A guide to timber treatment: heat treated vs. kiln dried wood

When it comes to timber treatment, there can be some confusions on the differences between heat treated and kiln dried wood. Wooden pallets are used to transport millions of items every day, and damaged wood can be a costly problem. ISPM15 regulations require all wooden forms of packaging are heat treated before they are used for export, so it’s important to understand the differences.

Read on to find out more about what heat treating and kiln drying pallets really means.

What is heat treating and what is kiln drying?

Kiln dried refers to timber that has been dried in a kiln to reduce moisture content. Moisture in timber can cause lots of problems – including twisting, cracking, and shrinking – incurring costs for damages. Kiln drying serves to bring moisture levels down to a workable range.

Heat treated refers to wood that has been heated to a specific temperature, essential for international shipments and national deliveries. Untreated timber can be a hotbed for pests and diseases, which can be easily transported from one area of the world to another. Heat treating pallets is a necessary step to ensure pests and diseases are not carried abroad.

What is the difference between heat treated and kiln dried?

The key to understanding the difference is to understand the main aim of each form of timber treatment.

Kiln drying is used to reduce the moisture content of timber. By extracting the moisture in a kiln to below 15%, the wood is lighter (and cheaper to transport) and reduces the chance of discolouration later.

The goal of heat treatment is to eliminate any living organisms in the wood, and to ensure pests and diseases are not introduced to other countries during shipping.

How do we heat treat our wooden pallets?

Wooden pallets must be heat treated in accordance with ISPM15 guidelines that lay out the specific temperature and duration.

ISPM 15 stands for International Standards for Phytosanitary Measures No. 15 and is the industry standard regarding wooden pallets. It was established to prevent the risk of spreading pests and diseases around the world. It requires that all wooden forms of packaging (e.g. pallets) are heat treated before being used for shipping. The standard has been adopted by all members of the European Union and 14 other countries globally.

Our wood packaging is heated in our specialist onsite kiln for approximately 3 hours, ensuring the wood core temperature reaches a minimum of 56°C for at least 30 minutes.

How do we kiln dry our wooden pallets?

Just like heat treated timber, wood is heated in a kiln. However, kiln drying is a much longer process with a gentler heat. The timber stays in the kiln for upwards of 3 days, where the moisture is extracted into the air, lowering the moisture content of the wood to below 15%.

What are the benefits of kiln drying pallets?

Unlike wet timber that has been left to air dry, kiln drying pallets reduces the risk of the pallet splitting. The reduction in moisture means the weight is also reduced, making them cheaper for export as the transportation cost is charged by weight.

The dryer surface is also better for moisture-sensitive products, such as paper and cardboard. The reduced moisture also decreases any discolouration.

What are the benefits of heat treatment?

Although less moisture is removed during the heat treatment process than kiln drying, moisture is still removed, making the pallets lighter and cheaper to transport.

Parasites in the wood are removed, reducing the spread between countries. Heat treatment also increases a wooden pallet’s durability, creating pallets that can be recycled and reused, helping to reduce waste.

Kiln drying is not a reliable way to kill insects in wood, owing to the cooler temperatures used during the kiln drying process compared to the more intensive heat treatment process. The dryness may eradicate some of them, but the lethal temperature required to kill woodboring insects varies considerably.

Facts about heat treated pallets

Visually, timber that has been heat treated can sometimes look darker, due to the the sap in the timber reacting to the heating process. Heat treated pallets are also stamped with an authentication mark that is recognised worldwide. This proves that the wood has been heat-treated appropriately and is free from pest infestations.

This authentication will last the lifetime of the pallet so, once it has been heat treated to ISPM15 standards, the pallet can be reused to ship and transport goods globally without the need for re-treatment. Wooden pallets can last for up to ten years, and later be recycled into furniture and other home projects.

Contact us for heat treated packaging today

We can make packing cases, pallet collars and supply any form of wooden packaging. Please get in touch to let us know your requirements.

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