NOTES ON CREOSOTING. 1 7 7 



the air remaining in the cells of the wood, and this causes 

 a lowering of pressure in the cells, which again forces 

 more creosote into the wood to fill the partial vacuum so 

 produced. 



The initial cost of a small creosoting plant of the type 

 described above, with a boiler say 20 feet long, 4 ft. 6 ins. wide, 

 and of the same depth, would be about £60. 



3. The third and simplest method is that of simple immersion. 

 This means simply soaking the timber in cold creosote contained 

 in a suitable tank. An old boiler answers very well indeed, 

 and is cheap. In this case very dry timber and thin oil are 

 essential. The method has much to recommend it in the case 

 of small estates, where the operation can be attended to at 

 intervals by an odd man. 



The question as to which of the three methods described is 

 the best is a difficult one. It may, however, be said that under 

 special circumstances all are quite successful. At present 

 considerable confidence in both the pressure and boiling 

 methods prevail, among those specially concerned with the 

 matter, but the method by simple immersion is as a rule less 

 favourably regarded. This is unfortunate, for in dealing with 

 inferior timber on small estates, or with similar timber in the 

 out-lying portions of large estates, creosoting can only be profit- 

 ably carried on with a cheap form of plant. The great obstacles 

 to the impregnation of timber with creosote are the air and the 

 moisture in it. In the pressure and boiling methods, the method 

 itself includes means for getting rid of the air, and the moisture 

 should be got rid of by preliminary drying. In the method by 

 simple immersion, the air is got rid of by prolonged soaking, and 

 I he process is probably accelerated if the timber is placed at an 

 angle of 30° or so in the tank. 



With a view to investigating the value of the last method, 

 the author carried out an experiment, the results of which are 

 given below. 



In this experiment pieces of timber creosoted by the pressure 

 method (pressure employed 90 lbs. to sq. inch) and by the 

 immersion method (the period of immersion being one week) 

 were alike plunged in water for fourteen days. To ensure 

 uniformity each log of timber was split into two, half being 

 treated by immersion and half by pressure. The table shows 

 the results : — 



