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Drying Timber: An Insight Into The Kilning Process

An Introduction To Drying Timber

Over the years we’ve seen our fair share of kilns: the ‘ovens’ at the heart of every brilliant sawmill for drying timber. There is an art and science to the successful running of these hangar sized ovens to ensure prized timber, and nothing less, is achieved each and every time. Live edge tables, featuring natural and rustic beauty, have become an obsession of ours here at L’Atelier Mata. To create these stunning pieces, hardwood slabs must undergo a meticulous kiln drying process. In this blog post, we will delve into the science behind kiln drying timber, exploring the principles and techniques that ensure their stability, durability, and suitability for live edge table production. By understanding the science behind kiln drying, you can make informed decisions, optimize the quality of your slabs, and deliver exceptional products to your customers.

The Science Of Drying Timber

Once cut timber slabs undergo two to three summers stacked outside to gradually season the timber and bring down moisture levels prior to the kilning process. Kiln drying is a crucial next step in the processing of hardwood slabs, as it eliminates excess moisture, kills off insect activity, stabilizes the wood, and minimizes the risk of warping, splitting, or other defects. By reducing the moisture content, kiln drying enhances the strength, density, and dimensional stability of the wood, allowing it to withstand changes in humidity and temperature more effectively. For this very reason only the most exerienced operative, often with decades of exerience, is chosen by the sawmill to undertake the work – in most situations it is the sawmill owner her/himself!

The Science Behind Kiln Drying: The kiln drying process involves a careful balance of heat, humidity, and airflow to achieve optimal results. Several scientific principles come into play during this process.

Moisture Content and Equilibrium Moisture Content (EMC): Moisture content (MC) refers to the amount of water present in wood, typically expressed as a percentage of the wood’s weight. Kiln drying aims to reduce the moisture content to a desired level. Equilibrium moisture content (EMC) refers to the moisture content at which wood reaches a balance with the surrounding environment. The target moisture content for hardwood slabs used in live edge tables is usually around 6-8%.

Drying Schedule: A drying schedule outlines the specific temperature, humidity, and time parameters required for optimal drying. It is essential to follow a carefully designed drying schedule to ensure uniform drying and minimize the risk of defects. The schedule typically involves three stages: the initial heating phase, the main drying phase, and the conditioning phase.

Heat and Moisture Transfer: Heat and moisture transfer occur simultaneously during kiln drying. The heat energy raises the temperature inside the kiln, increasing the vapor pressure of the moisture in the wood. This pressure gradient drives moisture movement from the wood’s interior towards the surface. Proper airflow and ventilation ensure the removal of evaporated moisture from the kiln, preventing reabsorption and promoting efficient drying.

Wood Structure and Stress Relief: The structure of wood consists of long cellulose fibers embedded in a matrix of lignin. During the kiln drying process, as moisture is removed, the shrinking and rearrangement of wood fibers can create internal stresses. These stresses, if not relieved properly, can lead to warping or cracking. Conditioning, the final phase of kiln drying, allows the wood to rest and equilibrate, minimizing residual stress.

Monitoring and Control Of Drying Timber: To ensure successful kiln drying, precise monitoring and control of temperature, humidity, and airflow are paramount. Modern kilns are equipped with sensors and controllers that continuously measure and adjust these parameters, providing a controlled drying environment. In the careful introduction of heat, moisture and airflow the operator expertly creates premium quality slabs over 4 to 6 weeks of careful work!

What Can Go Wrong When Drying Wood?

There are several things that can go wrong during the kiln drying process, leading to potential issues with the wood. Here are some problems that can occur:

  1. Uneven drying: If the drying process is not carefully controlled, there is a risk of uneven drying within the wood. This can result in stress build-up, warping, or cracking. Proper air circulation and temperature control are crucial to ensure uniform drying.
  2. Overdrying: Excessive heat or prolonged drying can cause the wood to become overly dry, leading to brittleness, increased susceptibility to cracking, and potential damage to its structural integrity. It’s essential to monitor the drying process closely to avoid over-drying.
  3. Case hardening: Case hardening occurs when the outer layer of wood dries too quickly, forming a hard shell while the interior remains moist. This creates tension within the wood, which can lead to warping, splitting, or checking. Proper drying schedules and moisture content monitoring can help prevent case hardening.
  4. Internal stresses: Wood contains internal stresses that can be released or exacerbated during the drying process. Improper drying conditions or rapid moisture removal can cause these stresses to manifest as warping, twisting, or cupping in the wood.
  5. Mould and fungal growth: If the kiln is not properly ventilated or if the drying conditions are not adequately controlled, there is a risk of mould and fungal growth on the wood. This can degrade the quality of the wood, affect its appearance, and potentially lead to health hazards.
  6. Insect infestation: If the drying timber already contains insect larvae or eggs, inadequate temperature control or insufficient drying time can result in the survival of these pests. This can lead to insect infestation and subsequent damage to the wood.

Conclusion

Kiln drying timber is a scientifically driven process that optimizes hardwood slabs for live edge table production. By carefully managing heat, humidity, and airflow, kiln drying eliminates excess moisture, enhances wood properties, and reduces the risk of defects. Understanding the science behind kiln drying enables the sawmill to produce high-quality slabs, achieve dimensional stability, and deliver exceptional products to their customers (us in this case). Embracing the principles of kiln drying ensures that the natural beauty of live edge tables is combined with durability and longevity so that each table truly will last a lifetime..

What goes into sourcing timber for the finest waney edge slabs?

sawmill trip timber selection

Sourcing Timber: The Art Of The Hunt

Sourcing exquisite timber is paramount in creating our signature waney-edge dining tables. Our commitment to quality and craftsmanship drives us to go the extra mile in finding the perfect wood for each unique piece – and the extra mile often leads us to continental Europe. In this blog post, we invite you to explore our world and understand how we source and transform rough diamonds into works of art.

We invest time researching, visiting remote mills, and establishing connections with trusted suppliers. Timber, like any other crop, is cultivated for maximum bulk and uniformity so that the modern commercial sawmills can mill in the most efficient fashion. However, commercial forestry goals don’t always align with our artisanal needs as so many details are removed in the pursuit of speed (and profit). Throughout the life cycle of trees, they are managed to prioritise many criteria such as growth rate, straightness, and minimal branching etc. Unique characteristics such as movement, excessive branching, or slower growth are often seen as defects and removed. However, we value and celebrate these unique characteristics in our live-edge tables, so it’s so important to source by eye for every single piece we craft.

Our job is to uncover hidden gems with unconventional beauty. With over a decade of experience, we appreciate that our creative journey begins with selecting raw materials. When we unveil these raw boards to our clients, their initial reaction is often a gasp of disbelief, struggling to comprehend how we transform rough pieces of wood into exquisite tables. While our chapter begins at the sawmill, it’s essential to recognise the incredible individuals whose chapter ends here – the family run sawmills and the forestry team before them.

Each mill visit always leaves us with immense admiration for their skills and deep respect for the timber that binds us together. By establishing strong relationships with these mills, we have direct access to their kiln-dried stock, handpicking only the finest boards for our bespoke tables. This ensures exceptional quality and craftsmanship in each piece we create.

Leveraging our expertise in identifying standout boards, we skillfully highlight their unique characteristics, allowing clients to witness the remarkable beauty that lies beneath the surface. Transparency is woven into every step of our process. We engage our customers in every aspect, from sharing stories about timber origins to involving them in the design process, fostering a deep connection between clients and the natural materials we work with.

As we source timber for our furniture, we embrace the understanding that no two pieces will ever be identical, yet each holds its own distinct beauty. Selecting and procuring wood allows us to discover hidden treasures within. Each log tells a story, and it is our role as artisans to bring that story to life in a tangible and meaningful way.

Once kiln dried, our skilled craftsmen shape and craft the table with precision, considering the unique features and contours of the wood. Attention to detail is paramount, from the smoothness of the table’s surface to the perfect alignment of the live edges. Our craftsmen bring their expertise and passion to exceed our clients’ expectations. Throughout the creation process, we pay close attention to every detail, setting us apart and allowing us to create exceptional pieces. A protective finish enhances the wood’s natural beauty and ensures long-lasting durability. This step adds a lustrous sheen and safeguards the table against everyday wear and tear, ensuring enjoyment for generations to come.

In conclusion, sourcing timber is a labour of love and a critical part of our creative process. We journey across Europe in search of hidden treasures with the unique character and beauty we value. By prioritising craftsmanship, attention to detail, and establishing close relationships with trusted suppliers, we create remarkable works of art.