Quicklime

Quicklime is limestone (a rock rich in calcium carbonate) that has undergone a chemical change in a kiln, liberating it of all the carbon and water it holds, creating a very unstable material (calcium oxide) which needs to hydrate. Quicklime will do so very energetically with any moisture it comes into contact with, resulting in a strong exothermic reaction and the production of lime. The addition of water, slaking, has the potential to produce temperatures exceeding 250C very quickly. However, when creating a mortar the quicklime can reach these high temperatures as hot spots only, and the overall temperature of the mortar should not exceed 100C – the temperature at which the water turns to steam.

Quicklime is available in two forms; ‘kibbled’ which is granular, containing particles from 5-15mm, and finely powdered. Both of these are chemically identical, but kibbled is more dense than an equal volume of powder, and as mortars are usually mixed by volume not weight, mix proportions should be varied accordingly. (Kibbled expands to approximately 2.7 times its original volume, while powdered expands approximately 2.1 times.)

Quicklime can be used to make Lime Putty or a hot-mixed mortar. A hot-mixed mortar can make an excellent and very vapour permeable mortar, with a good ‘sticky’ consistency and high water retention. However the mixing process can take more time than alternatives and due to the heat given off the process can be quite dangerous if the correct precautions are not taken.

Quicklime (Calcium Oxide) is a highly reactive and quite dangerous material, please make sure you understand the risks and have taken suitable safety precautions before ordering. This material must be stored in a cool dry environment away from direct sunlight.

Note: Our powdered  Quicklime comes in a 25kg bag.