Mineral silicate paint is a coating applied to masonry, concrete or render (the Dutch verb is “keimen”). Unlike ordinary paint it does not sit on the wall as a loose film but bonds chemically with the substrate. The binder — liquid potassium silicate (water glass) — reacts with the mineral components of the substrate, a process called silicification. The technique is widely known by the German brand Keim.
How it works and its advantages
Because the paint bonds through silicification rather than forming a closed film, the result is a very durable, vapour-open finish:
- Vapour-open — water vapour can escape through the coating, so the paint does not blister or peel.
- Strong bond — the paint fuses with the stone instead of lying loosely on it.
- Water-repellent yet breathable — rainwater does not penetrate, but the wall keeps breathing; this limits damp, mould and moss.
- Colour-fast — the inorganic pigments are highly colour- and UV-stable.
- Matt, lime-like appearance — suited to historic and mineral facades.
Application
- Facade renovation — over brick, sand-lime brick, concrete and existing mineral render.
- Monuments — valued because the vapour-open behaviour suits old, damp-sensitive walls.
Points to watch
- The substrate must be mineral, clean and sound; silicate paint does not bond well over an old, closed plastic or emulsion layer.
- Do not work in full sun, in frost or on a wet substrate.
- Budget roughly €25 to €50 per square metre for painting a facade this way, including preparation and labour; the price depends on the condition of the substrate.
Checks before applying mineral silicate paint
- Substrate is mineral, clean and sound: Silicate paint needs a mineral, clean and sound substrate to bond.
- No old closed plastic or emulsion layer: Silicate paint does not bond well over such a layer.
- No full sun, frost or wet substrate: Do not work in these conditions.
Related terms
- Facade rendering
- Facade renovation
- Lime
- Air lime
- Breathing
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