Why is Kiln Dried Wood Best for Worktops?

Before our wood is constructed into worktops, the timber goes through an intensive kiln-drying process to enhance quality and durability. In this guide, we will discuss this process of kiln drying in detail, and will also explore why such a treatment is necessary.

Wood and Moisture

It may seem obvious that wood has a high moisture content – after all, trees cannot grow without vital liquids that deliver key nutrients. However the moisture content in a piece of timber can have a profound effect on its performance, meaning that it is crucial that timber is dried in the correct way (in order to guarantee that the resultant timber is of a high enough quality to make wooden worktops).

Even when your worktop is in place, it will continue to absorb or lose moisture until it reaches the same ambient level in the surrounding space. This process is commonly known as equilibration, and can cause issues if the wood is not dried sufficiently before manufacture. The most common problems occur when the wood has been dried too quickly, leading to uneven shrinking, cracks or other damage.

The timber used for our wooden worktops is dried very soon after the tree is felled. This speed is crucial to ensure that the timber is protected against decay, fungal infections and other types of infestations.

There are plenty of other beneficial side effects from the drying process including:

• Decreased weight.
• Increased strength.
• Better insulation properties.
• Easier to work, glue and finish.

For further information about how moisture affects wood, read our ’Wood Movement’ guide.

The Drying Process

Kilns are essentially a large oven that has an over-sized chamber, in order to fit in plenty of timber simultaneously. Depending on the size of the operation, a kiln can be the size of an entire warehouse, or substantially smaller.

By kiln drying rather than air drying, more moisture is removed, and in a more even fashion because of the consistent heat applied to all areas of the timber. The additional heat also means that drying times are considerably faster than if timber is left to dry naturally.

As well as the lessened opportunity for fungi and other infestations, it also means there is no variance in drying times depending on seasonal or climactic variations. Compartmental kilns are the most commonly used, with separate ovens that can be filled with isolated batches of timber, and dried until a specific moisture level is detected. These multiple ovens mean that different thicknesses, quantities and even multiple species of wood can be dried at the same time.

Modern kilns use high-tech computer systems linked to a variety of sensors, which ensure that the kiln automatically shuts down when each load reaches its optimum moisture level. These systems are the result of extensive research into kiln drying, as without these specialist controls, kiln drying wood on such a large scale would be inexorably expensive.

There are four main components of a timber kiln:

• Heating. Depending on the age and type of kiln, this could be an electric or gas-powered heating element, or a form of steam heat exchanger.
• Chambers. Whilst in earlier kilns, the chambers were usually constructed from brick, newer kiln chambers are made from aluminium or another sheet metal in conjunction with other thermal insulation materials.
• Humidification. Where the amount of moisture in the air needs to be strictly regulated, steam is pumped into the compartments. Ventilation systems help control the humidity and extract any excess evaporated water from the kiln as the timber is being processed.
• Air Circulation. Heat on its own would very unevenly dry the wood, so each kiln has an extensive air circulation system which helps extract evaporated moisture, and ensure that temperatures are even throughout the chamber. Some smaller chambers are able to create a vacuum to make the process of removing the moisture even faster.

To find out more about origination of our wooden worktops, read our comprehensive ’Sourcing and Manufacture of Solid Wood Worktops’ guide.