Before Exposure Water-resistant diazo emulsions have a higher proportion of PVA, which provides greater water resistance. Plasticizers are commonly used to give an emulsion flexibility and mechanical resistance. A wide variety of plasticizers are used in emulsions, depending on the performance characteristics required by a specific formulation. The more plasticizer in the formulation, the more flexible the emulsion. Diazo sensitizer is supplied as a powder or syrup.
Syrups are easier to dilute, but powders are more stable.
Both perform equally well when mixed into the emulsion. Diazo is an excitable, rather unstable substance. It is most reactive with UV light, but heat and water will also set it in motion. Diazo will begin to degrade from the moment it is mixed with water, so it should be added to the emulsion all at once. Sensitized emulsion will last on the shelf for about three months, but most printers usually use up a gallon long before that.