Differences Between Joint Compounds for a Drywall

All-Purpose Compound

• All-purpose compound is suitable for all taping applications, making this mud the only type that’s needed to finish out most walls. You may apply it as a base coat and as a top coat. It sands well but not quite as well as topping compound, and it dries a bit slower than a fast-setting mud or a basic setting compound. All-purpose compound is the best choice for most do-it-yourselfers because it allows the taper ample time to smooth out the mud before it sets.

Setting Compound

• Setting compound sells in powdered form only, because it begins to set soon after you mix it with water. Setting compound dries quickly but doesn’t sand as easily as all-purpose compound or topping compound. Professional drywall contractors often use setting compound because they can apply multiple coats in a single day. But unless you’re a skilled taper, an all-purpose compound will be easier to work with.

Topping Compound

• Topping compound is intended for use on the second and subsequent applications but not on the first. This type of compound comes premixed, so there’s no need to worry about blending away lumps, and it has a fine texture that is simple to sand with a drywall-sanding screen. Topping compound is lightweight and spreads smoothly.

Fast-Setting Compound

• Also known as “hot mud,” fast-setting compound sells in premixed or powdered forms, and the package label indicates the average time, in minutes, that is required for drying. Hot mud relies upon air-drying and a chemical reaction to speed setting times. It’s easier to sand than setting compound but not as easy to sand as topping compound. Between applications, drywall taping knives and pans must be thoroughly cleaned, because a small bit of dried compound can make a fresh batch of hot mud set within a few minutes.