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Discoloration
Cedar enjoys a well-deserved reputation as
a wood that takes and holds a range of finishes
for extended periods. Nevertheless, the normal life
of a finish will be shortened by degradation and
discoloration. The causes of degradation are many
and have been discussed in the preceding pages.
The causes of discoloration, though not in themselves
a failure of the finish, often requires remedial
treatment.
Dirt
Dirt is the most benign cause of discoloration
and not usually a problem. A periodic cleaning
with a mild detergent solution will usually restore
the surface finish.
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Mildew
Mildew applies both to the fungus and to its staining
effects on both the finish and the wood. Mildew is a common
cause of discoloration of paint, solid-color stains and
natural finishes. Restaining does not solve a mildew problem.
When it is time to refinish, clean off the mildew with
a commercial mildew-remover then refinish with a coating
that contains an effective mildewcide.
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Extractives
Bleed
Extractives bleed that discolor the finish is usually
caused by moisture. To stop stains caused by extractives
bleed, moisture problems must be eliminated. Mild
staining is often washed away by rain over a period
of weeks. In sheltered areas of the building where
the stain persists, it may become darker with age
and more difficult to remove. If washing with a
mild detergent solution does not work, a commercial
cleaner may help.
Iron Stains
Iron stains may appear in two forms: the reddish
brown discoloration caused by rust, and blue-black
discoloration caused by the reaction of iron from
nails and other metal objects with extractives from
the cedar. To prevent these stains, use only hot-dipped
galvanized, aluminum or stainless steel nails when
fastening cedar.
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Water Stains
Water stains often occur in combination with extractive
bleed and mildew growth. These stains can be difficult
to remove. Scrubbing the wood with an oxalic acid solution
is sometimes effective.
Caution: Handle oxalic acid solution with care
as it can be harmful.
Chalking
Chalking is a property of the paint, not the cedar.
It occurs when a paint film weathers or deteriorates,
releasing pigment particles that act like a fine powder
on the paint surface. Chalking is a common cause of
fading of tinted or colored paints.
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