Causes:
Stains from red cedar, cypress and redwood result from a
combination of moisture and insufficient sealing. Moisture
carries water-soluble colour extracts (tannic acid)
contained in the wood through paint films. Light or medium
colours will show staining more obviously. Staining occurs
more frequently with a latex coating than a solvent or
oil-based coating.
Solution:
For Unpainted Wood
If staining occurs during paint application, use two coats
of primer before topcoating.
Wait 24 hours after application of the first coat before
applying the second and/or finish coat. Tannic acid stains
will penetrate the first coat of primer, leaving brownish
streaks or rings.
If stains do occur, reprime the stained spot, allow to
dry, and apply the finish coat.
Sometimes it is best for the new wood to weather for
several weeks prior to painting.
For Previously Painted Surfaces
Wash stained areas with a 1 to 1 mixture of denatured
alcohol and water, or with wood bleach (oxalic acid).
Rinse treated areas well, let dry, then apply one coat of
desired primer and topcoat. |
