Most photographs can be converted to a format that allows them to be silk screened. The best photographs for screen printing will have a strong composition and high contrast. The photograph must be converted to a digital file, if it is not already a digital image. Then it must be prepared for silk screening, more commonly called screen printing. It will be converted to a series of tiny dots known as half-tone dots for the printing process. Black and white or color photographs may be screen printed, although it is much easier to work with black and white.
Choose a photograph to convert for silk screen printing. The ideal photograph will have a strong composition and areas of high contrast. A strong composition features a distinctive subject that reads instantly. High contrast photos have easily seen areas of light and dark, or strong colors. The photograph may be black and white or color. Try working with a black and white photograph first to master the technique. Color photos can be converted to grayscale (black and white) in Adobe Photoshop from the "Image" menu. Choose "Mode," then click on grayscale.
If your photo is on paper, convert it to a digital file. Scan it into Adobe Photoshop either as a grayscale or color photo. Save the file resolution for 200 to 300 pixels per inch. Click on the "Edit" menu in Adobe Photoshop and select "Color Settings." Set the dot gain to 30 percent.
Print the photo as a film positive on a piece of clear vellum paper. A film positive is simply the photo printed on a piece of clear paper used to expose the image on a silk screen frame. Use a laser printer rather than an ink jet printer, as ink jet printers are not set up to print half-tone dots. Hold down the control button on your computer keyboard and click P to print or go to the "File" menu and select "Print." Click "Screen" in the print dialog box. Uncheck "Use Printer's Default Screen" dialog box. Type in 55 in the "Frequency" box. Select the "Round from the Shape" pull-down menu, then click "OK." Click "Print" in the print dialog box.
Place a silk screen coated with photo emulsion face down over a piece of thick foam rubber that fits inside the screen. Put the film positive face down over a silk screen coated with photo emulsion and scotch tape into place. Cover the film positive and screen with a piece of 1/4-inch thick glass. Hang the halide light about 20 inches over the silk screen frame and turn on for five to 10 minutes. Check the photo emulsion instructions for recommended exposure time. Develop the image with a spray of warm water in darkened conditions. Blot the silk screen frame with newsprint and let dry. The frame is ready for silk screen printing.
It is possible to use other software programs besides Adobe Photoshop to convert photographs for silk screening, such as Corel Draw and Openoffice.org Draw. Execute the same tasks, setting dot gain to 30 percent, and setting half-tone dot frequency to 55 lines per inch. Output the photo on a piece of clear vellum on a laser printer to create a film positive.
Color photographs also may be printed with silk screen. Four film positives must be printed and four silk screens made, one each for yellow, cyan, magenta and black. The four colors must be printed in perfect register to recreate the photograph. This is an advanced silk screen technique.