DAP 7079812290 Elastopatch Textured 02 Gal Raw Building Material, Gallon, Off- White, 128 Fl Oz

Has mine gone bad? There's about an inch of water on top of the compound with a lot of black flecks floating in water. Almost looks like mold

Is this brush grade or knife grade?

Has mine expired or gone bad? There' about an inch of water on top of the compound with a lot of black flecks floating in water. Almost looks like mol

What subsurfaces are acceptable for ideal adhesion? I'm thinking of using it on a closed-cell foam with a mesh underlayment.