DIFFERENT TYPES OF LIME?
There are different types of lime, in different forms for different uses, and all are now supplied as convenient, ready-to-use materials. While the basic principles of their production and use are common to all of them, they each have their particular properties.
The most commonly encountered are:
'Lime Putty is produced as described in the Lime Cycle. The consistency of soft butter, it should be at least 3 months old before it is used - it continues to improve the older it becomes, hence it is often described as "matured" lime putty. It cures simply by exposure to air, combining with carbon dioxide - which is why it is also known as "air lime". This process of combining with carbon dioxide is known as carbonation.
'More information regarding our Lime Putty can be found on our products page.
Natural Hydraulic Lime
Certain types of limestone contain inclusions of silica. When such limestone is burnt, these naturally occurring "impurities" convert to compounds that cause the lime to set when added to water. Such lime cannot therefore be slaked to produce a lime putty, as it would simply solidify.
It is therefore slaked by spraying with a precisely metered quantity of boiling water, just sufficient to change it from quicklime (calcium oxide) to calcium hydroxide. The heat produced by the exothermic reaction that this causes is sufficient to leave the resultant lime as a dry powder, known as natural hydraulic lime. Natural hydraulic lime, mixed with sand and water to make a mortar, sets initially by reacting with the water (the hydraulic set) and then goes on to carbonate (combine with carbon dioxide) in the same way as a mortar made from lime putty.
'More information regarding our Natural Hydraulic Lime can be found on our products page.