Wednesday, 22 May 2019

History of Chiltern brick-making

History of Chiltern brick-making

Sir, — I was concerned after reading your report about the Emmer Green chalk mines (Standard, May 3) that all these scouts are going to take away the idea that bricks are made mostly of chalk with some clay.

The addition of chalk may have been the case for the yellow or white bricks when these became fashionable from the late 18th century but does not reflect the beautiful red/orange/pink tones of the typical Chiltern bricks.

We have one very good example of such pale, fashionable brickwork in Henley, at Longlands in Hart Street, just opposite the west front of St Mary’s Church. With the building being so close to the river, the bricks could have been brought up from London, where the fashion for pale bricks was widespread in the later Georgian and Victorian periods.

Please allow me the following clarifications about Chiltern brick-making:

1. Local bricks were made of clay with some coarse inclusions, such as small flints and pebbles to help an even firing process.

2. The clay earth gives bricks the lovely red/orange colouring we see all over the Chilterns. Over-fired bricks turn blue and we can see them, used as blue headers, creating patterns.

3. Clay overlies the much earlier chalk formations and there are many hollows, ponds and ditches in the Chilterns, still evidence of where the clay earth, sand and pebbles were dug up.

4. Nevertheless, chalk has a most important role to play regarding the use of bricks for building. This is lime mortar.

5. The mined chalk was burned in lime kilns, locally if there was plenty of timber to do so. The burning of the chalk produced quick lime, which was turned into lime mortar.

6. Without lime mortar, no building, whether stone, flint or brick, could have been constructed before the invention of cement mortar.

7. Sand also plays a vital part in brick-making as the wooden moulds, in which each individual brick was formed, had to be sanded to make sure the sticky clay brick came away clean, ready for the drying shed before being stacked in the kiln or clamp for firing. The clamp was a temporary means for firing bricks, which was much used but, unlike the kiln, left no long-term evidence of its existence. — Yours faithfully,

Ruth Gibson

Henley Archaeological &
Historical Group

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