The first thing you want to do is come up with the design you want to screen print. You can do multi-color screen-prints, but it’s best to start out simple.
I drew this picture of my dog using an old version of Adobe Photoshop. I started out with a blank image that was about 12×12 inches at 110 pixels per inch. I tried to have the image be the size it would appear on the shirt, and I chose 110 ppi, because I am using 110 count mesh in my screens.
The image you draw will be a black & white positive. The black parts is what is going to be printed on the shirts. It doesn’t matter what color you are ultimatly going to print the image in, the positive you are making MUST be black and white.
After I finished my image, and was satisfied, it was time to print it. To print my positives, I bought an HP Laserjet printer on eBay for $11.00. I looked for an auction that was by a seller local to me, and saved on shipping. I also bought a 25 pack of transparency film at the local office supply store for about $4.00.
I wanted to print the image larger than would fit on a single 8.5×11″ transparency. Photoshop doesn’t have this capability. There are software programs that would do this, but not wanting to plunk down $40, I looked for a cheaper alternative. After playing around, I found that the Excel spreadsheet program that comes with MS Office that I already owned, would do this. I just inserted an image from a file (my image). I formatted the image to adjust it to the exact size I wanted to screen print on the t shirts. I shrunk the margins so I could print the image on two sheets instead of four. I loaded a couple sheets of transparency film, and printed my image. Part of my image was on the first sheet, and part on the second. Using clear scotch tape, I taped the sheets together to make a contiguous image positve.
As an alternative, there is transparency film available made to work in ink jet printers, but it expensive. Another alternative is to use velum paper. I have read that either of these will not necessarily produce as crisp images as clear transparencies.