August 2013

Removing Redwood Stains With Oxalic acid

Naturally occurring chemical extractives in redwood are in large part responsible for its beauty, stability and durability; however, sometimes these water soluble extractives migrate to the wood’s surface. High concentrations cause a discoloration referred to as extractive bleeding. Extractive bleeding appears in several forms. Some boards, high in extractive content, may turn very dark if unprotected by finishes and exposed to moisture. Extractives may bleed through paints if stainblocking oil or alkyd primers are not used.