Lime putty is slaked lime in the form of a thick, butter-like paste. It is made by slaking quicklime with an excess of water and then letting the mixture mature under water for a long time. The longer the lime putty matures, the finer and creamier it becomes. It is the basis for traditional air-lime mortar and lime plaster.
Maturing under water
In making lime putty, the slaked lime is kept under a layer of water, sometimes for months or even years. During this maturing the lime particles grow ever finer and more even. A well-matured lime putty is creamy and easy to work, and gives a mortar or plaster with better adhesion, plasticity and fewer shrinkage cracks. Storing it under water stops the lime reacting with the air and hardening too soon.
Application
Lime putty is used above all in restoration and in craft plastering and masonry, where a soft, vapour-open and flexible mortar is valued. The worker mixes the putty with sand (and sometimes water) into laying or plastering mortar.
Points to note
- Work carefully and let the work dry slowly and sheltered
- Air lime, like ordinary lime, needs air and time to harden
Related terms
- Lime
- Slaked lime
- Lime mortar
- Binder
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