Quality wooden furniture requires timber seasoned to the highest standards. To achieve this goal and reduce operating costs many designer/makers are drying their own material.
The most practical technologies for drying smaller quantities of lumber are solar and dehumidification. Solar technology has low operating costs but requires high standards of insulation/construction to operate successfully in Canada. Dehumidification technology uses a compressor operating on expensive electrical energy but can often dry to faster schedules than solar technology, especially in winter.
No matter which drying technology is chosen it is important to understand that the final moisture content of your wood is directly related to the humidity and temperature of the surrounding air. The equilibrium moisture content (EMC) of the wood in your workshop can be determined using this on-line calculator.
Johnathan Guest, a designer/maker with a studio in Wales, has a Web site with a detailed "slide show" of the operation of his solar kiln. The plans for a small kiln using domestic dehumidifying units were made available to VCR by Bruce Williamson of Oyster River Tone Woods.
Jim Birkemeier of Timbergreen Forestry in Spring Green, WI, sells plans for solar kilns with capacities of 14,000 to 100,000 board feet per year.
Designer/makers with limited knowledge of timber drying should start by reading Understanding Wood and Identifying Wood
by R. Bruce Hoadley. Also
Fine Woodworking on Wood and How to Dry It,
Selecting and Drying Wood and the links in the sidebar.
Portable Moisture Meters
Monitoring the moisture content (MC) of your wood at major stages in the furniture production process is essential for quality control. You can us either a pin-type (resistance) meter or a pinless-type (dielectric) meter. Though many older texts claim greater accuracy for the pin-type meter, a 1997 study (*) found both models to be equally accurate when the pinless meter is calibrated for the density of the tested species.
Larry Osborn, Research Associate of Wood Technology and Anatomy, Appalachian Hardwood Center, West Virginia University, favours the pinless meter for furniture producers. He commented that the pinless meter can be used to "quickly measure MC at more than one position on a piece of wood, without concern for damaging the wood with a myriad of pinholes. Multiple measurements give a better estimate of the MC over the whole piece, or over more pieces in a stack, than will single measurements taken in locations where the primary concerns are operator convenience, or hiding the damage caused by the pins (for example at the ends and edges of boards) and where the MC measurements may therefore be less representative of the MC for the whole board."
(*) Evaluation of Electric Moisture Meters on Kiln-dried Lumber by Gene Wengert and Paul Bois, Forest Products Journal, Vol. 47/6