suolalaastia

Suolalaasti, or salt plaster, is a traditional plaster material historically used in Finland and other Nordic regions. It denotes plaster mixes in which salt is included as an additive within the binder, most commonly lime or gypsum, sometimes with cement or lime putty. Exact recipes varied by region and era, but salt was deliberately incorporated to influence the plaster’s properties and workability.

Typical formulations combine lime-based or gypsum-based binders with sand or other aggregate, and salt is added during preparation. Sea salt or rock salt may be used, in varying amounts. The mixture is prepared, applied in coats to prepared surfaces, and finished with smoothing or decorative techniques. In some crafts, suolalaasti was used for interior walls, panels, or decorative reliefs.

Advantages of suolalaasti included its simplicity and low cost, making it accessible in traditional building and crafts. However, higher salt content can lead to efflorescence, moisture-related deterioration, and potential weakening of the plaster over time. Salt can also affect adjacent materials and finishes, and its suitability diminishes in damp or modern structural contexts without careful design and treatment.

Today suolalaasti is mainly of historical interest and is studied in traditional building practices and restoration efforts. Some artisans and conservators experiment with salt plaster for decorative surfaces or art projects, often with controlled formulations and modern stabilization techniques to manage durability and moisture.