Hairline cracks in the plaster before painting? Silicate paint will highlight them. This filler primer bridges the cracks and evens out absorption. Breathable (V1), yet rain-resistant (W3). This is the filler primer of the Biocalce silicate system.
-
Hairline-cracked, uneven substrate: fills and bridges — optimal crack bridging, silicate paint does not highlight cracks
-
Part of the system: the filler primer of the Biocalce silicate system — applied above Biocalce Silicato Consolidante, beneath the silicate paint
-
Facade exposed to rain: breathable and rain-resistant — V1 vapor permeability and W3 low water absorption (EN 1062-3) simultaneously, the wall stays dry
-
Risk of blotchy painting: evens out absorption — uniform shade beneath the silicate surface, no blotchiness shows through
-
Optimal vapor/water balance: DIN 18550 (Künzle) — w < 0.5 kg/m²·h⁰·⁵ and Sd < 2 m, the wall breathes, does not absorb rain
-
Cleaner facade: bacterium- and fungus-repellent effect (CSTB method) — less biological contamination
-
Primer, not final coat: the color and decorative surface are provided by the Biocalce Silicato Puro Pittura or Biocalce Silicato Puro silicate layer
| Type |
Silicate filler / crack-bridging primer (exterior and interior) |
| Binder |
Pure potassium silicate (DIN 18363) |
| Performance |
V1 vapor permeability
W3 water resistance (EN 1062-3) |
| Material requirement |
≈ 0.15–0.25 l/m² per coat
4 l ≈ 15–25 m², 14 l ≈ 55–90 m² |
| Packaging |
Bucket 4 l and 14 l |
| Storage |
≈ 6 months |
What is it suitable for?
Substrates: Mineral surfaces — new, matured, and old plasters, brick, well-adhering masonry materials, partially renovated surfaces, porous materials with varying absorption, as well as mineral substrates of KlimaExpert thermal insulation systems. Suitable for slightly uneven, hairline-cracked surfaces.
Spaces: Exterior and interior — primarily facades and external surfaces where crack bridging and uniform absorption are required before silicate painting.
Function in the system: The filler and crack-bridging primer of the Biocalce silicate system. Applied above the consolidating primer and beneath the silicate surface.
Not suitable for:
- As a standalone, finished surface (without silicate paint) — this is a primer, not a decorative layer
- On damp, unseasoned substrates
- On contaminated, loose, dusty surfaces
- On old paint or decorative whitewash
- On gypsum-based substrates
- For walls exposed to capillary moisture — first a moisture-proof plaster (Biocalce Zoccolatura / Benesserebio) is needed
The Biocalce silicate system
Biocalce Silicato Fondo is the filling, crack-bridging primer of the silicate system. The possible breathable build-up:
Not every primer is always necessary — the condition of the substrate decides. Silicato Fondo fills and bridges uneven, hairline-cracked surfaces before silicate painting. On dusty, weak, crumbling substrates, first strengthen with Biocalce Silicato Consolidante; on sound, solid substrates, Silicato Fondo can be applied directly. On smooth, even surfaces, the fine Biocalce Silicato Fondo Fino is sufficient. The exact layering is specified by the substrate and the Kerakoll system description.
Which silicate primer is needed?
-
Strengthening dusty, weak, crumbling substrate: Biocalce Silicato Consolidante — deeply strengthens
-
Uneven substrate + crack bridging: Biocalce Silicato Fondo — this product fills and bridges, W3 rain-resistant
-
Fine, even absorption without damaging the surface: Biocalce Silicato Fondo Fino — thin, leveling
Frequently Asked Questions (FAQ)
What should I do about hairline cracks in the plaster before painting?
Apply a filling, crack-bridging silicate primer. It bridges hairline cracks so the silicate paint does not show them through. The surface remains even.
Which silicate primer is needed for facades?
For uneven, hairline-cracked facades, use the filling Silicato Fondo. It breathes (V1) and is rainproof (W3), keeping the wall dry. On dusty substrates, first consolidate with Biocalce Silicato Consolidante.
What do V1 and W3 mean?
V1 means high vapor permeability — the wall lets moisture escape. W3 means low water absorption — it does not absorb rain. Together they keep the facade dry.
Is a consolidating primer needed under Silicato Fondo?
On dusty or weak substrates, yes: first Biocalce Silicato Consolidante consolidates the surface. On sound, solid substrates, Silicato Fondo can be applied directly.
Is a topcoat needed over the filling primer?
Yes. Silicato Fondo is a primer, not a finished surface. On top goes the Biocalce Silicato Puro Pittura silicate paint or the Biocalce Silicato Puro noble plaster.
How much primer is needed, how many m² does it cover?
Approximately 0.15–0.25 l/m² per coat. The 4-liter covers about 15–25 m², the 14-liter about 55–90 m². The exact amount depends on the substrate.
Is lime or silicate primer needed?
The decorative surface decides. For silicate painting (Biocalce Silicato Puro Pittura), a silicate primer is needed — this product belongs to that system. For lime painting or lime noble plaster (Biocalce Tinteggio, Biocalce Marmorino), a lime primer is required: Biocalce Fondo or Biocalce Fondo Universale.
When should I not use it?
Do not apply on wet, dusty, or dirty substrates, gypsum, or old paint. Also not on walls with rising damp — those require a moisture-proof plaster first.
Can it be purchased separately?
Yes. You can purchase it even if you already have the other system products, if you are repairing an existing surface, or if you have a small leftover from a project.
Can I apply it myself?
Yes — with a brush or wool roller, in one or two coats. Exterior work requires scaffolding and practice. We also carry out the complete silicate system.
