What is drywall joint compound, or “mud”?
Drywall compound is a water-based paste that is used to cover seams, holes and make repairs in walls, ceilings and, in some cases, even painted woodwork! It is available premixed in containers up to 5 gal., or as a powder that is mixed with water. It is a combination of some or all of the following materials: limestone, dolomite, water, perlite, vinyl polymers and crystalline silica. The combination of these materials gives drywall compound good adhesive properties, limited flexibility, and a hard, smooth surface for painting. When primed and painted, it is almost indistinguishable from the drywall it has been spread on! Prior to 1980, many joint compound formulations contained asbestos, which is a known carcinogen under some conditions and for some people. Though modern compounds contain no asbestos, care should be taken when doing repairs that might raise dust in older buildings.
