Drying timber degrade

The appearance of the timber in the dried wooden vessel is not perfect, and some longitudinal and transverse cracking has appeared. This result raises the question of the need for pretreatment to alleviate the considerable stresses involved in direct freeze-drying of degraded wet wood. The system used to treat the Marseille wreck was nevertheless conceived on an imaginative scale and deserves further research and development, particularly with respect to appropriate pretreatment. 

If the timber is prone to degrade due to too rapid drying the thickness of the stickers can be redueed, to say 15 mm, to reduce the airflow through the stack. Stacks can be moved eloser together and stored at the leeward side of the yard. To further inhibit airflow, staeks ean be eovered with horticultural shade-cloth (50% open mesh), but the boards will need to have had an anti-sapstain treatment. 

Some success has been reported with hardwoods, but only for those species that are not particularly difficult to dry using conventional schedules. Overall drying time can be halved but at the expense of additional degrade such as honeycombing and collapse. Some recalcitrant timbers may be dried successfully but only if they have been pre-dried to the fibre saturation point. Other hardwoods cannot be high-temperature dried at all. 

Moisture Content. In a specific circumstance (a treatment problem of a group of oak timbers), the moisture content and the amount of internal sound wood core were used instead of chemical analyses to assess degradation (6). The wood condition has been classified as follows Class I, the most deteriorated wood, contains over 400% water ([weight of water] / [oven-dry weight of wood] X 100) and virtually no core Class II is 185-400% water, with a core present and Class III is less than 185% water, with only the surface degraded. The analyses included moisture contents and the pin test to determine the extent of sound wood. 

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