Re: what is sheetrock mud made of?
Gypsum wallboard is a slurry of powdered gypsum and water with other additives, which is sandwiched between paper and dried. Premix gypsum "mud" is essentially the same stuff. Most if not all of the water is lost through evaporation as it dries.
Plaster, while it looks similar to gypsum, is a cementitious product. To produce the plaster, limestone must first be baked to remove water (it becomes anhydrous). When mixed with water, it forms a chemical reaction where the water becomes a binding agent (it becomes hydrous), remaining a part of the plaster as it cures and hardens. While some of the water is lost through evaporation, most of it remains in the finished product. Plaster isn't dried like gypsum; rather it is cured.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.