Lime putty suitable for building can only be made by slaking which must start by reacting soft-burnt high calcium quicklime (not hydrated lime) with an excess amount of water. Our lime putty is slaked from fresh soft-burnt high calcium quicklime, screened and then aged for a minimum of three months. This produces a product that is suitable for brick and stone mortar as well as fine plaster work. Three years of slaked lime putty aging takes place to produce finer lime putty with better coverage and performance for our Old World European Limewash. Slaked Lime Putty for Frescoes is aged for ten years. The aging process ensures that the lime particles are extremely fine, making this product the ideal choice for conservation work on frescoes. Made from non-hydraulic high calcium limestone with a 98% purity rating. Our slaked lime putty products meet and/or exceed ASTM C1489 – Standard Specification for Lime Putty for Structural Purposes. Heritage Pure Lime Putty ingredients also meet or exceed ASTM C5 – Standard Specification for Quicklime for Structural Purposes. Weight: 36 lbs Beware of “lime putty” products that do not meet ASTM C5 as they are most likely made from dry hydrated lime meaning they can be soaked but cannot be slaked. Dry hydrated lime is a plasticizer not a binder. No length of time soaking dry hydrated lime in water will ever produce an appropriate binder.