CONVERSION AND PRESERVATION OF TIMBER 321 





to shrink, actually causes it to split because the cleat will not give way 

 (Fig. e). Thus a plank 20 inches 

 wide which may shrink one inch 

 when dry will perforce have a 

 split in it to the same extent. 



All kinds of timber until pro- 

 perly seasoned, and even some- 



r, J Fig. e. — Wooden cleat, seasoned and split. 



times afterwards, are very sen- ' 



sitive to climatic conditions, and rapidly record every change which 

 occurs. Care should therefore be taken to choose a position where the 

 timber will not be exposed to rain or sunshine, to continual damp, or to 

 cold and dry winds. During the earlier stages of seasoning any of these 

 conditions will damage the wood to a very considerable extent. 



The time required to season timber properly varies so greatly 

 according to the different kinds and sizes and the position in which they 

 are placed, that it is almost impossible to lay down any general rule. 

 A very rough manner of reckoning has been general, which allows one 

 year for each inch of thickness, but this is not reliable. The table given 

 by Laslett, previously quoted, can only be accepted as a rough estimate 

 for large sizes. It is necessary, therefore, to consider each case separately, 

 and examine every parcel by itself. If high-class work is desired it will 

 probably be found necessary to subject the timber to a process of artificial 

 seasoning. This important question is, however, fully dealt with else- 

 where (see p. 385). 



It may be interesting here to mention that before the war many 

 very successful works were completed in mahogany, Japanese oak, and 

 other hardwoods, in which artificially seasoned wood was used. In the 

 case of the oak, the entire work of a very handsome building was com- 

 pleted by the use of fresh logs, sawn, dried, and made into panelling 

 in less than three months from the date of the arrival of the steamer with 

 the cargo. This, after nine years (1919), shows no trace of any shrinkage 

 or other fault, and the expert who has seen it finds it difficult to believe 

 that such a result could be obtained. 



A system was invented by Mr. H. J. Powell which is known as 

 Powellising ; this consists of boiling the timber in a saccharine solution 

 without pressure. It is claimed for this process that, besides being a 

 preservative one, preventing dry rot, and rendering the timber termite- 

 proof, it improves the texture of the wood, which is completely seasoned 

 in a very short space of time. Mr. Walter Birch of High Wycombe has 

 certainly accomplished some remarkable results. For instance, four 

 pieces of English oak were cut from the branches of a tree into a thick- 

 ness of 1 1 inches. These branches from the green, wet log were sawn 

 out, processed, and jointed in four places in twenty-one days. From 



Y 



