The Wisconsin Department of Natural Resources (DNR) Forest Products Services recently worked with UW-Extension and the Department of Agriculture Forest Products Lab to develop a technical primer highlighting vacuum drying technologies for lumber manufacturing.

This research was completed by using the vacuum kiln at Northcentral Technical College. Vacuum drying technology has recently gained attention in Wisconsin because of the availability of lower-cost vacuum kilns for smaller wood product manufacturers.

Vacuum drying utilizes a pressure vessel, a heat source and a vacuum pump to control the drying conditions under less-than-atmospheric pressure. This process is an economical alternative to conventional drying for many species under various environmental and economic conditions.

Vacuum drying can reduce drying time and be more energy-efficient than conventional steam drying. However, there are many factors to consider when comparing the two technologies. Ideal applications for vacuum kilns include high-value wood species, difficult-to-dry species (e.g. oak), timbers, large sections of logs and lumber (including live-edge slabs and wooden rounds), decorative or thick veneer and small-scale woodworking operations.

The new report describes the principles and practices of vacuum drying and discusses its advantages and disadvantages. To learn more about this technology and drying lumber, please view the recent technical report by visiting this webpage.