Skinning

[1] The formation of a film on a thick paint layer before the solvents in the layer under it have evaporated
[2] When adhesives and sealers contain fast drying solvents, there is a tendency for the applied film to dry rapidly at the surface which slows down the evaporation of the solvent that remains in the film. This condition can lead to blistering, checking or cracking, particularly if the film is exposed to temps near or above the boiling point of the solvent.
[3] Many coatings, particularly oxidizing types, have a tendency to skin over when left exposed to the air in an open vessel or in a partially filled container. Later when the material is forced through a spray gun, the air breaks the skin into a number of particles which appear on the work as specks. This condition can be overcome by straining the coating and by taking care to store it in completely filled containers.