Please don't feed any animals gypsum board(aka drywall/sheetrock). People don't realize what is in this stuff. Especially since these days a lot of it comes from china. Oyster shell is too cheap. I realize there are ways to cut corners to save money but feeding animals building materials full of chemicals is not one of them. Remember a while back where people were getting sick in their own homes due to improperly manufactured drywall.
http://en.wikipedia.org/wiki/Drywall
Manufacture
A wallboard panel is made of a paper liner wrapped around an inner core made primarily from gypsum plaster, the semi-hydrous form of calcium sulfate (CaSO4·½ H2O). The raw gypsum, CaSO4·2 H2O, (mined or obtained from flue gas desulfurization (FGD)) must be calcined before use. Kettle or Flash calciners typically use natural gas today. The plaster is mixed with fiber (typically paper and/or fiberglass), plasticizer, foaming agent, finely ground gypsum crystal as an accelerator, EDTA, starch or other chelate as a retarder, various additives that increase mildew and fire resistance (fiberglass or vermiculite), wax emulsion for lower water absorption and water. This is then formed by sandwiching a core of wet gypsum between two sheets of heavy paper or fiberglass mats. When the core sets and is dried in a large drying chamber. The sandwich becomes rigid and strong enough for use as a building material. [3].
http://en.wikipedia.org/wiki/Drywall
Manufacture
A wallboard panel is made of a paper liner wrapped around an inner core made primarily from gypsum plaster, the semi-hydrous form of calcium sulfate (CaSO4·½ H2O). The raw gypsum, CaSO4·2 H2O, (mined or obtained from flue gas desulfurization (FGD)) must be calcined before use. Kettle or Flash calciners typically use natural gas today. The plaster is mixed with fiber (typically paper and/or fiberglass), plasticizer, foaming agent, finely ground gypsum crystal as an accelerator, EDTA, starch or other chelate as a retarder, various additives that increase mildew and fire resistance (fiberglass or vermiculite), wax emulsion for lower water absorption and water. This is then formed by sandwiching a core of wet gypsum between two sheets of heavy paper or fiberglass mats. When the core sets and is dried in a large drying chamber. The sandwich becomes rigid and strong enough for use as a building material. [3].
Last edited: