The problem appears as a splotchy dirt collection. This discoloration can resemble mildew growth, yet will not change color when washed with household bleach.
An excessive amount of wax on the surface will cause the coating to peel down to the substrate.
- Stains that come from waxy substances in the reconstituted wood products used to make hardboard siding.
- These staining substances bleed through the primer and paint, possibly causing dirt pickup, mildew, and/or poor paint adhesion.
- In severe cases, substance can be felt with the fingers as oily or waxy.
The discoloration can be identified by applying household bleach to rule out possible mildew. The presence of wax will not be affected by bleach.
Apply a few drops of water to the board surface. If the water beads up and runs off the board, a wax condition is indicated and must be removed.
Scrub the entire surface with a cleaner designed to remove waxes, such as a liquid deglosser. Rinse thoroughly with plain water.
Rescrub areas where water continues to bead up on the surface to ensure that wax deposits are removed. Allow surface to dry thoroughly before priming with Exterior Oil-Based Wood Primer.
Bare hardboard surfaces should always be primed with Exterior Oil-Based Wood Primer first.
If the condition is severe or anticipated to continue, possibly coating the surface with a light color might reduce the occurrence; dark colors tend to heat up much more than light colors causing more of the waxes to melt and leach out.