Solutions
Walls that let moisture move back out instead of holding it in.
Validated by
Sd ≈ 0.01·pH ≈ 13·Class 1·VOC < 1 g/l
The pain — diagnosed
In Mumbai by September, the bathroom ceiling has grey-black spots again. The north bedroom smells of damp cotton. The emulsion bought last spring is lifting at the skirting. The wall is not the problem — the sealed film on top of it is.
What the substrate endures
Monsoon humidity
Weeks of 85%+ indoor humidity, with bathrooms and kitchens adding steam daily. Ventilation cannot keep up; the wall absorbs what the air cannot hold.
Vapour drive
Moisture inside masonry moves toward the room surface. A sealed acrylic film pushes it back — it condenses behind the paint instead of leaving.
Cold corners
North-facing walls and shaded corners sit below dew point for hours a day in the wet season. A permanently damp paint surface is where colonies start.
Organic film
Acrylic binder and thickeners are organic matter. Once the in-film biocide depletes, the coating itself can feed the colony it was meant to prevent.
Emulsion paint dries to a continuous polymer film — a vapour barrier in exactly the wrong place. Moisture migrating out of the masonry condenses behind the paint; the bond weakens; blisters and peeling follow. The permanently damp, organic surface layer gives mould its foothold — and a stronger biocide changes the timetable, not the mechanism.
The cycle
bleach → repaint → re-bloom. Another sealed film every cycle; a damper wall every year.
The mechanism
Mechanism · 01
Slaked lime cures at pH ≈ 13 (per TDS) — alkalinity that is naturally hostile to mould spores on the wall surface. The manufacturer describes the cured paint as antibacterial and mould-resistant. The protection is the mineral chemistry itself: nothing is added, so nothing depletes or leaches.
Mechanism · 02
The 622 + 665 system stays open-pored after curing — vapour resistance Sd ≈ 0.01 per TDS, effectively open. Moisture in the masonry keeps moving out through the surface into the room air, where ventilation carries it away instead of it being held behind a sealed film.
Mechanism · 03
665 bonds chemically with mineral substrates — the TDS calls it silicifying: the lime coat and the plaster become one mineral layer, with no film-to-wall bond line to fail. Where old walls are pitted, the 683 lime filler — itself high-pH and formulated for damp and mould-prone rooms — rebuilds a sound mineral base first.
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 productA matured lime-putty mineral wall paint for interior heritage and modern surfaces — highly vapour-permeable; its high alkaline pH makes the surface antibacterial and well suited to mould prevention and remediation in damp rooms.
View productNatural-resin emulsion wall paint for modern Indian interiors — washable Class 3, vapour-permeable Class 1, solvent-free. The natural-chemistry alternative to acrylic emulsion.
View productThe everyday natural-resin interior white wall paint for residential and commercial fit-outs. Washable Class 3, vapour-permeable Class 1, solvent-free.
View productApplication
Strip loose and flaking emulsion back to sound mineral plaster and remove any sinter skin mechanically (per TDS). Lime bonds to absorbent mineral substrates — the wall must be clean, dry, sound, and free from efflorescence before anything else happens.
Fill holes and level damaged zones with 683 lime filler in 1–3 mm lifts. Prime chalking or very absorbent surfaces with 622 mineral plaster primer — recoatable after about 12 hours (per TDS).
Apply 665 evenly with a wide brush, working in all directions, every coat diluted with up to 20% water. Depending on substrate, 2–3 coats, recoatable after about 24 hours at 20 °C — full hiding power arrives only as the paint dries (per TDS).
The finished surface is matt, recoatable, and vapour-open. New base plasters must be at least 2–3 weeks old before painting; pre-wet strongly absorbent old lime coats (per TDS). Ventilate humid rooms normally — moisture now passes through the surface instead of collecting behind a film.
Per-product TDS sheets are the authoritative source for coverage, drying intervals, and tool selection. Use these steps as the system-level shape, then download the relevant TDS from each product page.
Lab evidence
Independent labs, named standards, batch-traceable certificates.
Vapour-open lime (665)
Alkaline lime chemistry (665)
DIN EN ISO 7783-2 (650/660)
Lime Paint 665, per TDS
Compare
Conventional path
What fails
The film seals the wall; vapour condenses behind it; blisters lift the paint. The in-film biocide depletes within a repaint cycle or two — and mould re-colonises the permanently damp film surface.
With LEINOS instead
Why it holds
622 + 665 lime system — open-pored (Sd ≈ 0.01) and alkaline (pH ≈ 13) per TDS: the surface stays vapour-open and mineral, with no added biocide to deplete.
Conventional path
What fails
Bleach clears the visible colony, not the damp film surface that grew it. The next monsoon brings the bloom back — often straight through the fresh coat.
With LEINOS instead
Why it holds
Strip the film once, rebuild with 683 where needed, prime with 622, finish with 665 — high-pH mineral chemistry the manufacturer describes as well suited to mould prevention and remediation.
Conventional path
What fails
Not visibly mouldy — just musty. Vapour-tight paint keeps interior walls from releasing daily steam loads, so humidity condenses in cold corners and behind furniture.
With LEINOS instead
Why it holds
650 / 660 natural-resin emulsions — vapour-permeability Class 1 (DIN EN ISO 7783-2, per TDS): interior walls that keep drying outward through the whole monsoon.
Specifier questions
The acrylic film traps monsoon vapour against the wall. Moisture rising from the substrate cannot escape outward, condenses behind the paint, lifts the bond, and creates blisters. Biocides in the paint buy a season or two before mould re-colonises. The fix is to remove the film and switch to an open-pored mineral system — 622 primer + 665 lime — so vapour exits through the wall surface instead of being trapped.
Yes — slaked lime (calcium hydroxide) cures at pH ≈ 13, alkaline enough to suppress mould-spore germination on the wall surface. The manufacturer describes the paint as antibacterial and well suited to mould prevention and remediation — the protection is the lime chemistry itself, not an added biocide. (Not a tested antimicrobial specification; we make no such claim.) No biocides, no preservatives are added.
No — lime paint bonds chemically with mineral substrates (lime plaster, render, concrete, brick) through carbonation. It will not bond reliably to an acrylic film. The existing emulsion must be removed mechanically, the substrate exposed and consolidated, then 622 mineral primer applied before 665. Where stripping leaves the plaster pitted, the 683 lime filler rebuilds a smooth mineral surface first — it is formulated for wall preparation in damp and mould-prone rooms. Specifier notes are in each product TDS.
