Class C limes are natural hydraulic limes prepared from limestones or chalks with clayey impurities. Artificial hydraulic limes are manufactured by mixing pozzolan with calcium hydroxide which enable the limes to harden even in damp conditions. Hydraulic limes were originally used in areas subject to frequent saturation or continuously damp conditions, and for hydraulic engineering works such as harbours and bridge piers.

Unlike normal dry putty, hydraulic lime does not need dry, airy conditions to set properly. It's made of a special type of limestone that contains natural impurities which allow the lime to set quickly and in wet conditions.

binder for plaster and mortar.