184 



IMPREGNATION' 



The pressure is then cut off and the impregnating liquid is discharged from the cylinder. 



It is not necessary to limit, in any way, the final absorption of the timber; in fact, it is better that 

 no limit be placed on it so that, for a certainty, all parts of the timber which will take treatment are 

 reached by the impregnating liquid. 



If it is shown after the end of the run, that the final absorption is too large, then either the initial 

 air pressure may be increased or the liquid pressure decreased. 



If it is shown that the final absorption is too small, the air pressure may be decreased or the liquid 

 pressure may be increased. 



View of the booms of the American Creosote Co., at Creosote, Puget Sound, Washington. 



The final absorption is dependent on the relative differences between the air pressure and the 

 impregnating liquid pressure. By regulating the comparative height of these pressures, the final absorption 

 can be adjusted to the specified or desired quantities. 



The time required for absorption depends on the length of time at which the liquid pressure is 

 maintained at its maximum. 



The last step in the Rueping process -very characteristically -consists in the application within the 

 steel cylinder of a vacuum. The vacuum tends to expand the compressed air within the cavities of the 

 timber. The vacuum is maintained until, in the surface sections at least of the timber, a pressure equal 

 to atmospheric pressure is established. 



The expanding air forces a large amount of creosote oil out of the timber. Indeed, all that creosote 

 oil may be expelled which has failed to incrustate the cell walls and which, as far as the life of the 

 timber is concerned, is injected in vain. 



The timber leaves the cylinder dry. The escape of additional compressed air, taking place during 

 the next hours, should not cause any dripping of creosote from the material thus treated. 



