Technique N.02 — Calce Cruda
Romanus – Calce Cruda Effect
Romanus is a professional decorative clay plaster for an authentic Calce Cruda finish: a raw, living clay surface.
Technical information
Primer for decorative plasters
Romanus – Calce Cruda Effect
How the effect is created
About the material
Clay is one of the oldest building materials and one of the healthiest. It is fully natural, acoustic and antibacterial. Its greatest strength is the way it regulates the indoor climate: clay releases moisture into the air when a room is too dry and absorbs it when the air is too humid. So the wall does not just look natural – it actively makes the room more comfortable and healthier for the people in it.
Character of the effect
Calce Cruda is meant to be raw, imperfect and unfinished – and that is exactly its beauty. It does not chase perfect smoothness or repetition; its value lies in natural irregularity.
Once the second coat has dried, the material still looks alive: natural variations in 2–3 tones, typical of real clay, are visible (even more so up close). It is a one-of-a-kind, fully natural finish – one of the subtlest decorative effects you can create on a wall.
Application technique
- Primer for decorative plasters – apply with a roller or brush over the whole surface. Leave to dry for 6–8 hours before the first coat of Romanus.
- First coat of Romanus – apply with a Venetian trowel to the thickness of the plaster's grain. Leave to dry for 10–12 hours before the second coat.
- Second coat of Romanus – this is where the final Calce Cruda effect is decided.
The key to Calce Cruda is how you join sections in the second coat. Do not work in horizontal or vertical bands – make the joins deliberately irregular.
Load the Venetian trowel, then shade and spread the plaster to cover the previous clay layer. Apply it irregularly, pulling the material over the still-wet layer, joining and shading gently – the pressure on the trowel matters here too. For the next section, pick up more plaster, place it just ahead of the join and blend it irregularly into the previous one, keeping the natural, hand-made pattern of the texture. Small openings are deliberately left in the texture as you work; if one looks too large, reduce it straight away with a little more plaster. Bear in mind this only works one way – once an opening is closed, it cannot be reopened.
Keep refreshing the joins as you go – do not work in squares or large areas, but in passes the width of the trowel. This keeps the joins invisible, although the final result also depends on your experience with the material. Shade over a width of approx. 10–15 cm, working into the still-wet plaster.
The second coat takes 24 hours to dry fully (at 20 °C and 75% humidity). It may take longer depending on how thickly the plaster was applied.
Application tips
On very absorbent surfaces (such as cement-lime plaster) the primer is easier to apply with a brush.
Apply the first coat to the thickness of the Romanus grain. Once a section of, say, 1–2 m² is done, do not go back to “improve” it – half-wet plaster is very easy to spoil.
Please note: this is a natural product and it is very sensitive to water – contact with water can change its colour.
Protecting the plaster
We do not recommend sealing this product.
You are applying a material that breathes, is natural and regulates the room's climate. Closing it under a sealer defeats the reason for choosing an ecological material in the first place. We want the wall to breathe and the clay to balance humidity freely.
There is a very practical side to this too: if an unsealed wall is damaged, a section can be repaired (especially in light colours). Once a wall is sealed, a repair means sanding off the whole sealer coat with a dust-extracting sander – a costly job that many contractors are reluctant to take on.