Does House Paint With Primer Keep Stains From Bleeding Through?

Causes of Stain-Bleed

• Surface preparation is the key to preventing stains from bleeding through a paint job. Preparation may, however, go deeper than the immediate surface to be painted. Many stains, like rust, mildew and mineral marks, are water-related. Surfaces need to be dry before painting but, more important, the cause of moisture needs to be addressed. Otherwise, stains will return. This is especially true of rust and mildew stains. Both spread easily in the presence of returning moisture. Other stains may require different prevention strategies. Chemical or highly pigmented spills, like paint or wood stain, need to be removed as completely as possible before painting proceeds. Just adding an extra coat of paint may not be enough to keep chemical reactions from continuing and bleeding through paint. Oily substances also need to be removed or neutralized before painting, not just covered.

How Primer Works

• Tim Carter, author of Ask the Builder, suggests regarding all paints as varieties of glue with pigment added. The first attribute of paint is its ability to stick to surfaces. Usually white or a neutral color, primers create a strong bond with surfaces and an equally strong potential bond for decorative top-coat paint. Experienced painters note that primers are sometimes thinner than top-coat paint and tend therefore to soak into surfaces rather than sit on top. Primer is further formulated to be less air-permeable, or breathable, than acrylic or latex top-coat paints. These attributes contribute to its capacity for covering stains. Binding to and soaking into the stain with a finish that does not let moisture or air travel freely through to the surface mean primer covers stains well and can help keep them from bleeding through top-coat paint.

How Top-Coat Paints Work

• Top-coats are formulated to provide a seamless, smooth surface. Top-coats bear the complex pigments that produce and sustain wall color and are creamy-thick, meant to float on top of wood, plaster, masonry and other structural materials. This thick coat also should help repel rain, wind, strong sun and other weather damage, while letting excess moisture escape through its pores. The same breathability that keeps excess moisture from accumulating and blistering paint can, if in direct contact with the stain, let staining bleed through, which primer will not.

Paint/Primer Combinations

• Periodically, paint manufacturers have tried to ease the work load of painters by combining primer and top-coat functions in a single paint. Opinions among amateur and professional painters about current formulations and coverage of paint-primer combinations often differ, so your best strategy to determine whether a paint with primer combination will provide the stain coverage you need is to choose a small or lightly-stained project to test these two-in-one paints on. While Sherwin-Williams, Behr and Olympic have all moved strongly into the combination market, some self-priming claims may apply only to previously painted surfaces. Manufacturers emphasize surface stain resistance, but long-term stain-bleed capacity may take more time to assess.