THE ARTIFICIAL SEASONING OF TIMBER 387 



During the period of the war, conditions altered materially. On 

 account of the shortage of shipping space for timber, all existing stocks 

 of seasoned and partly seasoned wood were drawn upon without replace- 

 ment, and thus a time arrived when the timbers most needed, namely, 

 those used for munitions and aircraft, were practically unobtainable in 

 a seasoned state. The continued prejudice against artificial seasoning, 

 and the lack of official sanction of it, caused enormous quantities of 

 finished parts to be made up of unseasoned timber. These were naturally 

 unsatisfactory, and were either rejected on inspection or, in cases where 

 shrinkage did not develop until later, further damage to material and 

 even danger to life occurred. 



The question was finally taken in hand, and the War Office issued a 

 permit for artificial seasoning under certain specified conditions, namely : 



1. That the particular process be approved. 



2. That the drying be carried out under supervision. 



As the situation with regard to aircraft timber was most serious 

 and production was being affected, the Air Board took immediate 

 advantage of this concession and estabHshed the necessary technical 

 organisation for testing the results from the various systems of timber 

 drying, together with the staff for super\nsing the approved plant. A 

 census was made of all existing timber dryers of all types in the country, 

 and those most suitable for aircraft timbers were taken over. A large 

 Compartment Sturtevant Dryer belonging to Messrs. W. W. Howard 

 Brothers & Co. at Poplar was used for establishing data, and also as a 

 training school for kiln supervisors and operators. An Erith progressive 

 dryer was then taken to ascertain the results obtainable with that method. 

 Instruments for keeping autographic records of temperature and humidity 

 were installed in all the dryers in order to keep an exact record of the 

 conditions undergone by each separate charge of timber, and these were 

 kept, together with the tests made on the timber both before and after 

 drying. Having ascertained the exact conditions of time, temperature, 

 and humidity necessary for various kinds and thicknesses of wood, and 

 having trained men to operate the various dryers, a process was arranged 

 which secured homogeneity of result for all timbers used in aircraft 

 manufacture. It is noteworthy that far from any concession as to 

 strength and elasticity being required for timber artificially seasoned 

 under proper conditions, the standards set for naturally seasoned wood 

 were passed, and in most cases with a considerable margin. 



It is clear, therefore, that artificially seasoned timber has been used 

 with, success in a manufacture which subjects it to the most severe tests, 

 viz. the manufacture of aircraft, but it is important to recognise that 

 the process, to be successful, must be scientifically carried out in properly 

 equipped dryers by trained men. 



