How do I paint over old gloss paint?
Why paint slides off gloss, the abrade-and-degrease routine that works, and when an adhesion primer earns its place.
- Difficulty
- beginner
- Time
- 1 hr
- Read
- 3 min
- Safety
- caution
Short answer
Wash it, abrade the whole surface until the sheen has gone completely, wash the dust off, and prime. The new paint needs a mechanical key and a clean surface — the shine itself is what it cannot stick to. Where sanding is impractical, a proper adhesion primer does the same job chemically.
Old gloss is hard, non-porous and shiny, which is three separate problems for adhesion. Every reliable method for painting over it addresses all three.
Safety
What you'll need
- sugar soap or degreaser
- 120 to 180 grit abrasive
- adhesion or bonding primer
- filler (optional)
- dust sheets and masks
Step by step
- Check for lead paint first.Anything painted before about 1980 may contain lead. Test with a kit and, if positive, use wet abrading and avoid heat.
- Wash the surface thoroughly.Sugar soap or a degreaser, then rinse with clean water. Kitchen and bathroom woodwork carries a film of cooking grease and body oils that defeats any primer.
- Abrade until the sheen is gone.One-twenty to one-eighty grit over every surface. This is the step that matters most, and partial sanding leaves shiny patches where the new paint will peel.
- Do not skip the awkward areas.Mouldings, panel corners and beading are exactly where paint lifts first because they are the hardest to abrade. Use an abrasive sponge or a folded sheet.
- Repair the surface.Fill chips and dents, and sand the fillings flush. Gloss shows every defect, and gloss over gloss shows them twice.
- Remove all the dust.Vacuum, then wipe with a slightly damp cloth or a tack cloth. Dust under a primer is a release layer.
- Apply an adhesion primer.A bonding primer designed for glossy and difficult surfaces. It is what makes water-based paint over old oil-based gloss reliable rather than hopeful.
- Let the primer cure properly.Follow the stated recoat time rather than the touch-dry time. Priming and topcoating too quickly is a common cause of a soft finish.
- Apply thin topcoats.Two thin coats rather than one heavy one. Thick coats on a non-absorbent surface sag and take far longer to harden.
- Sand lightly between coats.A light key with fine abrasive between coats removes any nibs and improves adhesion between layers.
- Consider stripping instead where the paint is thick.Where mouldings have lost their detail under many layers, chemical stripping gives a far better result than another coat over the top.
Tips
- The shine is the enemy. If you can still see a sheen after sanding, keep sanding.
- Test for lead before dry sanding anything painted before 1980.
- An adhesion primer is not a substitute for cleaning and abrading, but with them it makes the job reliable.
Common mistakes
- Painting straight over gloss with no preparation — There is no key and no porosity. The new paint sits on top of the old and peels off in sheets at the first knock, often taking a large area with it.
- Cleaning after sanding rather than before — Sanding grinds surface grease into the abraded surface. Degrease first, then abrade, then remove the dust.
If it doesn't work
New paint peeling off in sheets
Cause: No key or a greasy surface underneath — Fix: Strip the failed paint, wash with degreaser, abrade thoroughly, prime with an adhesion primer and repaint.
Paint lifting only around mouldings
Cause: Those areas never got abraded — Fix: Sand the detail properly with an abrasive sponge, prime and recoat those sections.
Finish looks lumpy and every defect shows
Cause: Old chips and runs not filled and flattened — Fix: Sand flat, fill, sand again, and recoat. Gloss magnifies every imperfection.
Topcoat stayed soft for weeks
Cause: Applied too thickly on a non-absorbent surface, or over uncured primer — Fix: Allow full curing time between coats and apply thinner coats. Very soft films may need removing.
Questions people ask
Do liquid sanders work?
Deglossing liquids soften and dull the surface chemically and can help where sanding is impractical, such as intricate mouldings. They are less reliable than abrading and usually still want a bonding primer over them.
Can I use emulsion over gloss?
Not directly and not durably. With a proper adhesion primer it is possible, but a paint designed for woodwork will wear far better on a surface that gets touched.
How do I know when I have sanded enough?
Look at the surface at a low angle towards a light source. Any remaining shine is a spot the new paint will not grip.