Wax Bleed

Definition

Unsightly discoloration or a “wetting effect” on hardboard siding. The wax comes from the additives used to make the board more moisture-resistant.

Causes

• Failure to apply the proper primer to the hardboard before painting
• Allowing hardboard siding to weather before painting
• Use of dark paint colors, which absorb heat and can accelerate wax bleed
• Too little paint; wax bleeding is more likely in thinly painted areas
• Applying a hard finish over a softer coat without priming, or painting over a glossy surface without sanding
• Using low-quality paints, whose low levels of resin allow wax to bleed through the paint film

Solutions

• Unprimed boards should be primed or painted within 30 days. Factory-primed boards should be painted within 90 days of installation.
• On unprimed boards, apply the recommended primer and two topcoats. Follow the recommended film thickness application on the label.
• Select top-quality, oxidative primers and topcoats for unprimed hardboard to help prevent wax bleeding.
• First determine if wax bleeding is the problem:
  • Place a few drops of bleach on the discolored area. Household bleach does not affect wax so if there is no whitening or bleaching, the stain is likely wax.
  • Place a few drops of water on both normal and discolored areas. If the water beads up and runs off, a wax film probably exists.
  • Rub the area with your finger. In severe cases, the wax feels like an oily substance. a few drops of bleach on the discolored area. Household bleach does not affect wax so if there is no whitening or bleaching, the stain is likely wax.
• Place a few drops of water on both normal and discolored areas. If the water beads up and runs off, a wax film probably exists.
• Rub the area with your finger. In severe cases, the wax feels like an oily substance.
• If the wax is light or moderate, the area can be cleaned with a detergent solution. In cases of severe bleeding, the surface must be cleaned thoroughly with mineral spirits. Dispose of all waste materials in accordance with local regulations.
• Allow the surface to dry thoroughly before priming. Prime the surface with a high-quality primer and finish with the recommended Dunn-Edwards top coat.