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Wax seals
Wax seals
In the West the use of wax or metal seals spread as from the Middle Ages, while sealing wax and paper were used to seal documents only as of the sixteenth century.
These materials were seldom used alone but were generally mixed with other substances. Wax seals were based on beeswax mixed with other ingredients to obtain a more suitable substance for the impression. In fact, pure beeswax was very soft and not very durable so resinous substances, such as pitch or rosin, were added to make it more resistant, and turpentine or linseed oil were added to enhance its pliability. Other fillers were then added, including earth, chalk, ash or organic matter.
No colouring agents were added to the wax compound until the eleventh century and prior to this period seals were yellowish brown in colour. Subsequently, it became standard practice to add various mineral pigments to the amalgam to colour the impressions. Red wax was created by adding lead oxide (minium) or mercury sulfide (cinnabar), while copper carbonate or acetate or chromium oxides were added to make green wax. Black wax was obtained by adding carbon from charred wood to the paste.
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