Obtained by calcining limestone (carbonate of lime), in a kiln, the heat drives off carbonic acid leaving a brittle white solid which is pure lime. Known as Quicklime and powerfully caustic; will combine readily with water and will slake, with great heat, to produce a hydrate of lime suitable for mortars or plastering. Properties will vary with the limestone (or chalk) found in different locations. Some will produce a non-hydraulic lime (needs presence of air to harden) or a hydraulic lime that will set and harden under damp conditions. (see Lime Mortars)