Preparation for Initial Application of WOODguard
Both new and weathered wood should be cleaned prior to your WOODguard application. New wood may have mill glaze or planers crush; weathered wood may have collected contaminants from pollution or the beginnings of decay.
Cleaning Materials: Make a solution of 4 oz. of Oxalic Acid Crystals in 1 gallon of water; a stiff-bristled nylon brush; a garden pump sprayer; and power washing equipment set below 500 psi.
Procedure: Working in small, manageable sections from the bottom up, wet the wood with water, then generously apply Oxalic Acid solution using the garden pump sprayer. Keeping the surface wet, scrub the surface with a stiff-bristled nylon brush for 15 to 20 minutes. Do not let the solution dry on the wood. Then, power wash the Oxalic solution off the surface with clean water from the top down.
To avoid wood damage and achieve maximum effectiveness, make sure the pressure is set below 500 psi, and keep the nozzle of the power washer approximately one foot from the surface. A garden hose is not sufficient for this purpose, as it typically provides a maximum of 60 psi. Measure the pH of the rinse water at several places to make sure the water run-off is between 6.0 – 7.0 to assure that all of the oxalic acid is removed. If all of the oxalic acid is not removed the wood will develop a dark chocolate color. The pH strips from 6 to 9 are available at local drug stores, pool supply stores or discount stores. Let the surface dry for three days before applying WOODguard. When applying any chemical to wood on a vertical surface, ALWAYS apply from the bottom up to eliminate drip or run marks.
