Gear · CSL–G13

Primers and stain blockers

Illustration of primer cans with a paint roller and brush
Short answer: Use primer for stains, bare surfaces, glossy finishes and big color changes. Water-based primers suit most walls; oil-based and shellac primers are for stubborn stains and odors.

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Primer does three jobs: it helps paint stick, it seals porous surfaces so paint dries evenly, and it blocks stains from bleeding through. You do not always need it, but the situations where you do are predictable.

Always follow the manufacturer's label for ventilation, drying times and compatible topcoats. Oil-based and shellac primers have stronger fumes, so wear a respirator and ventilate; see our safety page.

Water-based multipurpose primers

Who it is for: most interior walls and trim.

These are low-odor and clean up with water.

Stain-blocking primers

Who it is for: water stains, smoke, marker and tannin bleed.

Oil-based and shellac primers block stubborn stains.

Specialty primers

Who it is for: damaged surfaces and damp rooms.

Sealers firm up chalky or damaged surfaces; mold-resistant coatings suit bathrooms.

Tools for priming

Who it is for: anyone priming walls.

Use cheaper brushes and covers for primer so you do not clog good ones.

Surface prep before primer

Who it is for: any surface with dirt, grease or gloss.

Primer does not replace cleaning and sanding.

FAQ

Do I always need primer?
No. Clean, sound, previously painted walls with a similar color often do not need it, while stains, new drywall and glossy surfaces usually do.
Can I tint primer?
Many primers can be tinted to a gray shade close to your topcoat, which can improve coverage with deep colors. Ask the retailer or check the label.
Is paint-and-primer in one the same as primer?
It combines both functions in one product, but it is not a substitute for dedicated stain-blocking primer in problem areas.
How long should primer dry before painting?
Follow the product label because times vary by primer type and conditions.

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