for later use, with the image still burned on the screen. They can be completely cleaned and re-chemically coated and stored in a darkroom area for the next order.
4. How many colors can be screen printed at a time?
Usually up to 4 or 6 on manual presses. On larger automatics, up to 12 as a rule. Most everyday prints are 1 to 4 colors, mainly because of the cost. The colors are endless because the ink can be color matched, even with custom mixing to get the desired effect.
5. Why are the set-ups more expensive for this process than others?
The images have to be put onto separate screens. Each color in the design to be printed needs it’s own screen and each size print needs it’s own screen. Screen prices run anywhere from $15.00 to $25.00 depending on the vendor The screens are the biggest factor in the set-up charges.
The final cost per garment is cheaper if the quantity is larger, and often the set-up can be offset by larger volumes and constant reorders. The ink prints get cheaper, the more that is printed per set-up. Overall, the cost of printing less than 12 is more expensive than is the printing over 36 or more because the set-up cost the same no matter how many are printed.