The oilstones in most general use are four in number - the Turkey, Washita, Charnley Forest, and Arkansas. The Turkey stone is known as white, grey, or black, but generally its colour is a mixture of brown and blue shades. It is a close-grained stone, and, though not used for very fine edges, it cuts quickly and is suitable for ordinary use. It wears away rather irregularly. The Washita (Ouachita) stone is yellowish-grey in colour, and though it wears away quickly it does so much more regularly than Turkey stone. The Charnley Forest stone is of a greenish-slate colour with sometimes small brown or red spots. The lighter the colour of the stone the more serviceable it will be. Arkansas oilstone is a compact white stone resembling Washita stone, but it has a finer grain. It wears well and cuts slowly, being largely used for finishing the edges of surgical instruments. The stone should be cemented into the box made to receive it, not with white lead, but with a mixture of hot glue and dry red lead. White lead is taken up by the oil used with the stone and tends to harden its surface. When an oilstone has been in use for some time its surface is apt to become hard, especially if certain oils are used with it.

The reason is that the pores of the stone are closed by the viscid or gummy oil, which contains particles of steel rubbed off in sharpening; when the stone is in this condition it is not touched by the tool, which rides upon a substance as hard as itself; therefore the stone fails to sharpen the tool. A mixture of oil and turpentine is often applied to hard stones to cause them to cut better; for this purpose, also, they are sometimes boiled in soda water. Hard oilstones may be made to give rough edges to tools by sprinkling a very little Hour emery on them after the oil has been applied. Neat's foot oil is the very best for oilstone use, all others hardening the surface much more quickly. Soap has been recommended for the purpose. The stone is wetted and rubbed with soap and more water is applied until a lather forms. This is allowed to dry, and when the stone is required for use it is merely necessary to wet it slightly. Oils in common use for stones are sperm, olive, and sweet oil; these are often mixed with heavy petroleum. It is sometimes required to cut an oilstone into pieces, and this may he done by rubbing across it the edge of a sheet of soft iron or mild steel, using sand and water as required.

Or, instead, a piece of hoop iron (such as that used on casks) may be used with emery either wet or dry as the cutting agent. Another method is to insert a piece of an old small-toothed hand-saw into a wooden block and to rub the stone on this. The teeth are, of course, set uppermost.