Acid Yellow 7 is a dye solution in a water/acetic acid/ethanol mixture that is used for staining fingerprints and shoeprints made in blood. Prints in blood are colored yellow after treatment with Acid Yellow 7.They then fluoresce under blue/blue-green light.Acid Yellow 7 should not be used on absorbent surfaces like paper, carton material, bed sheets, or carpet. It works very well on non-absorbent backgrounds like linoleum, glass, tiles, painted surfaces, or PVC floor covering. Before staining, prints in blood should be fixed to prevent them from running (causing loss of detail) when the staining solution is applied. In general fixative is applied before any staining solution except Leuco Crystal Violet, which contains fixative