Cementation

## Cementation Cementation

**Cementation** is the operation of heating a metal with a powder or cement to cause surface transformation or to extract or add components. In alchemical and metallurgical practice, cementation was used to purify gold (removing base metals from gold alloys), to color metals (producing surface layers of different composition), to harden metals, and to attempt transmutation. The operation involved packing the metal (often in the form of thin plates or granules) in a crucible with layers of cementing powder, sealing the crucible, and heating it for extended periods. The cementing powder would react with the metal surface, causing transformation.

Cementation could be used for various purposes: purifying gold by cementing with a mixture containing salt and other materials, which would remove silver and base metals from the gold; coloring copper to resemble gold by cementing with materials that would produce a golden surface layer; or attempting to transmute base metals by cementing with materials believed to contain the tincture or virtue of gold. The operation required careful preparation of the cementing powder, proper packing of the metal and powder in layers, sealing of the crucible to prevent escape of vapors, and prolonged heating at high temperature. The cemented metal would then be removed, cleaned, and examined for the desired transformation.

In alchemical symbolism, cementation represented the transformation of surface into depth, the penetration of virtue from the cement into the metal, and the gradual perfection of matter through prolonged contact with perfecting agents. The operation was associated with the theme of gradual transformation, with the idea that perfection could be communicated from one substance to another through intimate contact and heat. Cementation represented the principle that transformation could occur through the action of one substance upon another, that the virtue of the perfect could penetrate and transform the imperfect. Cementation thus represents both the practical operation of surface transformation through heating with powders and the symbolic operation of gradual perfection through contact with perfecting agents.

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