48 
Indian Forest Records. 
[VOL. IX 
CHAPTER V. 
The Moisture Content of Seasoned Timber and the Time Required 
for Seasoning according to the Climatic Conditions of Different 
Divisions.* 
The investigation was not planned to give definite data as to the 
actual moisture content of timber which is in equilibrium with the 
climatic conditions of the various Divisions, nor to show the exact rate 
of seasoning of each species. These points are of such importance, 
however, in planning any seasoning scheme or in any attempts to 
ensure complete seasoning of timber before it is put to use, that an 
effort is made to set forth in this report the meagi’e data that are 
available and to go as far as possible in drawing conclusions that may 
be of practical use for guidance until more reliable and definite data 
can be accumulated. 
Wood, like any other substance composed wholly or largely of 
‘cellulose, is hygroscopic and absorbs and gives off moisture according 
to the demands of the atmosphere that surrounds it. .Tests made at 
the United States Forest Products Laboratory show that the hygros- 
copicity of all wood substance is quite uniform in that, when exposed 
indefinitely to a constant relative •humidity at a given temperature, 
all wood substance regardless of the species will come to the same 
moisture content. From these tests curves have been drawn to show 
the moisture content of wood which is in absolute equilibrium \\dth 
various atmospheric constants. Data of this kind based on laboratory 
tests are helpful as far as they go, but they do not supply an answer 
to the question as to the moisture content of seasoned timber in 
various climates, because the actual atmospheric conditions of any 
locality are not constant and uniform, particularly in most parts of 
India. The required data must be accumulated almost entirely from 
field investigation in the various localities. 
In regions having an equable or oceanic climate the problem is 
greatly simplified. In regions characterized by marked seasonal 
fluctuations in the humidity of the atmosphere the soft, porous woods 
in small dimensions react very quickly to changes in atmospheric 
conditions so that they tend to go through the extreme range — from 
the maximum moisture content of the wet season to the minimum 
moisture content of the dry season. The more dense the wood and 
the larger the dimensions into which it is cut the slower the change in 
moisture content, so that it often happens that before a piece of timber 
has had sufficient time to come into equilibrium with one extreme. 
* Note — It is hoped that in a short time sufficient data will be available to permit 
the revision of this Chapter so as to give more reliable and dednite 
information regarding this veiy important phase of the subject of 
seasoning. 
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