Gruntus – Deep-Penetrating Primer
Gruntus – Deep-Penetrating Primer
Gruntus is a clear, deep-penetrating primer that strengthens the substrate and locks down dust, getting walls ready for Limewash paint and decorative plasters.
- Soaks up to 5 mm into the surface, binding loose and crumbling layers together.
- Does not cover or change the colour of the wall – it dries completely invisible.
- Diluted 1:1 with water, so a single tin goes a long way.
- Vapour-permeable – the wall can still breathe.
- Free from heavy metals and aromatic solvents.
Technical data
| Dilution | 1:1 with water |
| Coverage | 14–18 m² per 1 L (once diluted) |
| Penetration depth | up to 5 mm |
| Application | brush or roller |
| Coats | 1, or 2 on very absorbent surfaces |
| Sizes | 1 L · 4 L · 10 L |
Why prime at all?
The most common painting problem looks harmless enough: you peel off the masking tape and a thin layer of wall comes away with it. That leaves a scar you have to fill and repaint.
It happens when the surface is dusty or slightly powdery – which describes most walls after sanding a skim coat, over old paint and on fresh gypsum plaster. The paint ends up gripping the dust rather than the wall.
Gruntus deals with the problem at its source. It penetrates the substrate, binds loose particles and creates a stable base. Afterwards the tape comes away cleanly, and every following coat bonds to the wall rather than to whatever was sitting on it.
How it differs from PrepCoat
| Gruntus | PrepCoat | |
|---|---|---|
| What it is | clear primer | white base coat |
| What it does | strengthens the wall, binds dust | evens out colour and absorbency |
| Does it cover? | no | yes, white-pigmented |
| When you need it | dusty, fragile or fresh walls | always before Limewash paint |
On a weak substrate you need both: Gruntus first to stabilise the wall, then PrepCoat so the colour comes out even.
Under thick decorative plasters such as Marmorinus and Romanus, Gruntus on its own is usually enough. Under paint and thin finishes you need both.
Where to use it
- gypsum skim coats and plasters, including fresh ones
- sanded, dusty walls
- old, powdery surfaces
- mineral substrates before decorative plaster
How to apply
- Clean the wall – remove dust, greasy marks and anything loose. Fill and level any defects before priming.
- Dilute 1:1 with water.
- Apply evenly with a brush or roller, without missing any patches.
- On very absorbent or heavily dusty surfaces, apply a second coat.
- Leave to dry completely before applying PrepCoat or plaster.