limeputty

Limeputty, or lime putty, is a traditional lime-based material used in masonry, plastering, and limewash. It is produced by slaking calcium oxide (quicklime) in water to form a creamy suspension of calcium hydroxide, which is then stored and aged to develop plasticity and workability. Properly aged lime putty remains workable for months, allowing it to be mixed with aggregates to create lime mortar or plaster.

The curing of lime putty occurs through carbonation, as carbon dioxide from the air reacts with calcium hydroxide to form calcium carbonate. This process is gradual, yielding a breathable, flexible finish that tolerates minor movement in masonry and helps reduce trap moisture and salt-related damage when used with porous substrates.

Common uses include traditional lime plaster, lime mortar for bricks and stone, and limewash bases. Limeputty is particularly favored in historic restoration because it is compatible with original materials and allows walls to breathe. It can be used with natural hydraulic lime (NHL) or pozzolanic additives to achieve different early-strength characteristics, but it remains distinct from cement-based mortars in its long-term behavior and moisture handling.

Modern practice often supplies pre-mixed lime putties or provides guidance for aging and mixing on site. Safety considerations include the caustic nature of fresh lime; appropriate protective equipment and ventilation are advised when handling lime putty. Limeputty remains a staple of traditional masonry and conservation work due to its compatibility, breathability, and ability to accommodate gradual movement in historic structures.