Nearly finished repairing the folly, now for a little makeup on the new clunch stone. So what is clunch?
This little bit is from ‘Wiki’
“The stone is a chalk from the Lower Chalk of the Cretaceous age, the period of geological time approximately 145 – 66 million years ago. It is greyish-white to light beige in colour, often with a greenish tinge. The latter is due to the presence of glauconite, the potassium and iron aluminium silicate mineral that is also found in Kentish Ragstone. The stone has a gritty texture due to the frequent presence of shell fossils. This stone has been quarried at Totternhoe Quarry in Dunstable, Bedfordshire by H.G. Clarke & Son since 1920.
It is a particularly soft when quarried and subject to chemical and wind erosion as exposed material, i.e. when unrendered in paint, stucco or cement. It can be cut by a saw when in its softer state; when it has been quarried out of the ground it still contains a large amount of water. When the stone dries out it becomes harder, and is not as easy to cut.
Clunch is generically a soft limestone. It can be rich in iron-bearing clays or be very fine and white — in effect just chalk. It is used in various parts of East Anglia, where more durable stone is uncommon, and can be seen frequently in and around Thetford — mostly now for property boundary walls where not a long-lasting material, but it is also used for some building walls, especially in traditional agricultural buildings.
In Ely Cathedral it can be seen in some interior locations. The nearby village of Burwell has its civil parish magazine named after the building material. It is found in the village of Seale in Surrey and in Farnham.”
Originally the clunch used around the estate would have come from local clunch pits, nearly every village in SW Cambridgeshire has a clunch pit. The main one for Wimpole seems to be behind Cobbs wood farm in the woods but there is a bigger one in the local village called Orwell. Mostly the pits produced chalk and chalky marl mostly used for making floors and tracks although a type of cob brick was made with it too. The clunch (Burwell/Totternhoe stone) only appears in lens within the chalky strata so a pit only every produced a small amount of this stone.
Clunch weathers in many different ways however what we are seeing at the Folly is the semi hard face of the stone eroding in patches which leaves a soft fragile core face of stone exposed. These areas are more susceptible to weathering and the decay accelerates as the water gets into the stones and it crumbles fast. In addition once the outer face is lost it reveals the original light cream stone colour which looks blotchy when viewed against the rest of the surrounding stone, the original has built up a patina over the last 240 years. We had a building which looked like a Friesian Cow, patches everywhere.
The conservators have been using their artistic touch to colour these areas to match the surrounding weathered and aged stone – the appearance is to capture the years of lichen and algae growth.
View original post 218 more words