Dual Cure Diazo emulsions need to be mixed before use. The diazo is the light sensitive agent mixed into the emulsion to activate it. Once mixed, these emulsions have a shelf life of two to three months.
Pre-sensitized emulsions are ready to use.
Typically these emulsions will expose much faster than the dual diazo emulsions, they also have a longer shelf life. The drawback to a fast exposure is the exposure latitude, this is the level of forgiveness that the printer has for over/under exposure. Presensitized emulsions have a very short window or latitude to expose within. We recommend using dual cure emulsions, which expose longer, but have a much wider exposure latitude and level of forgiveness.
When doing signs you will need an emulsion that will stand up the harsh solvents and cleaners used in the process. They are offered as dual diazo and pre-sensitized formats however they are much tougher and can withstand the washout with chemicals or water, which may otherwise cause the screen to breakdown prematurely.