responds: Unless you shrink-wrap each
piece of cedar, it will darken and eventually
weather to a silvery gray, or worse, to a blotchy
dark gray. Clear finishes with UV inhibitors will
slow down the weathering process, but these still
need to be reapplied every two years or so.
Eventually the color will change anyway, even
The best thing you can do is to approximate the
color of new wood by putting on a cedar-tone stain.
First, install the siding with the rough side out.
A smooth surface holds less finish and weathers
much quicker than a rough-sawn surface. Finish the
rough surface with two coats of a
lightly-pigmented, semitransparent, oil-based
stain. Be sure to choose one that contains a water
repellent and a preservative or mildewcide for best
performance. Apply the first coat and let it soak
into the wood 20 to 60 minutes and then apply the
second coat. If you allow the first coat to dry,
the second coat cannot penetrate into the wood.
About an hour after applying the second coat, use a
cloth, sponge, or dry brush to remove any excess
stain. Otherwise, the stain that does not penetrate
into the wood will form an unsightly film and
glossy spots. Two coats of oil-based stain on rough
wood will last from four to eight years, depending
on the weather conditions it is exposed to.
If you have weathered and discolored wood
siding, you can regain the new look of cedar by
cleaning off the dirt and mildew with a solution of
one third cup liquid household detergent (be sure
it is ammonia-free), one quart liquid household
bleach (containing 5% sodium hypochlorite), and
three quarts warm water. Follow this up with a
water rinse and then use an oxalic acid bleach
solution made with about a half pound of oxalic
acid per gallon of water. Be sure to rinse with
water again. This oxalic acid bleach solution will
draw out the tannins in the wood and revive the
orangeish tone of the cedar. At this point, you can
let the wood weather naturally, or apply the
cedar-tone semitransparent stain.
— William Feist is a research chemist
who specializes in coating technology at the Forest
Products Laboratory in Madison, Wis.