Also known as putty lime or hydrated lime.
This is type of lime is often used in the restoration work of historical buildings and is often specified for buildings with listed status.
Fat lime products are produced using lime putty as the binder and are usually supplied as a wet mix. They take a long time to cure, but are the most breathable and most flexible lime products available. If kept in an airtight container and covered by a layer of water they will have a very long shelf life.
Lime putty is produced by adding quicklime to water. This process triggers an aggressive chemical reaction known as slaking. The putty is then put aside for a minimum of 4 months. This maturing process ensures that the slaking process is fully complete.
Mature lime putty is mixed with different grades of aggregates to produce traditional lime mortars, renders, plasters and fillers. It is also mixed with water to create Limewash.
Please Note: Fat Lime is often referred to as Non-Hydraulic Lime, which can be confusing as some people may think that this is the basis for the acronym NHL. However, NHL actually stands for Natural Hydraulic Lime, which is a different product with very different characteristics).