Wood is a renewable resource that, when treated properly, will last a lifetime with minimal decomposition and little need for replacement. Wood decays when moisture or insects attack it, allowing further breakdown by fungi and bacteria. Using borax and diesel to treat wood allows do-it-yourselfers to protect their lumber with ingredients that are readily available and easy to use. They are both inexpensive and have specific advantages, depending on the use of the wood.
Add one and one-third cups borax to one quart of water in a metal mixing container. Borax is a compound of boron and oxygen, and resists beetles, termites and fungi. It is odorless and colorless and does not change the color of the wood. It is minimally toxic to mammals and should only be used outdoors.
Treat the wood by painting up to three coats of the borax solution, allowing each coat to dry before applying another coat. Apply a coat of acrylic sealant over the borax to seal out moisture. Borax-treated wood works well in covered porches and other external areas of the home, as well as garden applications.
Mix one quart of copper naphthenate, with three and one-third quarts of diesel in a metal mixing container to dilute the copper concentration to 2%. Copper naphthenate is a preservative that requires an oil-based solvent as a carrier medium. It works very well with diesel fuel. Copper naphthenate is available commercially at most lumberyards.
Brush on two coats to the wood being treated, allowing each coat to dry before adding another. Apply only to wood surfaces above the ground, such as poles, fences, steps or decorative timber.
Wear protective gloves and a facemask while applying copper naphthenate solution with brushes. Copper naphthenate and diesel solution is only suitable outdoors. Use it in locations that do not have a lot of foot traffic. The preservative has a strong, unpleasant odor, even after it has completely dried.