Vacuum drying is not a new technology, its use for drying wood has been around since the early 1900s, granted much research on this drying method has only been accomplished since the mid-1980s. In vacuum drying, wood is placed in an airtight vessel under less than atmospheric pressure, while heat is transferred to the material using one of several methods.
I will identify three categories basically used in today's environment. Plate vacuum drying, steam vacuum drying, and radio-frequency vacuum drying. What separates vacuum drying from conventional drying is that with vacuum kiln drying, there is greater water migration in the longitudinal direction, which allows you to get the water out quickly.
Other advantages of vacuum drying are: the ability to dry at lower temperatures over traditional conventional drying, which in turn will lead to fewer drying defects, reduced drying times (especially for hardwoods and very large slabs, improved color preservation, higher energy efficiency, little to no loss of volatile organic compound emissions, and the ability to dry very large slabs.
While the past was focused on increasing the level of understanding (education) more recently most efforts have concentrated on improving existing methods, for example by improving moisture control and the use of pretreatments to improve drying quality.
Although vacuum drying has been around for a long time, it has not yet become a mainstream wood-drying method. Its Entry cost is high, it's still limited to high-value lumber, like large slabs and specialty applications. Our belief is that as the need to streamline supply chains and deliver more customized products increases, the market will be compelled to give vacuum kiln drying serious consideration.