When using a diazo-sensitized emulsion, how do I know if I have it mixed properly?
Use warm distilled water. Warm water dissolves diazo—especially powdered diazo—more effectively than cold water and distilled water eliminates the possibility of impurities that can react emulsion pre-maturely. Stir the emulsion slowly but thoroughly and double check the mixed emulsion in white light momentarily to make sure no yellow is present. Yellow safelights mask yellow diazo making it hard to see if emulsion is mixed properly. Don’t worry, white light will not crosslink emulsion in such a short period because there is so much water present in the bucket. Give the mixed emulsion ample time (usually a couple of hours) to let the air bubbles escape before using.
Article Origin: Printwear