Calcium sulphydrate can be made by heating a granulated mixture of plaster-of-paris (calcium sulphate) with granulated wood charcoal (to take off the oxygen). A high temperature is necessary and it is best obtained by means of gas. A muffler is used, i.e., set in cinders or bone ash and the mixture is heated to redness.
By this method neither sulphuric acid or sulphid of iron is used. The dry, rose-colored or whitish product is applied to the skin in a wetted condition, or it may be put on dry and then wetted. Hydrogen sulphid is given off, which causes a rather foul smell. The substance is perfectly harmless to the skin and may be left on any length of time and does not even irritate abraded surfaces. It is not patented and can be made cheaply.