Mortar grade non-hydraulic lime putty slaked from Singleton Birch Lincolnshire chalk ‘burnt’ at c.1000°C. The cream coloured putty is matured for a minimum of 6 months, and contains a small proportion of <3mm flint and un-burnt chalk particles. Superfine grade lime putty is also available (RJ1.01).
Tradesmen familiar with the use of lime putty, and with experience of its successful use should be employed. Accurate volumetric site mixing is essential. Lime putty mortars do not perform as gypsum, cement, or hydraulic lime. Non-hydraulic lime sets only by reaction with atmospheric carbon dioxide in the presence of moisture.
This ‘carbonation’ is a slow process and control of the drying and curing process by ‘tending’ and protecting is crucial to success and long term performance. Do not use in temperatures below 5°C or above 25°C. Protect from frost.