Step 1 – Preparing the Diazo Photo Emulsion Sensitizer
The bottle will feel empty. The sensitizer is a thick paste. This bottle does not come with a seal.
The Diazo Photo Emulsion Sensitizer bottle contains a very small amount of a thick paste that can sometimes settle on the side of the bottle. The bottle can appear and feel empty. However, it is not. It is absolutely necessary to add water to the sensitizer and completely dissolve the paste into water. Fill the sensitizer bottle approximately ½ full with water (tap or distilled water works just fine.). You should see a colour change in the sensitizer after mixing with water.
Step 2 – Pour prepared Sensitizer into Photo Emulsion
The Diazo Photo Emulsion should appear a bright blue prior to adding the Diazo Sensitizer. Thoroughly mix the prepared Sensitizer solution with the Photo Emulsion by stirring, not shaking. The colour will change from sky blue to a grassy green when the Photo Emulsion has been correctly mixed.
Step 3 – Properly mixed Diazo Photo Emulsion
Always store the sensitized emulsion in a cool and dark place. Shelf life for the sensitized emulsion is 4 weeks at 32 Celcius, 8 weeks at 21 Celcius and 4 months when refrigerated.
The following videos are part of a 5 part series on screen printing by Speedball. The first two (included here) explain the above process and how to use Diazo Photo Emulsion and Diazo Sensitizer; while the last video explains how to work with the Diazo Photo Emulsion Remover.