H I S T O R I C A L Q U I C K L I M E & E A R T H P L A S T E R / M O R T A R R E P R O D U C T I O N
It is now widely considered the core mortar used extensively for the majority of historic solid stone wall construction consisted of an earth or sand combined with a locally produced quick lime (hot lime). Generally the above mortar would be mixed ‘hot’ onsite and used as a stone bedding material and to construct the core of a solid masonry ‘mono’ wall. The outer pointing finished with a more expensive and durable sand and quick lime mortar.
The aim of the trial was to reproduce a historic usable mortar from locally sourced natural materials in this case from East Devon & West Dorset. The mortars would be authentically made based on traditional technics and methods. Small batches of chalk / lime were fired using a mixture of coal and seasoned hard wood to an unregulated temperature of approximately 900 C.
Following burning for 12 hours the chalk was removed and crushed to a powder manually. A variety of local earths and sand aggregates were selected, some with a high clay content some with out. The trials consisted of a reproduction historical plaster panel and various mortar samples. All of the local aggregates combined with the locally produced quick lime trialed work in both there workability and set following cure. The outcome is clearly positive with environmental advantages over industrially produced modern mortars. Natural mortars produced locally as per history suggests stand the test of time with substantial evidence from our historic build environment. They are ecological, sustainable, reabsorb carbon dioxide and will naturally decompose after use, making local historical quick lime and earth / sand mortars more relevant today than perhaps ever before.