"Toning" is a nice, polite word for "mild corrosion".
Most toning is natural, because Earth is a rather nasty planet, if you're a piece of shiny metal. The air, the water, the soil, and even the hands and fingers of the planet's inhabitants, are all conspiring to turn pieces of shiny metal back into the ores from whence they came.
All sorts of things can cause corrosion, and so toning can take many different appearances. A nice even toning is usually caused by atmospheric conditions; blotchy toning may be caused by something solid or liquid coming into contact with the coin. Brightly coloured toning is usually the result of "thin film optics", the same laws of physics that cause colours to appear on oil slicks and soap bubbles. In the case of a coin, the "thin film" is a layer of oxidation and corrosion by-products. Red colour is caused by the thinnest films, as the film gets thicker it progresses through the rainbow (orange, yellow, green and blue). The colour after blue is black, because the "thin film" then becomes too thick to allow light to pass through it.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
Posted 01/10/2023 7:43 pm
