Keys to the Past

Glossary

Alum

Chemicals used to 'fix' coloured dyes from plants and animals to a piece of cloth - so it will not wash out or fade over time. This has been found in large amounts on the North Yorkshire coast in the shale type rocks. There are similar chemical compounds based on the substitution of Potassium (K) by Sodium (Na) and Ammonium (NH4).

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