An efficient method for the impregnation of porous materials, particularly of low permeabilities, for the purpose of studying the pore system is described. A brief review of previous methods is given, as well as a description of the proposed method and apparatus.

In brief, the method consists of evacuating the air from a clean, dry specimen at room temperature, immersing it in molten balsam, to which an oil-soluble dye has been added, and then forcing that balsam into the evacuated pores under pressure.

The equipment is very simple and inexpensive. It requires only an air-tight cylinder, a means of evacuating it, a method of later applying pressure within it, and a heating unit which will melt the balsam at the proper time.

The pores, as they appear in the resulting sections, are impregnated with the brilliantly dyed balsam, so that a complete study of their size, shape, number, interconnections, and distribution is possible.