You've thought long and hard and decided that treated pine is the best choice of material for your raised garden bed. In order to cut costs, you've thought of buying used pine sleepers that you'll re-treat and re-use to build a home for the roses and tulips that make your backyard such an inviting place.
Initially, this may sound like the perfect plan. However, you might reconsider this once you learn what it would take to treat used pine sleepers on your own. Here is a brief overview.
A Pool Of Creosote
Creosote is a derived from the distillation of coal tar and it often has a brownish-black appearance. It's among the more commonly used wood preservatives and it will leave your untreated pine with a black or a dark-brown appearance after treatment.
Treating used sleepers using creosote will require you to pour the preservative in a trough before you immerse the sleepers into the trough. Leaving sleepers immersed in creosote for a day or two allows them to absorb the preservative, hence treatment.
This treatment method may seem attractive due to its simplicity. However, there's the risk that your used sleepers may not absorb creosote uniformly and this means that certain parts of the sleepers may remain largely untreated.
A Hot Bath And A Cold Bath
You can also treat sleepers using thermal treatment. This treatment method will require you to have hot creosote in one tank (preferably a steel tank) and the cold preservative in another.
The sleepers are immersed in the hot creosote for a few minutes in order to expand air that they contain. As the air expands, some of it is forcibly released from the wood. They are then immersed in the cold creosote. This results in the contraction of air will have remained inside the sleepers. As the air contracts, creosote is "sucked' into the used sleepers. To ensure that enough creosote is sucked in, you may be forced to repeat the process described above several times for each sleeper.
Copper Sulphate And Sodium Chromate
If you'd rather avoid handling creosote, double diffusion might be the pine treatment option for you. For this process, you need to buy crystals of copper sulphate and crystals of sodium chromate (you can get both from online stores). The crystals are dissolved in water to make two different solutions.
Pine sleepers are immersed in the copper sulphate solution for a few minutes before they're immersed into the solution of sodium chromate. This allows both solutions to diffuse into the sleepers. The two solutions then react to form copper chromate inside the sleepers. The toxicity of copper chromate will keep insects and fungi away from your raised garden bed.
New, treated sleepers for your raised garden bed don't sound so expensive anymore, do they? For more information, contact companies like Australian Treated Pine.