This refers to stains that appear as a result of a waxy substance in reconstituted wood products like chipboard or MDF. When these products are painted, these staining substances can bleed through the paint – even through some ordinary primers. This can cause dirt pickup, fungal or algal contamination, and/or poor paint adhesion.
Failing to apply a proper primer to hardboard before applying a topcoat.
Apply a quality water-based acrylic primer, followed by two coats of quality acrylic paint.