If your antique family rocking chair or your wood dining chairs start to squeak and wobble chances are the humidity in your home is too low. On the other hand, if you notice swelling or warping, the atmosphere may be too humid. This is physical and visual evidence of the importance of moisture content to maintaining fine wood furniture. It starts with manufacturing, which is why a moisture analyzer is often put to work to verify optimum moisture content before furniture is assembled.
Moisture and Wood
Newly cut wood may have a moisture content of 30%, meaning that 30% of its weight is water. That’s why anyone splitting cordwood knows that it has to be seasoned before being burned, and that the wood is much lighter after a season in the open air than when it was freshly split. Seasoning also applies to wood used in construction, and especially in the manufacturing of fine furniture.
The moisture content of wood furniture in homes changes seasonally and on average could vary from 6% to 12%. Because of this furniture manufacturers typically would work on wood with a moisture content of 8%, achieving a “happy median” through drying and storage procedures in their woodshop. An electric resistance meter can be used to gauge moisture content of inbound wood shipments, but if there is any doubt, a moisture analyzer or moisture balance can be employed to measure moisture content.
How the Moisture Balance Works
Moisture balances such as the Torbal ATS 60 available from Tovatech work on the principle of loss on drying – that is, the loss in weight of the wood during the analysis process, which is accomplished by heat.
A halogen quartz glass heater is mounted on a precision analytical balance. Shavings of wood samples to be analyzed are placed on sample plates that are mounted in a sample plate holder, placed in the test chamber, and the lid closed.
Following manufacturer’s directions, test parameters are programmed using the keypad, after which the unit is started. The moisture balance displays the weight loss as a percentage from the starting weight, the drying temperature and the drying time. The moisture analyzer will shut off when the drying is complete and the dry weight is stable, or after a specified period of time. In this case a stable dry weight of 8% moisture content would indicate that the wood can be used to manufacture furniture.
If you manufacture high-quality wood products – from chairs to pianos – a moisture analyzer should be part of your quality control operations.