Lime Paint
Sumpfkalk-based mineral wall paint for interior heritage and modern surfaces — vapour-permeable, naturally mould-resistant through high alkaline pH, suitable for humid rooms.
View product detailsMineral Surfaces · Solutions
Breathable Anti-Mould Systems
A Mumbai monsoon bathroom runs RH 80%+ for four months a year. A Bangalore north-facing apartment bedroom drops below indoor dew-point on July evenings. A Chennai basement carries chronic capillary rise from inadequately detailed footings. In all three rooms, the same wall keeps growing the same dark bloom no matter how many times it is repainted with conventional acrylic emulsion.
InteriorThree-Layer System4 compatible products
- Vapour-permeable — moisture moves through the finish, never trapped behind it
- Mumbai monsoon + Bangalore north-corner + Chennai basement documented
- Alkaline self-defending substrate (pH ~12 lime) or silicate mineral-bond
- Linseed-and-mineral system, no biocide leaching, no film-forming acrylic
Find your application
Pick the substrate. We'll show what fits.
Mumbai/Goa monsoon bathroom walls outside the shower stall — silicate-mineral default, lime alternative for low-spray walls.
4 compatible productsMineral Plaster Primer
Water-based silicate primer that evens absorbency on interior mineral walls — lime plaster, cement, clay, brick, aerated concrete, gypsum board. The prep coat under LEINOS lime, silicate, and natural mineral paints.
View product detailsDeep Sealer
The water-based deep-penetrating primer for absorbent interior wall substrates — saponified shellac and natural-resin soap flow into the pore network, the wax phase binds substrate dust, the topcoat lays down at uniform thickness and colour register. Solvent-free, plasticiser-free, very low VOC.
View product detailsSilicate Primer
Alkaline universal fixative for silicate and lime paint primers. Solvent-free, for interior walls and ceilings with uneven or highly absorbent surfaces.
View product detailsSystem & Substrates
Three-layer mineral wall system. Chemistry-matched primer + paint pair + optional third coat for opacity.
For non-moisture-stressed interior rooms, use the Interior Walls solution — full mineral palette without the ventilation-prerequisite framing.
The Coating System
Primer plus topcoat — the full chain.
Topcoat Options
Choose the finish character; the primer underneath stays the same.
Long-term Care
Extends the life of the finish over the years.
How This System Works
1
Primer
Wet-zone primer — Mineral Plaster Primer 622 is the canonical primer for the LIME family (Lime Paint 665) per gate 91. Water-based potassium silicate, silicification bond with the mineral substrate, vapour-permeable so the breathable anti-mould chemistry of the lime topcoat is preserved. Silicate Primer 621 is the clear-sister alternative for transparent prep on patched substrates. Deep Sealer 620 is the gate-91 primer for the OTHER family (natural-resin emulsion) and must NOT be used here under lime — primer-family mismatch causes adhesion failure and collapses the mineral-bond.
Mineral Plaster PrimerRecommended
Mineral Plaster Primer 622 — canonical primer under Lime Paint 665 (gate 91). Water-based potassium silicate, silicifies with the alkaline substrate, vapour-permeable (sd-value ~0.05 m). Whitish-pigmented for visual coverage check. 1 coat with brush, optional 5–10% water on extremely absorbent fresh lime plaster. Touch dry 6–12 h, lime topcoat 12 h+. The pairing is non-negotiable on lime-canon walls: lime paint over non-silicate primer delivers organic-paint behaviour, not mineral.
Silicate PrimerAlternative
Silicate Primer 621 — clear-sister silicate primer for transparent prep on patched substrates where 622's whitish pigment is unwanted (heritage register, glazed-in patches). Same potassium-silicate chemistry as 622, no pigment. 1 coat, dry 12 h before lime topcoat.
Deep SealerAlternative
Deep Sealer 620 — alternative ONLY for hybrid walls where the wall outside the lime zone is finished in Natural Resin Emulsion 660 (the emulsion-family primer). NEVER used under Lime Paint 665 — gate 91 primer-family split, mixing the wrong primer collapses the mineral-bond. Dilute 1:1 with cold water before application.
2
Base Coat
Lime Paint 665 is the breathable-anti-mould topcoat for shower-adjacent and low-spray bathroom walls — vapour-permeable, alkaline pH ~12 after cure (substrate-chemistry property that resists fresh colonisation under proper ventilation), soft chalky matte register. NOT for use inside the shower stall itself — that zone is tile or stone. 2 coats over Mineral Plaster Primer 622.
Lime PaintRecommended
Lime Paint 665 — vapour-permeable pure mineral lime paint with alkaline pH ~12 after cure. 2 coats diluted ~20% water with brush (NOT roller — roller leaves stipple that telegraphs through cure). Dry 4–6 h between coats, recoat 6–12 h. Carbonation cure 7–14 d normal / 21 d monsoon. Use on bathroom walls outside the direct shower-spray zone.
× 2 coats
3
Top Coat
OptionalOptional third coat of Lime Paint 665 — apply only when the second coat shows uneven cover after dry-back. Lime paint reaches full opacity slowly through carbonation; do not chase opacity wet, judge after dry under raking light.
Lime PaintAlternative
Optional third coat of Lime Paint 665 — applied only after the second coat has dried and the wall has been judged in raking light from a flashlight held flat against an adjacent surface. Same 20% dilution, same brush technique as coats 1 and 2.
Step by Step
How to Apply
Audit the ventilation BEFORE anything else
Mumbai and Goa bathroom mould is mostly a ventilation problem, not a finish problem. Most Indian bathrooms have a single exhaust fan used during 30% of shower-time — moisture stays in the room and condenses on cool walls overnight. Before specifying any finish, confirm: (1) exhaust fan is rated for the room volume and tested working; (2) the family agrees to run it during showers and for 20 minutes after; (3) at least one window or vent opens for cross-draught daily. If ventilation is failing, fix that first; no paint chemistry compensates.
Diagnose existing mould stains and substrate condition
If mould stains are visible: identify the source (leak / condensation / capillary rise). Scrape and sand the stained area mechanically back to sound substrate. Wipe with a 1:4 white-vinegar solution, let dwell 30 minutes, wipe with damp cloth, dry-back 48 hours. Test substrate moisture with a pin meter on at least 4 wall points — must read below 4% MC on masonry. If wet: identify the source (plumbing leak behind tile, missing weep hole at chajja, ground capillary) before the finish work begins.
Confirm wall chemistry and choose primer/paint pairing
Walls inside the direct shower-spray zone are tile or stone — no paint system in this brief belongs there. For shower-adjacent walls (the wet-but-not-sprayed half of an Indian bathroom): pair Silicate Primer 621 + Mineral Plaster Primer 622 silicate paint. For low-spray walls (vanity wall, towel-rail wall, ceiling): Mineral Plaster Primer 622 + Lime Paint 665 carries the alkaline substrate advantage at lower cost. Mixing primers across chemistries (e.g. 620 under 622 silicate paint) collapses the silicate mineral-bond — keep pairs intact.
Mask, scrape any old paint, sand
Mask all tile edges, the vanity counter, the mirror frame, and the door architrave. Scrape and sand any existing acrylic, latex, or oil paint back to sound mineral substrate — silicate and lime paints will NOT bond on top of acrylic films. Vacuum the surface and dust-cloth wipe.
Apply the chosen primer
For silicate paint route: stir Silicate Primer 621 well, apply 1 coat with a flat brush along the natural texture, dry 12 h. Cover plumbing fixtures during dry-back — silicate splash on chrome etches if not wiped immediately. For lime paint route: stir Deep Sealer 620, apply 1 coat with brush or roller, dry 4–6 h. Skip primer ONLY on a fresh, sound, moderately absorbent lime-plaster substrate (rare in Indian retrofit context).
Apply paint coat 1 (silicate 622 or lime 665)
For silicate (622): apply with brush in long even strokes — do not over-work. Coverage ~150 ml/m². Dry 6 h. For lime (665): dilute 20% with water, strain through a sieve, apply with a wide flat-brush (NOT roller — roller leaves stipple that telegraphs through cure). Dry 4–6 h. In both cases, run the bathroom exhaust fan during and 2 hours after application — your own paint cure benefits from ventilation just as the finished room will.
Apply paint coat 2 and decide on third
For silicate: recoat at 12 h, same technique as coat 1. For lime: recoat at 6–12 h, re-dilute if the bucket has thickened. After coat 2 has fully dried back (4 h minimum), inspect the wall in raking light from a flashlight held flat against an adjacent surface. If opacity is uneven or shadow telegraphs through, apply a third coat at the same dilution / recoat interval. DO NOT chase opacity while the paint is wet; mineral paints reach full opacity slowly through carbonation (lime) or silicification (silicate).
Cure and hand-back to ventilation routine
Light-use ready 24 h after the final coat. Full cure: 7–14 d for lime (extended to 21 d in 80%+ monsoon RH), 14–28 d for silicate mineral-bond. During the cure window, keep the exhaust fan running for 30 minutes after every shower; the chemistry needs the wall to dry between wet cycles. Wipe condensation drips off the wall with a microfibre cloth within the day during cure — pooled water on uncured lime paint leaves a darker patch. After cure, the maintenance routine is: ventilation discipline + monthly damp-wipe + annual visual inspection for stain reappearance (which points back to ventilation, not finish).
System Composition
- Ventilation audit FIRST — confirm the bathroom has working exhaust ventilation used during AND 20 minutes after every shower. Finish chemistry cannot compensate for trapped moisture from ventilation failure.
- Substrate moisture check — masonry must read below 4% MC on a pin meter before any primer goes on. Damp walls trap moisture behind the finish.
- Pre-treatment of any existing mould stains with mechanical removal (scrape + sand) plus a 1:4 vinegar wash, then full dry-back over 48 h before priming. The pre-treatment removes the stain; the finish chemistry creates a substrate inhospitable to fresh colonisation under proper ventilation.
- Silicate Primer 621 (1 coat, 12 h dry) — mandatory under Mineral Plaster Primer 622 on shower-adjacent walls. Deep Sealer 620 (1 coat, 4–6 h) is the alternative under Lime Paint 665 on low-spray walls.
- Topcoat: Mineral Plaster Primer 622 (silicate, 2 coats over 621) OR Lime Paint 665 (2 coats over 620). Third coat only when raking-light judgement after the second coat shows uneven cover.
- Excess wipe / brush-strap after every coat — pooled paint on bathroom walls cures slowly under monsoon RH and shows lap marks.
Why It Works
- Silicate Plaster Primer 622 over Silicate Primer 621 forms a mineral-to-mineral bond (silicification) with the substrate — the paint becomes part of the wall rather than a film on the wall. This bond is the chemistry behind the long re-paint cycle on properly-prepared masonry (7–10 years inland, 5–7 years coastal).
- Lime Paint 665 carries an alkaline pH of approximately 12 once cured — the high pH creates a substrate environment that is inhospitable to mould colonisation. This is a substrate-chemistry property, not a treatment claim: lime paint does not actively destroy anything; it presents conditions that fresh colonisation finds difficult under properly ventilated conditions.
- Both finish systems are vapour-permeable (sd-value ~0.01 m for lime, ~0.05 m for silicate) — moisture moves through the finish into and out of the substrate rather than condensing behind a vapour-impermeable film. On a poorly-ventilated wall, however, the moisture has nowhere to go even with a breathable finish; this is why ventilation is the load-bearing factor, not the chemistry.
- The Mumbai/Goa coastal monsoon documents a 30–50% reduction in expected service life over inland Bangalore/Pune — both salt-air UV on the exterior wall and continuous RH 80%+ for 4 months/year on the interior. Plan for shorter touch-up cycles in coastal context.
Pick the Right Build
Which build fits your surface?
Mumbai apartment bathroom shower-adjacent wall (silicate canon)
Standard 1990s-2010s Mumbai apartment bathroom with single small exhaust fan. Wall outside the shower stall, behind the vanity, behind the door. Silicate Primer 621 (1 coat, 12 h) + Mineral Plaster Primer 622 silicate paint (2 coats, recoat 12 h). MANDATORY: confirm with the family that the exhaust fan runs for 20 min after every shower — the finish only performs as documented under this ventilation discipline.
Silicate Primer 621 + Mineral Plaster Primer 622 — 2 coats
Goa villa heritage bathroom — low-spray walls (lime canon)
Older Goa villa bathroom on lime-plaster substrate with separate shower enclosure (tiled wet-zone). Walls outside the wet-zone: Deep Sealer 620 (1 coat, 4–6 h) + Lime Paint 665 (2–3 coats diluted 20%, recoat 6–12 h). The alkaline substrate matches the heritage register. Verify ventilation routes (often a tilting transom over the door in Goa villas — confirm it actually opens).
Mineral Plaster Primer 622 + Lime Paint 665 — 2–3 coats
Bangalore apartment guest bathroom — low-traffic shower-adjacent
Lightly used guest bathroom, no daily shower, condensation only from occasional use. Choose by aesthetic register: silicate 622 if the rest of the apartment carries a contemporary mineral palette; lime 665 if a softer matte chalky register suits the design. Both pair with their respective primer (621 or 620). Ventilation prerequisite still holds even at low use frequency.
Either: 621+622 OR 620+665 — 2 coats
Chennai bathroom with persistent re-blooming mould
Existing finish keeps failing within 6 months. This is a ventilation diagnosis, not a finish-spec problem. Do not respec until: (1) exhaust fan rated for room volume and confirmed running 20 min after every shower; (2) substrate moisture content below 4%; (3) no plumbing leak behind tile or wall (check with a moisture meter on suspect areas). If all three confirm, the spec is 621 + 622 silicate route — the silicate mineral-bond gives the best chance of holding. If even one diagnosis fails, the finish will fail again regardless of brand.
Diagnosis first; if cleared: 621 + 622 — 2 coats
What to Expect
- Light-use ready 24 h after the final coat. Full cure: 7–14 d for lime (up to 21 d in monsoon RH), 14–28 d for silicate. During cure, wipe condensation drips off the wall the same day; pooled water on uncured mineral paint leaves a darker patch.
- Lime paint develops a characteristic chalky matte register that is part of the finish, not a defect — slight cloud formations and colour variations are normal. Silicate paint reads slightly more uniform with a soft mineral matte.
- Re-coat cycle: 5–8 years inland on a properly-ventilated bathroom; 3–5 years on Mumbai/Goa coastal monsoon walls. Annual visual inspection for stain reappearance — fresh staining within 12 months points back to ventilation failure, not finish failure.
- NEITHER lime nor silicate paint is suitable for the inside of the shower stall itself — that zone is tile or stone. The chemistry covers the wet-but-not-sprayed surfaces only.
What to Avoid
- Finish is one of three factors — substrate quality + ventilation + finish chemistry. The finish chemistry CANNOT compensate for inadequate ventilation or wet substrate. Diagnose and fix those first.
- Not suitable for the direct shower-spray zone (the inside of a shower stall, the splash-back behind a bath spout) — use tile or stone in those zones.
- Not suitable on gypsum-board substrates in bathroom context — gypsum degrades under sustained moisture regardless of finish chemistry. Re-substrate with cement-board or lime-plaster before applying.
- Not compatible with prior acrylic, latex, oil, or polyurethane paint — mineral paints will not bond to organic films. Scrape and sand any prior film back to sound mineral substrate.
- Lime Paint 665 is highly alkaline during application (pH ~12) — wear protective gloves, splash-resistant eyewear, and protect plumbing chrome with masking. Causes serious eye damage and skin irritation; rinse splashes immediately.
- Wall Wax Finish 350 must NOT be applied over lime or silicate paint — it is only compatible with natural-resin-based paints and would block the breathable chemistry that the system depends on.
Scope & Limits
Where this system applies.
This solution covers three moisture-stressed Indian interior contexts: bathrooms outside the direct shower-spray zone, basements and low-airflow service rooms, and north-facing or monsoon-stressed residential walls. The substrate is sound mineral masonry — lime plaster, cement plaster, or mineral render — with structural waterproofing already in place.
Requirements
- Before compatible products can be reviewed, the following must be confirmed:
- Substrate moisture content reads below 4% MC on a pin meter across at least 4 wall points — if wet, find the source first
- Substrate is sound mineral masonry (lime plaster, cement plaster, mineral render) free from efflorescence and active salt migration
- Any structural waterproofing failure (capillary rise, lateral ingress, plumbing leak, roof drainage onto wall) is repaired and dry-back of 1–2 weeks is complete
- Working exhaust ventilation is provisioned for the room and the household has confirmed they will run it during and after moisture events (showers, cooking, washing)
- No remaining film of prior acrylic, latex, oil, polyurethane, distemper, or chalky whitewash — strip back to sound mineral substrate, mineral paints will not bond on organic films
Not compatible with
- Active leaks — untreated. Painting over a wet or leaking wall traps moisture behind the finish and accelerates failure. Repair the source, dry-back, then specify.
- Gypsum-board substrates in high-moisture rooms. Gypsum degrades under sustained moisture exposure regardless of finish chemistry. Re-substrate with cement-board or lime-plaster.
- Prior acrylic, latex, polyurethane, oil, or distemper films not stripped. Mineral paints (lime, silicate) bond chemically to mineral substrate only — applying over an organic film delivers organic-paint behaviour with mineral-paint cost.
- Exterior-grade products misapplied indoors. Mineral Plaster Primer 622 has an exterior-grade variant family with different additive balance — specify the interior-grade matched primer/paint pair for interior moisture-stressed rooms.
In the wild
Real surfaces. Real India.
Common Questions
Frequently Asked
- Honest answer: the chemistry helps; it does not stop colonisation on its own. Lime Paint 665 cured carries an alkaline pH of approximately 12, which creates a substrate condition that fresh mould finds difficult to colonise under properly ventilated conditions. Mineral Plaster Primer 622 silicate paint forms a vapour-permeable mineral-bond that prevents moisture entrapment. Neither finish actively destroys anything. In a bathroom with broken ventilation, a basement without exhaust airflow, or a wall with active leaks, staining will reappear regardless of finish chemistry. The system performs as documented only when paired with adequate ventilation and a structurally-sound substrate.
- Lime Paint 665 cures through carbonation — the calcium hydroxide in the wet paint reacts with atmospheric CO₂ to form calcium carbonate (the same mineral as natural limestone). The cured film carries a residual alkaline pH of approximately 12. This is a substrate-chemistry property, not a treatment claim: the paint does not contain added biocides or any other active treatment agents. The alkaline surface conditions are inhospitable to the moisture-and-organic-nutrient environment that mould colonisation needs to establish.
- Mineral Plaster Primer 622 silicate paint cures by silicification — the potassium-silicate binder reacts with the mineral substrate (lime plaster, cement, masonry) to form a permanent mineral-to-mineral bond. The cured film is the substrate, not a film on the substrate. Vapour-diffusion resistance is exceptionally low (sd-value ~0.05 m), allowing indoor humidity that condenses on a cool wall to evaporate back out through the finish rather than persist behind a vapour-impermeable acrylic film. This is the chemistry-level reason mineral paints outperform conventional emulsions on monsoon-stressed walls.
- Diagnose the partner conditions in this order: (1) is the substrate dry — pin-meter below 4% MC across multiple points? If wet, find the source: plumbing leak behind the wall, roof drainage failure overhead, capillary rise from inadequate plinth, lateral ingress from outside grade. (2) Is the ventilation working — exhaust fan rated for room volume and confirmed running 20 min after every shower or 30 min daily in basements? (3) Has the prior finish been fully stripped — any residual acrylic or distemper film blocks the mineral-bond. (4) Was the recommended primer/paint pairing used (621+622 for silicate, 620+665 for lime, no cross-pairing)? Stain reappearance within 12 months almost always traces back to one of these four — not to the chemistry itself.
- No. The direct shower-spray zone — the inside walls of a shower enclosure, the splash-back behind a bath spout — is tile or stone, not paint. Lime and silicate paints belong on the wet-but-not-sprayed surfaces: the vanity wall, the towel-rail wall, the ceiling, the wall behind the door. The chemistry handles condensation and ambient humidity; it does not handle continuous direct water spray.
- Conventional "bathroom paint" is typically an acrylic emulsion with a film-forming binder and added fungicides. The film is vapour-impermeable, which traps condensation behind the paint where it persists. The fungicides slow visible staining for the first 12–24 months, then leach out and the staining returns — often worse than before, because moisture has accumulated behind the film. Mineral systems (lime, silicate) work by the opposite logic: vapour-permeable film, alkaline or mineral-bonded substrate chemistry, no leaching biocides. Service life under proper ventilation is 5–10 years inland and 3–5 years coastal, with no biocide-leaching failure mode. Trade-off: mineral paints require chemistry-matched primers, careful substrate preparation, and the ventilation discipline this system depends on.
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