Building & renovation
How much fixative primer before painting?
Liters of fixative primer to even out suction on new plaster or chalky paint before finishing.
Quick answer
Fixative (or deep-penetrating sealer) balances suction so the first finish coat does not flash dry or leave holidays. One coat at 8–12 m²/L is typical on new plaster — we default to 10 m²/L. Worked example: 60 m² new walls, one coat, 10% waste → 60÷10×1.1 = 6.6 L → 3× 2.5 L or one 5 L + one 2.5 L.
Advanced settings
Paint needed
4.4 liters
- Cans to buy
- 2 × 2.5 L
Fixative primers even out suction on new plaster or chalky old paint — usually one coat at 8–12 m²/L. They are thinner than finish paint; do not skip if the wall drinks the first coat.
How it works
When you need it: new plaster / gypsum, sanded joint compound, chalky or dusty old paint, and walls that drink the first coat unevenly. When you can skip: already primed, uniform emulsion in good condition. Fixative is thinner than finish paint — roller or low-pressure spray. It is not a stain blocker (use a dedicated primer for nicotine/water stains) and not wallpaper size.
Typical order of work: clean → repair → fixative → finish coats. Pair with fixative primer sealer on bare gypsum or lime plaster before washable paint, then size litres of emulsion with the interior paint calculator.
Skipping it costs more than using it: the first finish coat dries patchy and you end up applying three coats instead of two, so the primer pays for itself with the tin you do not buy. The reason is that new plaster is not simply "absorbent" — it is uneven, and it is the unevenness that makes the patches. Two things to know before opening the tub: below 5–8 °C it does not film properly and stays powdery, so an unheated room in January is too cold even when it feels dry; and once dry it does not come off tiles or glass, so you mask before, not after.
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Frequently asked questions
Fixative on new plaster — mandatory?+
Strongly recommended on absorbent new plaster and after sanding joint compound — without it, the first finish coat soaks unevenly and you need an extra coat. On already-painted uniform walls, often skip.
Fixative vs bonding primer — same thing?+
Not always. Fixative / sealer mainly equalises suction on porous mineral walls. Bonding primers (aggrappante) grip glossy or difficult substrates. Read the label: some products do both; many do not.
Dilute fixative with water?+
Only if the label allows — many ready-to-use fixatives are sold pre-diluted. Over-thinning reduces sealing and you end up buying more finish paint to compensate.
How much for a 25 m² room?+
Floor area is not wall area — a 25 m² room often has ~55–65 m² of walls. At 10 m²/L one coat: ~6–7 L fixative before waste.
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