The Problem: A common exterior paint issue, wax bleed is a discoloration of the paint film caused by additives used to make reconstituted hardboard siding more resistant to moisture. These wax additives can bleed through low grade primers and paint causing dirt pickup, mildew and poor adhesion.
Causes: Failing to apply the right primer to the hardboard before painting. Allowing the hardboard siding to weather prior to painting. The use of dark paint colors which absorb heat and can accelerate wax bleed. Over spreading the topcoat resulting in thinly painted areas. Using a low-quality paint that allows wax additives to bleed through the paint film.
How-to-fix: A high-quality primer should be applied to the hardboard within 30 days. Factory primed boards should have a topcoat applied within 90 days. Two coats of high-quality exterior latex paint is recommended for the topcoat. Please note the low-quality paint with dark colored flat finishes are more prone to wax bleed.