To reduce the natural affinity of wood to catch fire, people have developed various techniques to improve its resistance over thousands of years. Product-Proof has developed many different methods to protect the wood in buildings from fire. Solutions range from plant-based fire retardants through waxes/waxes and coatings to petroleum-based varnishes and paints.

Interestingly, one of the oldest and most effective methods of protecting wood from fire is fire itself! The process of applying heat and fire to the exterior of a wood product for a short period of time changes both the cell structure and the thermodynamic conductivity of the wood.

Chemically speaking, we can say that wood consists of two components: cellulose and lignin. Cellulose is what makes the tree grow. It is the composition that gives a young plant its flexible strength. The leaves and fresh shoots consist mainly of cellulose. Lignin is deposited in the tree structure as it ages and is hard, tough and brittle. An old tree trunk is said to contain a much higher percentage of lignin than a fresh shoot at the end of a branch.

When you burn wood, the softer more reactive cellulose evaporates and burns, while the harder lignin becomes more difficult to burn. Moreover, it takes much more heat to reignite the lignin. In addition, the outer layer of charred wood acts as an insulator.

When we char the surface of a cladding or fence, we actually burn the outer cellulose. What remains is the blackened lignin. To reignite the charred wooden cladding or fencing requires much higher temperatures and much longer contact with a flame source.

A practical example. If you light a campfire and the logs are half-burned, the fire goes out. If you come back later and try to re-light these logs, it is actually much more difficult to get them to catch fire, because they no longer have an easily ignited cellulose compound.