How-to · conservation
Cleaning an ancient coin without destroying it
Distilled water and patience first; disclose everything done; never strip a silver coin's toning or a bronze's stable patina.
1. Decide not to. The value sits in the surfaces: a stable green or brown patina on bronze and cabinet toning on silver are part of the object, and a coin stripped to bright metal has lost a century of history and most of its price.
2. Start with distilled water and a soft brush, then, for bronze, days of soaking with occasional brushing. For silver the most that should be tried at home is a short lemon-juice or sodium-bicarbonate bath.
3. Treat bronze disease and nothing else. Powdery, pale green, spreading spots are active chloride corrosion: remove them mechanically, soak in sodium sesquicarbonate over weeks, dry thoroughly and seal with wax.
4. Never use electrolysis, acid or an ultrasonic bath. They strip everything and shatter fragile flans; tooling (re-engraving worn detail) and smoothing are alterations the trade treats as damage.
5. Record the method under Preparation (cleaning method), note bronze-disease treatment as a condition risk, and let the disclosure line print it. A coin sold as "uncleaned" that has been cleaned is a misrepresentation on every platform's rules.
Sources
Cite this article
Stratum Study. "Cleaning an ancient coin without destroying it" (How-to). Stratum Study pack 2026.09, as of 2026-09-20. https://stratum.black/study/how-to/how-to-clean-a-coin. Accessed 2026-09-21.
@misc{stratum-how-to-clean-a-coin,
title = {Cleaning an ancient coin without destroying it},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/how-to/how-to-clean-a-coin}},
year = {2026},
note = {How-to article, Stratum Study pack 2026.09, as of 2026-09-20; sources: stratum. Accessed 2026-09-21.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.