Untreated, dried timber is first loaded into a large cylinder tank where a vacuum is applied and all of air extracted from the tank. The treatment tank is then filled with a water based preservative. Once filled, hydraulic pressure is applied to the tank, this enables the preservative to penetrate the timber allowing the product to reach the desired treatment class. There are various classes of timber treatment depending on where the end-product timber is to be used. After a set amount of time, another vacuum is applied to the tank to extract the remaining, unabsorbed treatment. Finally the low pressure inside the timber allows for the treatment to be absorbed even further into the wood, thus allowing for even better protection. The timber is removed from the tank and left to dry before being passed on to the final consumer.  Initially this treatment leaves the timber a green colour given the copper used in the treatment. This will eventually fade over time turning the product a silvery/grey colour as the timber weathers. This change in colour does not mean that the timber is any less protected than it was when it was green. It is simply the wood adjusting to its surroundings. 

So why is this treatment so important? Simply put, it greatly prolongs the service time of the timber when it is used outdoors. The treatment protects against wood decay, rot and insect attack. If it weren't to have this treatment, you would find that you would be replacing fencing and decking every few years. Furthermore, some timbers have a greater absorption rate than others, pine (which we use) is a naturally absorbent timber hence soaks up the treatment better than other timbers.