limewash

Limewash is a traditional decorative and protective coating for mineral substrates, made from slaked lime putty or hydrated lime mixed with water. It is often colored with natural pigments. Unlike modern acrylic paints, limewash is mineral-based and highly breathable, allowing vapor to pass through while resisting liquid water penetration. It can be used on interiors and exteriors, especially on porous materials such as lime plaster, brick, and calcareous stone.

Historically widespread in Europe and the Mediterranean, limewash has renewed interest in restoration and sustainable building due to its compatibility with historic masonry and its relatively low environmental impact. Application involves preparing a clean, damp surface and applying several thin coats with a brush or roller. The coating cures by carbonation rather than film formation, becoming harder over time while remaining somewhat soft and breathable. The finish is typically matte and chalky, with color provided by natural pigments.

Advantages include breathability, flexibility, easy repair, and low toxicity. Limewash minimizes moisture trapping and can contribute to improved indoor air quality. Disadvantages include limited water resistance, vulnerability to heavy rainfall during curing, potential efflorescence, and the need for periodic reapplication, often every 5–15 years depending on climate and exposure.

Safety considerations include the alkaline nature of lime, which can irritate skin and eyes; appropriate gloves and eye protection should be used. Environmentally, limewash has relatively low embodied energy, and the carbonation process absorbs CO2 over time, partially offsetting emissions.