Sharp sand under air pressure is used in etching or frosting glass and cleaning castings. The pressure of the air and hardness of the sand is governed by the class of work.

A sand blast outfit includes a sand blast machine, hose and nozzles, and a standard air compressor of the size and pressure capacity required by the conditions of the work, together with a good-sized air receiver with the usual gauges, safety valves, and drain cocks. If air is already in use at the location, at higher pressures than required for the sand blast operation, a pressure reducing valve may be installed, leading preferably to a separate receiver which will be maintained at the proper pressure for the sand blast operation.

A clean, sharp sand, thoroughly dried, will give best results, and it is essential that the air used with the blast be kept as dry as possible by the installation of blow-off cocks, and occasionally "U" loops introduced in the line of air piping, with drip cocks installed at the bottom of the loops; or by the ordinary bucket steam trap. Sand especially suited to the operation can be obtained from manufacturers of the sand blast machines.

For etching on, or frosting glass, a pressure of 2 to 5 lbs. is ample; for cleaning brass castings and removing core sand, 15 to 20 lbs.; for cleaning the general run of iron castings, 15 to 20 lbs.; and for steel castings, 30 to 75 lbs.