Create a graphic design to print on masonite. Decide what size your design will be. Open a file on a computer in a graphics or word processing program. Use elements of type, graphics, logos, illustrations or photos to create your design. Print the design on a piece of clear vellum paper. This is a film positive.
In a darkened room, coat a silkscreen stencil on both sides with photo emulsion using a squeegee. The emulsion should be opaque but must not drip. Lay the stencil flat, face down in a dark place to dry overnight.
Cut a piece of foam rubber to fit inside the silkscreen stencil. Place it on a flat surface in a dark room. Lay the silkscreen stencil face down over the foam rubber. Place the film positive face down on the back of the stencil, centered. Put the 1/4-inch thick piece of glass over the film positive.
Hang the halide light over the glass and turn it on. Turn off after seven or eight minutes. Remove the silkscreen stencil and develop the image under a spray of warm water. Spray both sides until the image appears. Blot both sides of the screen with newsprint and let the screen dry in a well-lit or sunny area.
Decide how many pieces of masonite to print. Buy it precut to size, if possible. If not, buy large pieces of masonite and cut them to the desired size. Some hardware and lumber stores will cut for you.
Place a piece of masonite on a flat surface. Place the silkscreen stencil over the Masonite. Position the stencil so the design falls where you intend to print. Put a thick line of screen printing ink in the stencil on the end opposite you. The ink should run almost from one side of the screen to the other.
Use the squeegee to pull the ink towards you with a firm stroke. Lift the squeegee and start another firm stroke towards you from the opposite end of the stencil to insure a good print.
Lift the stencil off the masonite to check your print. Repeat for each piece of masonite in your print run. Clean the ink out of the stencil when finished.