An introduction to lime - The Hempcrete Topic: Designing and Building with Hemp-lime - page 52

protective coating applied as a paint to lime renders and plasters. The desirable qualities of
lime putty improve with age, with the recommended minimum for production of a qual-
ity mortar being one-month-old putty; for plaster, the minimum is three-month-old putty.
Lime putty is commonly sold as six-month-aged as standard, and many examples exist of
lime putty being aged for many years under water and improving in quality and workab-
ility. The particular characteristics of any given lime putty will vary slightly according to
the raw materials used to produce it, the quality of the production and storage processes,
and how mature it is.
The processes of burning limestone and slaking quicklime, while traditionally undertaken
on a small, local scale, are impractical for most people and are dangerous if undertaken by
someone who does not know what they are doing. For those who wish to find out more
about these processes, we recommend contacting the UK Building Limes Forum.
Hydrated limes, owing to their carbonation through reaction with the air, are usually
known as 'air limes'. Other names for them are 'calcium lime' (CL), 'pure lime' or 'fat
lime' (although sometimes different names are used to refer to different qualities, e.g. a
mortar made from 'fat' - putty - lime being 'fatter' than one made from dry hydrate of
lime). They are sometimes also referred to as 'non-hydraulic limes' to distinguish them
from 'hydraulic limes' (see overleaf). Lime putties, and many products based on them,
such as limewash and ready-mixed plasters and mortars, are sold in the UK by specialist
suppliers of traditional or natural building materials, and their use has become increasingly
widespread over recent years.