The photo emulsion method requires three things: a screen prepared with photo emulsion/sensitizer mixture. a film positive or a printed transparency a light source. Speedball supports this method with three products, the Diazo Photo Emulsion(a three year shelf life before mixing) Diazo Sensitizer which must be mixed with photo emulsion for the emulsion to work. Diazo photo emulsion remover which will reclaim a screen with minimal cleaning effort.