① New Plaster / Concrete
Extremely porous and alkaline. Without primer the wall absorbs the resin unevenly, causing shadows and future peeling. Primer is absolutely mandatory.
Interior Primers: When Are They Needed
In the world of renovation there's a golden rule: a perfect paint job is 80 % preparation and 20 % paint application. At the heart of that preparation sits the primer - the "unsung hero" of every painting project. It doesn't carry the pigments of the topcoat, but contains specialised resins that create the perfect bonding bridge between wall and paint while sealing the pores.
Primer by Surface Type
The material you're painting over dictates whether primer is needed - and which type. Here are the five most common scenarios:
② Plasterboard (Drywall)
A double trap: paper (absorbent) + jointing compound (even more absorbent). Without primer, joints "flash" through the paint. A water-based acrylic primer unifies the surface.
③ Old Painted Wall
Nicotine, moisture or marker stains? You need a stain-blocker. If the wall is "chalking" (leaving powder on your hand), use a high-penetration primer to stabilise it.
④ Oil-Based Paint
Water-based emulsion won't grip glossy oil paint - it peels off like a film. Solution: sand the surface + apply an adhesion primer (Universal Primer).
⑤ Textured / Relief Walls
The textured surface traps dust and grime. After thorough cleaning, a micronised acrylic primer stabilises the peaks and seals micro-cracks.
Primer Categories: What to Ask For
At the paint store you'll find three main primer families. Your choice depends on the type of problem:
Water-Based Acrylic (Micronized / Latex)
The most popular for interiors. Odourless, dries in 1–2 hours, ideal for new plaster and plasterboard.
Solvent-Based (Spirit-Based)
Penetrate deeper. Best for crumbling surfaces or old limewash/wallpaper glue residues. Strong odour - good ventilation is essential.
Specialty / Hybrid
Stain-blockers: lock in smoke and yellowing (often shellac-based). Bonding Primers: grip glossy surfaces (tiles, melamine, oil paints).
When You Can Skip Primer
It's not always mandatory. You can skip primer if all of the following apply:
✓ Already painted wall
The wall has a standard matte or satin emulsion/acrylic paint in good condition.
✓ Clean surface
No peeling, stains, mould or dust.
✓ No patching
No filler repairs that leave bare compound exposed.
✓ Similar shade
The new colour is the same as or darker than the old one.
Self-Priming paints (paint + primer in one) save time on walls in fair condition, but they can't replace a dedicated primer on bare plasterboard, heavy stains or oil-based coatings.
The Primer Selection Algorithm
Follow these three steps to always find the right solution:
Step 1: Is the surface bare?
Plaster / Concrete / Filler → micronised acrylic primer. Plasterboard → specialist drywall primer (latex). If already painted, go to Step 2.
Step 2: What condition is the wall in?
Stains (smoke, moisture) → Stain-blocker primer. Chalking / crumbling → solvent-based primer. If stable, go to Step 3.
Step 3: What paint was underneath?
Glossy oil / enamel → Adhesion Primer (Universal). Standard matte/satin emulsion → no primer needed - proceed to painting!
Conclusion
Primer isn't an "extra coat" - it's insurance for your investment. A tin of quality primer costs far less than the multiple coats of expensive topcoat you'd need without it. Diagnose your wall, follow the algorithm, and the result will reward you with long-lasting durability.
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Painting New Plaster or Plasterboard Painting Over Old Oil Paint Primers: When Are They Really Necessary?
Interior Paints
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