Cement for making joints in hot-water pipes contains 80 to 100 parts, by weight, of iron borings (which must be pounded if coarse), 2 parts of flour sulphur, and 1 part of powdered sal-ammoniac. The ingredients must be well mixed and moistened with water, this being done from half an hour to two hours before use, according to the weather. The joint is first caulked a little more than half full of yarn, then finished with the prepared borings. The borings must be caulked in carefully, or the socket will be split as the joint sets, for the borings expand a little in setting.