302 THE UTILISATION OF WOODLAND PRODUCE. 



105 is usually sufficient. The damper the wood, the slower 

 should the rate of seasoning be, as rapid heating makes the 

 planks warp and split. There should not be too much ventila- 

 tion; it is sufficient if the air be renewed once every five 

 minutes. But this depends mainly on the dampness of the air, 

 as in very dry air the evaporation of the sap proceeds so quickly 

 that the wood may easily become split and cracked. After 

 drying, the wood should still contain about 10 to 12 per cent of 

 water, for if thoroughly dried it is brittle, difficult to work, 

 absorbs moisture rapidly, and is then apt to warp. The time 

 taken to season wood depends on the kind, and on its shape, 

 size, and moistness. For thin boards and planks about 3 to 5 

 days suffice, while from 8 to 10 are needed for larger wood. 

 Another method is Haskin's Vulcanisation process of rapidly 

 seasoning converted timber by hermetically sealing it in power- 

 ful iron cylinders and exposing it under a pressure of about 13 J 

 atmospheres (200 Ibs. per square inch) to the influence of air 

 (dry?) superheated to between 200 to 300 Fahr., the precise 

 temperature being the secret of the process (probably a little 

 over boiling-point, 212). The time taken depends on the size 

 of the timber ; for sleepers 8 hours suffice. 



In steaming, the converted timber is usually put into a thick 

 wooden box 10 to 12 ft. long and 5 to 7 ft. broad and high, 

 bound with iron and hermetically closed, the box resting 

 slantingly on strong supports, so that the condensed water can 

 be run off at the lowest part by a turncock, while the mouth of 

 the steam-pipe enters at the opposite end. To economise steam, 

 the wood is packed closely into the box, but the boards are set 

 on edge so that their surfaces should come into contact as little 

 as possible. When steaming is begun, the condensed water 

 runs off fairly clear, but later on it gets much discoloured and 

 smells strongly of the extracts dissolved ; but the steaming is 

 continued until the condensed water again runs clear and 

 colourless, showing that the sap has been fully dissolved and 



