Collapse
Collapse is a form of degrade which is liable to occur with certain timbers.
Some species of eucalyptus and coconutwood, for example, are particularly prone
to this form of degrade which can develop at moderate as well as high kiln
temperatures. Collapse occurs during the early stages of drying when the free
moisture leaves the cells, and is caused by the surface tension which develops
as the amount of water in the cells decreases. This causes the cell walls to be
pulled inwards and to collapse. Rapid drying at high temperatures when the cells
are more plastic may cause a large proportion of the cells to collapse. Local
shrinkages may become large and collapse may frequently be accompanied by severe
honeycombing.
ln many instances, much of the collapse and consequent distortion may be
removed when the wood is nearly dry by means of a high temperature/high relative
humidity treatment, referred to as reconditioning.
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