A good insulating material for electrical conduits is made by the mixture of 34 parts finely pulverized resin with 66 parts fine glass or quartz powder. To this compound the addition is to be made of 26 parts of either beeswax, spermaceti or paraffine and 36 parts of either crude or boiled linseed oil. The proportions of the various ingredients should be in accordance with circumstances. If the compound is intended for exposure to the sun, the amount of wax used should be small; while the converse is true should the compound be employed for underground lines. Another insulating material for electrical conduits is made by constantly stirring in a boiler, at a heat between 92 degrees and 212 degrees Fahrenheit, 29 parts Wood Tar, 36 parts Shellac, 32 parts Asbestos, 1 part Mineral Wax.
Should this compound be insufficiently hard, a smaller quantity of wood tar can be used. If a mass of extraordinary hardness is desired, the amount of asbestos used can be decreased and wax can be omitted and about 24 parts of infusorial earth clay, without any traces of iron in it, or ground slate, can be used.