Skin sealants are applied over skin preps to seal the skin and hold any remaining bacteria in place prior to incisions. It is desirable for the person applying the sealant to know where the sealant has been applied. It is also desirable to be able so see through the sealant to observe the skin to detect any possible infection. A skin sealant is provided that has a pH indicator and co-additive acid that react soon after mixing, rendering the skin prep colorless.