This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Lime is now manufactured in nearly all parts of the country, but differs in character in different localities. In using a lime which is not already familiar, some inquiry should be made as to its properties, especially if used for plastering. Good lime in general should be free from cinders or clinkers, and with less than 10 per cent of impurities, and should be found in large lumps which will slake readily in water, making a soft paste, free from residue or "core." It should further completely dissolve in soft water. Slaked lime, or "lime-putty," as it is commonly called, will keep indefinitely if protected from the air so that it does not dry up. This is usually done by covering it with sand in the bed in which it is slaked. Lime, before slaking, will absorb moisture from the air and become "air-slaked;" this destroys its strength and care should be taken that all lime is carefully protected from dampness until used.
Lime mortar does not possess the "setting" quality of cement, but gradually hardens by exposure to the air. Lime mortar does not harden under water or in very damp situations, but in dry places where there is ample exposure to the atmosphere, it will set hard enough for all ordinary uses of brickwork, except arches and piers, and where excessive loads may be applied.