Part IIJ 
Pearson: Antiseptic Treatment of Timber. 
45 
Description of the Process. 
The process of Powellizing timber is not dissimilar to that of all 
other Open Tank methods, though the artificial drying process is in this 
case added to the business. 
The timber to be treated is run into a tank of suitable size, the tank 
being fitted with a door on one side and the loaded trucks run into the 
chamber on a system of tram-lines. On the tank being filled with 
timber, the entrance is closed and the saccharine solution in a cold state 
run in, until the wood is completely immersed by the liquid. The 
solution is then gradually heated to boiling point by a system of heating 
pipes and maintained at that temperature for a few hours, the period of 
immersion at this temperature varying according to the dimensions and 
class of the timber to be impregnated. The solution is then allowed to 
cool down, after which the liquid is run off and the wood removed to the 
drying chambers. It is then subjected to a process of artificial drying, 
which is effected by gradually raising the temperature in the drying 
chamber until sufficient desiccation has taken place, after which the 
timber is removed and said to be ready for use. The temperature to 
which the air is at first raised is stated by the Company to be 130°— 
140° P. and the humidity 85—90 per cent. ; the temperature is gradual¬ 
ly increased until it reaches 165°—170° F. with a humidity of 35 per 
cent, towards the end of the drying process. The time required to dry 
the wood depends on the class and dimensions of the timber to be 
treated; as an instance, it may be stated that a 1 inch piece takes three- 
fourths of a day. 
Theory on which the Process is based. 
The process, as above described, resembles many of the Open Tank 
methods now in use with other antiseptic solutions. The theory, which 
has been expounded on page 38, as to a vacuum existing in 
seasoned wood does not hold good for this process as the timber to be 
treated may be green. On the other hand, the theory that a vacuum is 
formed in the cellular spaces of the timber by the expansion of air on 
heating, does apply to this process. The necessary conditions of an 
Open Tank treatment are further fulfilled by keeping the timber to be 
treated in the solution until it has cooled down, thus allowing it time to 
( U8 ) 
