Some of the common question we get asked about lime are shown below. If your question wasn't listed above then please contact us and we will do our best to help you
What is lime and why use it?
Lime is made by burning limestone to produce quicklime which is then slaked with water. The resulting putty or powder is mixed with sand to make mortars, renders and plasters. The plasticity of lime, its compatibility with stone and brick, the simple technology of its production and the ready availability of the raw materials (limestone, chalk, marble, coral and shell) has made it an essential and valued material for traditional building throughout the world.
What is the difference between putty lime and hydraulic lime?
Putty lime is made from high calcium raw materials like pure limestone, chalk and shell. It only hardens by reaction with carbon dioxide in the air. Putty lime and putty lime mortars can be stored indefinitely in airtight conditions. Hydraulic lime is made form clay bearing limestones which make a type of lime which sets by reaction with water. Hydraulic limes have higher compressive strengths than putty lime and harden more quickly.
What are the benefits of lime compared with cement?
Portland cement based mortars are hard and dense with low moisture permeability. These characteristics are not compatible with limestones, sandstones and brick which are usually soft and porous materials. In fact cement based mortars can damage such materials. It is now widely recognised that traditional buildings constructed of stone and brick benefit both physically and aesthetically from lime mortars, renders and plasters.
How should putty lime be stored?
Putty lime should be stored in airtight conditions. Traditionally it was stored in pits covered with a layer of water. Nowadays putty lime is usually stored in plastic tubs or polythene sacks.
How should hydraulic lime be stored?
Hydraulic lime powder should be stored in sealed bags in dry, well ventilated conditions and used within 6 months of date of manufacture.
Which sands and aggregates should I use in mortars, plaster and renders?
Clean well graded sands are essential for successful mortars, plasters and renders. Carefully graded crushed limestone and chalk can also be used in formulations for traditional and historic buildings. Study of historic mortars can be useful in determining the correct aggregate for a given situation.
How much water should I add to a pre-mixed putty lime mortar?
As a rule never add water to a pre-mixed putty lime mortar. Thorough mixing will impart a plasticity suitable for most applications. A small amount of water is sometimes added to plasters and renders but added water invariably means potential shrinkage problems.
What is the shelf life of putty lime hair plaster?
Haired lime plaster should not be stored but used as soon after the hair is added as possible. The caustic nature of putty lime will weaken the hair if left for a prolonged period of time in its wet state.
What type of surfaces can be limewashed?
Limewash is most successful when applied to porous, permeable surfaces like limestone and lime plaster. It does not take very well to cement or hard gypsum plasters but can be used on softer gypsum plasters. Limewash is suitable for both interior and exterior surfaces.