Primer isn’t always necessary, such as when you’re recoating walls and trim that are in good condition and were previously covered in a similar shade and formulation. But with new drywall and fresh plaster, primer is essential to seal the surface. If you’re applying a light color over a dark one, the previous paint job is damaged or deteriorated, or you’re coating a porous or slick surface, using an appropriate primer will ensure optimal coverage.
Here are our recommendations for common surfaces:
- Walls: A general purpose, water-based, 100% latex formula should do the trick here. If you’re making a big color change, ask your paint store to tint the primer to ensure even coverage.
- Bare wood trim: Henrique relies on oil-based primer for this: “It fills and seals the pores so that whatever paint you use will adhere well.”
- Painted wood trim: For trim previously painted with latex, a water-based latex primer is fine. But if you’re unsure what type of paint was used, you may want to use one that’s oil-based.
- Clear-coated wood trim: If the trim has a coat of polyurethane or varnish, shellac primer will provide the best adhesion. Since both oil-based and shellac primers give off volatile organic compounds (VOCs), which can damage your lungs, be sure to work in a well-ventilated space.
- MDF: For medium-density fiberboard moldings or built-ins, choose shellac- or oil-based primer. Water-based formulas can cause the material to swell and crumble.
- Masonry: Got an exposed brick wall or chimney indoors? Seal the pores with a water-based latex primer.
- Metal: Use an oil-based primer on ferrous metals that contain iron to prevent rust and a water-based latex metal primer on nonferrous surfaces.
- Plastic: If you’re painting laminate, go with a bonding primer, a modified acrylic formulation made to adhere to slick surfaces.