IMPREGNATION 



183 



2. The Loivry process. Air-seasoned timber, of the same species, density, and moisture contents, 

 is laid on tram-cars and placed within the retort cylinder. The cylinder is then filled from the 

 charging tank with creosote oil at a temperature not to exceed 200 degrees Fahrenheit. The 

 main line is then closed and oil from the charging tank is forced, by pressure pumps, into 

 the retort until the timber has taken oil to the point of refusal, or a predetermined amount. The 

 pressure within the retort is controlled so as to give a maximum penetration of the oil. There- 

 upon, pressure is released and the free oil in the retort is drained off. A vacuum of sufficient 

 degree and duration is then drawn in the retort so as to recover that portion of the free oil in 

 the timber which exceeds the specified amount. The recovered oil is drained off from the retort 

 and the charge is withdrawn. 



3. The Rueping process. The timber to be treated should, preferably, be thoroughly air-seasoned. 

 Green or partially seasoned timber must be steam-dried before treatment. The timber is subjected 

 within the steel cylinder to an initial air or gas pressure. In most cases, this compressed air 

 is introduced direct from the compressor. The wood must be exposed to the full influence of 

 the compressed air for a sufficient time to thoroughly fill all the cells and cavities of the wood 

 with such compressed air. During the next step of the operation, in proportion to the quantity 

 of impregnating liquid admitted into the cylinder, air is allowed to escape in order to make room 

 for the required quantity of liquid. 



This next step consists of the introduction of the impregnating liquid (creosote oil), under a 

 still higher pressure, into the treating cylinder. Sufficient liquid must be introduced to completely 

 fill the cylinder. The air escape valve must be at the highest point of the cylinder to avoid air 

 pockets forming in the liquid. 



When the material in the cylinder is completely covered with the liquid, the pressure is 

 raised slowly, step by step, by introducing additional quantities of impregnating liquid until the 

 pressure has reached the desired maximum securing a full penetration of the cells of the wood. 

 The maximum pressure must be maintained until the timber will not absorb any more of 

 the liquid. 



Interior of a retort house, American Creosote Co., SeaUle, Washington. 



