Creosoting. The apparatus employed consists of one or more heavy metallic cylinders having end doors which open to the full size of the cross-section of the cylinder, and which are made to close steam-tight. A track extends through the cylinder, upon which runs a truck or car carrying the material to be treated. Pumps and other accessory apparatus are in pipe connection with the cylinder.

The timber to be treated is loaded on a truck and run into the cylinder, after which the doors are securely closed. Steam under considerable pressure is then admitted to the cylinder, and this heats the timber and supplies moisture to fill the pores of the wood and pressure to force it in, thus augmenting its porosity. This accomplished, the steam is shut off and a vacuum pump is employed to reduce the pressure within the cylinder to as low a point as possible, with the result that the moisture forced into the wood, having served its purpose in opening the pores, is now drawn out. The liquid creosote is then introduced into the cylinder and under an increase of pressure the timber expands and the liquid penetrates far beyond the surface of the material. Pieces which are not more than eight or ten inches across are penetrated to their center.

After the pressure is withdrawn, the surplus liquid is drawn off, the doors are opened, and the wood is removed. The process as described is subject to several modifications.

It is usually unnecessary to treat wood which is designed for the interior of buildings, the process being chiefly valuable for such materials as come in contact with the ground or are used about the water.