Naturally Mould-Resistant Paint

KEIM mineral paints are naturally mould-resistant because of how they work and what they’re made from:

1. Highly alkaline: Fresh mineral paint has a high pH, which creates an environment where mould and mildew simply don’t like to grow.

2. Silicate (mineral) based: There are no organic binders for mould to feed on (unlike acrylic or vinyl paints).

3. Extremely breathable: KEIM allows moisture vapour to pass through the wall instead of trapping it, which dramatically reduces condensation — one of the main causes of mould.

4. No added biocides needed: The resistance is inherent, not reliant on chemical additives that can wear off over time.

With all that said (and this is the important caveat):

No paint can stop mould if the substrate stays wet.

If you’ve got ongoing moisture issues (leaks, rising damp, poor ventilation) mould can still form on surface dirt or dust sitting on top of the paint. But it’s not feeding on the mineral paint itself.

Benefits of Biocide free

This comes up a lot, especially with mineral paints and healthier building conversations.

People don’t avoid biocides because they’re useless — they avoid them because of what they cost over time.

Why people don’t want biocides

1. They wash out (and then stop working)

Biocides are sacrificial. Moisture, cleaning, UV and weather slowly leach them out of the paint film.

→ Once they’re gone, the mould protection is gone too.

2. Environmental impact

Washed-out biocides end up in:

    •    Stormwater

    •    Soil

    •    Rivers and waterways

They’re designed to kill organisms — so they don’t exactly stop being toxic once they leave the wall.

3. Health concerns (especially indoors)

Some people are sensitive to biocides and preservatives, which can:

    •    Trigger headaches or respiratory irritation

    •    Off-gas in interiors

    •    Be an issue in schools, healthcare, and residential spaces

Even “low-VOC” paints can still rely heavily on biocides.

4. False sense of security

Biocides can mask moisture problems instead of fixing them.

If condensation or damp is present, mould will return as soon as the biocide is depleted.

Benefits of biocide-free systems (like mineral paints)

1. Long-term mould resistance

Biocide-free doesn’t mean unprotected — it means:

    •    High alkalinity

    •    No organic food source

    •    High vapour permeability

These properties don’t wash out or degrade over time.

2. Healthier indoor environments

    •    No toxic additives

    •    No off-gassing

    •    Ideal for asthma-sensitive or chemically sensitive occupants

3. Environmentally responsible

    •    Nothing leaching into waterways

    •    Better for dense urban areas and heritage zones

    •    Aligns with sustainable building standards

4. Performance instead of chemistry

The system works because of physics and chemistry of the substrate, not because something is added to kill life.

5. Transparency & honesty

If mould appears on a biocide-free surface, it’s a clear signal of a moisture issue — not a hidden failure.

Biocides work by killing mould temporarily. Mineral paints prevent mould by removing the conditions mould needs to survive, permanently.