[Pboc. Roy. Soc. Victoria, 35 (N.S.), Pt. I., U)^2]. 



Akt. V. — On Ihe Drying of Timber, 



By REUBEN T. PATTON, B.Sc, M,.F. 



(With 9 Text Figures.) 

 [Read 8th June, 1922.] 



The drying of timber is governed by six factors, namely, Moisture 

 Content, Diffusion cf Moisture, Evaporating Surface, Thickness, Hum- 

 idity and Temperature. Tlie first two may be conveniently referred 

 to as the biological factors since they are due to the plant's activity, 

 and are quite beyond our control. The last two may be referred to as 

 the mechanical factors, since we can vary them at will. The two inter- 

 mediate factors, Evaporating Suriace and Thickness, belong partly to 

 both. We may cut a piece of timber to any thickness, or so as to 

 expose more cr less of one face than another, but having so cut it, its 

 drying will be governed by the organization of the wood substance. 



The work contained herein was commenced at Melbourne (Vic- 

 toria) and was subsequently carried on at London. The work had its 

 origin in the difference of opinion which exists as to the relative 

 merits of air and kiln-drying of timber. The research had for its 

 C'bject a study of all the factors influencing the drying of timber, in 

 order to ascertain what is involved in the phenomenon of seasoning. 

 It may be here remarked that the term kiln seasoning involves widely 

 different ideas and practices. In some kilns, wholly artificial condi- 

 tions are used, the temperatures used, for instance, being far in excess 

 of any found in nature. On the other hand, some kiln drying is 

 carried on at about the maximum atmospheric temperatures. In this 

 latter case, it is the continuance of the temperature, not the tem- 

 perature itself, that is artificial. Timber in our State may be subject 

 to- a temperature of 123. 5F, and at Melbourne itself to a temperature 

 of llloF. 



There is no doubt in the mind of the wood worker as to the value 

 of air-seasoned timber. Up to the present generation, all the finest 

 wood work of the world has been carried out with air-seasoned timber. 

 That is, in itself, quite a sufficient answer to the statements some- 

 times made that air-dried timber is inferior to kiln dried. However, 

 modern civilisation demands a greater supply of seasoned timber than 

 can be met by the old practice of air drying. The first aim, therefore, 

 was a study of drying under conditions which have produced such sat- 

 isfactory results in the past. The work, therefore, was carried on at 

 such temperatures and humidities which, with slight exceptions, are 

 found in nature. 



Moisture Content. — In the seasoning of timber we are concerned 

 not only with how much moisture there may be in the wood of a tree 

 when it is felled, but also how that moisture is distributed in the 

 tree, and also whether the moisture content is a constant all through 



