This article examines the career of Erasmus Purling, an English engineer who wrote a short alchemical treatise in 1657. After serving the Royalist cause in the late 1640s, he joined the Commonwealth forces in the early 1650s. He then attempted to manufacture and market a tin alloy supposedly resembling silver, first in England, where he was opposed by the London pewterers and imprisoned. In 1657, he was granted a monopoly privilege from the French Crown for his invention, which he promoted in his alchemical pamphlet. This publication, as well the other works he used to promote his discoveries, attracted the hostility of Parisian pewterers. They attempted to bring his enterprise, and transmutational alchemy in general, into disrepute. Despite this, Purling's pewter sold well, attracted influential investors, and was even protected by a second privilege obtained in 1659. At the Restoration, Purling returned to England, where he tried to implement similar projects, probably without success. Nevertheless, his troubled and little-known career illustrates several facets of alchemical entrepreneurship in the seventeenth century, including conflicting relationships within the world of crafts and trades and ambiguous relationships with state administrations on the eve of the reign of Louis XIV.