Measuring Moisture in Wood.

Wood surrounds us in everyday infrastructure and furnishings. Despite this, people generally give little thought to how the wood was made safe for its final destination. Wood was once a part of a plant and is made of a complex cellular structure. As is the case with cells, the wood can readily absorb and retain moisture. Treatment of wood and wood products may involve drying or humidifying in order to achieve the desired moisture content for the wood. Too little moisture can reduce resiliency and flexibility of the wood, which results in cracking. However, too much moisture can make wood prone to decay and softening. Both of these deficiencies lead to wood being unstable, resulting in products of reduced lifespan and quality. Once wood is heat or humidity treated, a type of sealant such as paint, varnish, oil, or stain may be applied. Too much moisture prior to sealing can cause damage to the treatment. Further, if the wood is unsealed, moisture can creep in overtime and compromise the stability (wood strength, flexibility, durability, quality) and lifespan of the wooden structure.

Moisture content is most important during processing, but is also relevant postproduction if further wood treatment is needed. For example, if wood is received in a dried condition but the ambient moisture is 15%, this could cause the moisture to exceed 20%. Excess moisture results in paint bubbling and peeling as well as discoloration. Finishes on the wood can influence the amount of moisture transmitted into the wood during its working life. Water-based finishes and porous finishes such as paint are more permeable and do not repel water and moisture as effectively as moisture repellent finishes such as a film- forming finish. Finish choice can be influenced by the moisture retention of the wood.

Application:

A wood fabrication company contacted Hanna Instruments to find a solution to an issue they were experiencing with their new finish. The company was starting to shift into more eco-friendly practices and had changed to a water-based varnish. While the benefits of the new varnish were substantial, they were having issues with the glossiness of the finish. Instead of a high-gloss varnish, it was coming out duller compared to the samples from the varnish manufacturer. The wood fabrication company wanted to measure the moisture content of the wood before and after treatment to determine if they needed to change their drying and storage practices for the wood in order to maintain the proper finish.Hanna Instruments recommended the HI903 Karl Fischer Volumetric Titrator for accurate determination of moisture in the wood. The HI903 can measure up to 100% moisture, accommodating the entire range of products that the customer wanted to test. Due to wood’s cell structure, an external extraction was suggested to release the water over the course of several hours. An external extraction removes moisture from the wood using a non-aqueous solvent. The titration is performed on the extract once all of the moisture in the wood is extracted. The customer appreciated the titrant recordkeeping and titrant database capability of the titrator, as they would have to use different titrants depending on the sample material. The customer valued that the titrations would take much less time than determining moisture by loss on drying. The HI903 provided a precise and complete solution to their moisture content measuring requirements.