SPEEDBALL-Speedball Diazo Sensitizer. The photo emulsion method of screen printing is the most exciting method created! Just use a screen prepared with this photo emulsion/sensitizer mixture, a film positive or a printed transparency film, and a light source that will transfer the opaque images of your positive to the light sensitive printing screen. This package contains one bottle of Diazo Sensitizer. This Diazo Sensitizer must be mixed with Diazo photo emulsion. Conforms to ASTM D4236. Made in USA.