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Timber Kiln Drying

The importance of kiln drying in the timber stabilisation process.

Here at WM timber, we have been selling professionally kiln dried timber slabs for over 15 years to our ever-growing list of wonderful clients.

We believe the correct drying process for timber slabs takes time and can’t be fast tracked! We know it’s hard to stop yourself from getting stuck into a nice big timber slab with a sander to reveal the beauty beneath after a few weeks, months or even a year of air drying! However, we can guarantee, your headed for disaster! and an expensive one at that!

The kiln drying process

The moisture content in freshly milled timber slabs can vary from species to species. Green timber has a high moisture content, typically between 40 – 70% which needs to be removed before use. Pre-drying slabs is a slow process as moisture moves from the core to the surface. Airflow on the timber surface slowly evaporates the moisture until it is in balance with the surrounding environment. To achieve successful air drying the slabs are stacked in such a way as to allow even airflow. This air drying process is referred to as seasoning of timber.

Using unseasoned or green slabs in your project could result in shrinkage, twisting, warping and cracking of the slab, also popping of any resin that has been applied and bubbling/peeling of varnish or polish.

How does timber kiln drying work?

At WM Specialised timber we ensure all our timber slabs are air dried for a minimum of 1 year and in most cases 3-4 years before kiln drying. If kiln dried too soon in the drying process the slabs core moisture content may remain high. Drying timber too quickly causes cracking and warping.

Kiln drying is necessary to further reduce moisture content to below air drying levels. Our slabs are dried in a low temperature high humidity gas fired kiln. We start the process with high humidity (90%) and low temperature then slowly reverse this to achieve higher heat and lower humidity, slowly reducing the moisture in the core of slab and minimising damage to the slab surface. This usually takes around 3-6 weeks depending on timber species and initial moisture content. We aim to achieve a core moisture content of between 9-13% with 10-12% being ideal for timbers in Victoria.

Once removed from the kiln we dress all our slabs with a wood wizard, sand them to 80 grit then add them to our beautiful showroom ready for their new life as a bar top, tabletop, shelf or any other project you might have in mind.

Some additional handy advice

Please Note that we don’t recommend leaving your timber slab out in the elements, as they will reabsorb moisture and may warp and crack. For large slabs we always recommend good fixings to steel legs or timber substrates and that the slab be sealed on both sides and all edges with a quality oil. We recommend Osmo oil, which also comes with a UV protection for slabs that are exposed to the harsh elements of the Australian sun.