Wood Drying and Seasoning Quiz

Wood Drying and Seasoning: Methods and Benefits

• Wood drying or seasoning reduces the moisture content of wood for better structural stability and combustion.
• Kiln-drying is the modern method of wood drying, while air drying is the traditional method.
• There are two main ways of seasoning timber: natural (air) and artificial (kiln) drying.
• Both methods require the timber to be stacked and separated for complete air circulation.
• Air seasoning is done with the timber stacked outdoors, while kiln seasoning is done in a controlled environment.
• Seasoning of timber reduces the moisture content to that of the surrounding air, improving durability and load-bearing properties.
• Natural or air seasoning involves stacking the timber with wide spaces between each piece and using strips of wood between each layer for vertical separation.
• Air-drying is a slow process, typically taking 6 to 9 months for hardwoods to reach a moisture content of 20-25%.
• Artificial seasoning involves using forced air drying or kiln drying for faster results.
• Forced air drying uses fans to circulate air, while kiln drying involves a controlled environment with humidity and temperature regulation.
• Reasons for seasoning include preventing shrinkage, splitting, checking, and warping, achieving greater stiffness and strength, allowing penetration of preservatives, and obtaining a surface that will accept paint, polish, or glue.
• Proper seasoning requires stacking the timber safely, sealing the ends, raising the stack off the ground, and providing overhead cover from direct sunlight and weather effects.

Methods and Chemicals for Wood Treatment

• The pressure method of wood treatment includes various processes such as the Bethel/Full cell process, Lowry process, empty cell process, card process, and open tank treatment.
• Brushing/coating method is the simplest and least efficient method of wood treatment, while the spraying method is more effective for treating large areas.
• The sap-replacement method involves fixing a newly peeled shaft with a sap containing a preservative solution that is slowly forced through the pores of the wood.
• The common causes of decay in wood are alternative moisture and dryness, fungi and molds, insect and worms, heat, and confined air.
• Wood preservatives are chemicals that enhance the durability of timber treated with different methods and are classified into three main groups: tar oil preservatives, waterborne preservatives, and oil-borne preservatives.
• Tar oil preservatives are effective against fungal decay and insect attack, are not corrosive to metals, and are easier to apply by brushing, spraying, or soaking.
• Waterborne preservatives consist of salts of copper, zinc, etc., dissolve in water, and leave wood in a clean condition that can be painted even after the water has dried.
• Oil-borne preservatives are effective against decay, are not corrosive to metals, and can be applied by brushing or spraying.
• The effectiveness of preservatives depends on their high toxicity towards wood-destroying organisms, permanence in treated wood, ability to penetrate deeply in wood, freedom from deleterious effects on the wood itself, and non-corrosiveness to metals.
• The amount of preservative infused into the wood varies from 10-25 lbs/sq.ft for the Bethel/Full cell process to 1.2-2 gallons for the empty cell process.
• Wood treated with preservatives can last for many years and is used for various purposes such as railroad ties, roofing, and construction.
• The use of wood preservatives is essential for sustainable forestry practices, reducing the need for harvesting new timber and contributing to the circular economy.