Preservation of Timber : A Comprehensive Guide

Preservation of Timber
Timber preservation refers to the process of applying a layer of a preservation material such as oil on timber to protect it from insects, moisture, etc.

Preservation helps increase the life of the timber. A variety of preservatives are used for this purpose. Some timber preservatives can also change the colour and appearance of the wood, making it more attractive for a project.

In this article, we will talk about the different types of timber preservatives and wood preservation methods.

Why is Timber Preservation Important?

Preservation helps increase the life of timber by enhancing its durability and resistance to various elements such as insects, moisture, and weathering.

Applying a good quality preservative on timber before using it in a project will help ensure the timber lasts very long and requires little maintenance. Without preservation, the wood will go bad sooner than expected and might be damaged by insects and fungi. Preservation of wood also provides protection against water damage, which is crucial for areas like bathrooms and kitchens.

What is a Wood Preservative?

A wood preservative is a chemical used to preserve wood. It is a liquid material which is applied to wood to provide an extra layer of protection. A good preservative will protect your wood from weathering and other ailments.

Here are some other recommended properties of a timber preservative:

  • It should be easy to apply – should be able to cover a large area quickly
  • It should be free from harmful elements or chemicals
  • Should be easily available at a good price
  • Should enhance the timber’s strength & durability, not decrease it
  • Should be free from bad odour
  • Should be rot-resistant (resistant to insects, fungi, and moisture)
  • Should be resistant to fire
  • Should not get influenced by light or heat
  • Should be anti-corrosion
  • Should be able to reach the depth of the wood

Types of Timber Preservatives

There are a variety of timber preservatives available in the market. Different types of preservatives may be used depending on the wood type and a particular project.

Some of the most common types of wood preservatives include Coal tar, ASCU, Chemical slats, Oil paints, Solignum paints, and Creosote oil.

1. Oil-based Preservatives for Timber

Oil is one of the most common types of preservatives used to protect wood. Different oil-based preservatives are commonly used for this purpose. One popular example is coal tar.

Coal Tar is a thick liquid oil which is heated to obtain a lighter hot tar which can be easily applied to a timber surface to enhance its durability. The tar is generally applied using a brush. It is most commonly used for timber intended for outdoor use but can also be used to preserve marine timber which is used in marine applications to provide protection from water damage. It is one of the cheapest types of timber preservatives and offers resistance to fire and water. One drawback of using coal tar is that it doesn’t allow paint on it.

Oil paints are applied to wood to provide protection against moisture. This type of preservative contains paint based on oil. Generally, two or three coats of paint are applied to ensure strong protection. However, oil paints can be applied only to well-seasoned (dried) wood, otherwise, it might result in the decay of timber.

Creosote oil is produced from the purification of coal tar. It is dark brown or almost black and is less thick than tar. It is usually applied to well-seasoned timber to provide protection against termites, water and other things. It is commonly used for railway sleepers and poles. It is non-corrosive and has an unpleasant odour. Like any other oil-based preservative, creosote doesn’t allow paint on it.

2. Water-soluble Preservatives

ASCU is a water-soluble type of preservative, which comes in powder form and is mixed with water in a 6 (ASCU) to 100 (water) ratio to prepare the preservative solution, which is then applied to the timber surface generally by spraying. It is mainly used to provide protection against insects, particularly white ants. It allows paint on it, i.e. the timber can be painted after applying ASCU.

Chemical salts are another water-soluble type of preservative that is commonly used to preserve wood and enhance its strength. It is dissolved in water to make a solution which is applied to wood. It is anti-inflammatory and has no odour. Copper sulphate, mercury chloride and zinc chloride are common examples of chemical salts used for timber preservation.

3. Solignum Paints

Solignum Paints are a special type of chemical-based wood preservative, which are available in the form of termiticides and decorative coatings or paints and can be applied to wood to provide protection against a variety of insects, including white ants. One of the benefits of these preservatives is that they are available in different colour options and will enhance the appearance of your wood.

Methods of Applying Timber Preservation

The process of timber preservation involves applying a preservative on the surface of the wood and allowing it to settle before using it in a project. This is usually done during the wood processing stage, generally after drying the timber properly.

Different methods can be used to apply preservatives to wood, depending on the wood type and the intended use. These include spraying, brushing, injecting with pressure, charring, dipping, and open tank treatment.

1. Preservative Application on Timber Surface

This type of timber preservative application method involves applying preservatives on the surface of wood by spraying, brushing, or dipping.

1.1. Brushing

As the name suggests, this timber preservation method involves the use of a brush to manually apply preservatives to the wood surface. All sides of the timber are properly coated with the preservative.

1.2. Dipping

The piece of timber is dipped in a container filled with a preservative solution and left for a limited period of time to allow the preservative to fully cover the surface of the timber. This results in stronger and better-protected wood.

1.3. Spraying

A sprayer machine is used to spray the preservative solution on the wood surface. It is quicker and more efficient than brushing but less effective than dipping.

2. Preservative Soaking Application

In this type of timber preservation method, the freshly sawn wood is dipped into a pool of preservatives, where it is left for a considerable period of time to allow the preservatives to get adequately soaked into the timber. The soaking time depends on the type and thickness of the timber. Thin veneers need to be soaked for a couple of minutes while thick boards might need to be soaked for much more time.

3. Injecting Under Pressure

As the name suggests, this timber preservation technique involves injecting or forcing preservatives into timber through the application of pressure under specific temperature conditions. It can be creosote oil or any other suitable wood preservative. This method usually needs a special set-up and might be expensive.

4. Hot & Cold Timber Preservation

In this method of wood preservation, the timber is first dipped in a pool filled with a preservative. The wood is then heated at a predefined temperature and maintained the temperature for some time to allow the air inside the timber to expand and some of it leaves the wood. Then, the timber is allowed to cool down, which causes the remaining air inside it to contract, which drives the wood fibres to absorb the preservative to fill the vacuum inside.

Besides providing a protective layer, this method of wood preservation also sterilises the timber to make it free from fungi and insects. This method can achieve the nearly same results as the pressure treatment method.

5. Timber Preservation Using Charring Method

This is a traditional method of wood preservation which involves burning the surface of timber up to 15mm to create a natural protective layer which protects the inner timber from insects. The wood is first submerged in water for up to 30 minutes and then burned. This type of treatment is not suitable for outdoor wood applications and is generally used for fencing poles.

Want to Know more About Timber Preservation?

Contact Cameroon Timber Export Sarl to consult with one of our wood specialists to learn more about the best timber preservation techniques and products. If you’re looking to buy top-quality sustainable timber, wood, plywood or other wood products, visit our website or call us to get a quote.