An introduction to lime - The Hempcrete Topic: Designing and Building with Hemp-lime - page 50

Traditional lime plasters, such as this lime putty plaster,
form vapour-permeable finishes. The surface is rubbed
back to 'open it up' and improve breathability (see page
240 ).
Mortars and plasters made from building lime are vapour permeable in their finished state,
which has important implications for the way the fabric of the building works: helping to
manage humidity within the structure and thereby keep the materials used to construct it in
good condition. Because lime is also hygroscopic, lime mortars and plasters help to 'buf-
fer' humidity levels in the building, which is also beneficial to the health of the occupants
(see Chapter 4, pages 56 and 58 ) .
Lime for building is produced from calcium carbonate (CaCO 3 ), found naturally in quar-
ried limestone, chalk, coral rocks or shell. The raw materials are burnt in a kiln, causing a