putty, commonly a mixture of whiting (calcium carbonate) and boiled linseed oil. Other substances may be combined with the oil to make putties suitable for some specific purpose. For example, the red and white oxides of lead mixed with linseed oil form a putty used in sealing pipe joints. Putty hardens gradually when put in place, as along the edges of window panes to fasten them, in cracks in plaster walls, and in crevices in wood and other substances. The linseed oil absorbs oxygen from the air and, holding fast the calcium carbonate or metallic oxides, causes the mixture to harden. A powder composed of a mixture of lead and tin oxides, known as putty powder, is extensively used in polishing. Putty is generally being replaced in many applications by caulking materials of butyl and silicone rubbers. The higher cost of these materials is offset by their greater durability.