Dry kiln and method

A process for accelerating the drying of a wood piece having an exterior surface and an interior comprising the steps of

• heating the wood piece in a chamber to a selected temperature,
• reducing the pressure in the chamber while heating the wood piece by conduction with a flexible heating means which conformably engages the surface of the wood piece to establish a vapor pressure gradient in the wood piece sufficient to cause water vapor in the interior of the wood piece to move toward the exterior surface of the wood piece, the heating means being sufficiently flexible for remaining in contact with the surface of the wood piece substantially throughout the drying process.

A device for accelerating the drying of a wood piece having an exterior surface comprising

• a housing having a chamber into which the wood piece can be placed,
• a flexible heating blanket for heating the wood piece by conduction, and vacuum means for reducing pressure in the chamber, the flexible heating blanket being sufficiently flexible to conform to the exterior surface of the wood piece substantially throughout the drying of the wood piece.

A kiln comprising a sealable container into which a charge of wood arranged in a plurality of vertically stacked layers of planks may be placed, means for heating the planks, said heating means including a plurality of thin flexible heating blankets disposed respectively between the layers of planks and conforming to the surfaces of the planks, means for pulling a vacuum within said container and means for condensing water vapor driven from the planks by the combined effect of heating them in a reduced atmosphere, said condensing means being disposed within said container.

A process for conditioning wood to reduce case hardening of the wood at the end of the drying process in a chamber comprising the steps of

• removing the majority of the moisture from the wood,
• heating the wood in the chamber at subatmospheric pressures to allow additional moisture to migrate from the wood core outwardly to the wood surface,
• promoting recondensation of moisture vapor at the wood surface, to wet the surface of the wood to release tension and case hardening of the wood surface.

A device for accelerating the drying of a plurality of layers of wood pieces, comprising a housing having a chamber into which the wood pieces can be placed, flexible heating blanket for heating the wood pieces, and vacuum means for reducing pressure in the chamber, the flexible heating blanket being sufficiently flexible to permit it to be disposed in serpentine relation about the layers of wood pieces.