dental gold?

"Fire gilding: A perilous process for gold-plating in which an amalgam of mercury and gold is applied to an object and then exposed to heat to vaporize the mercury and leave the gold behind in a thin layer. Fire gilding also is applicable to plating silver, copper, and copper alloys. The process of fie gilding is still used when antique work is to be repaired or an exact replica made. Fire gilding is hazardous because mercury vapors are emitted even at room temperature, presenting an appreciable risk of mercury poisoning. Fire gilding is also called mercury gilding."

"The practice of amalgam gilding goes back many centuries. It was used by the Romans to apply gold onto silver, known as silver-gilt (Maryon

1971, p. 262), and in his twelfth-century book, On Divers Arts, Theophilus describes in detail how to gild a surface using an amalgam. An amalgam is any alloy of mercury with another metal, in this case gold."

They did in fact die of the cumulative effects of serious Mercury poisoning. BTW, the expression "Mad as a hatter" comes from the use of Mercury in the making of felt for the hat industry.

"Few people who use the phrase today realise that there?s a story of human suffering behind it; the term derives from an early industrial occupational disease. Felt hats were once very popular in North America and Europe; an example is the top hat. The best sorts were made from beaver fur, but cheaper ones used furs such as rabbit instead.

A complicated set of processes was needed to turn the fur into a finished hat. With the cheaper sorts of fur, an early step was to brush a solution of a mercury compound ? usually mercurous nitrate ? on to the fur to roughen the fibres and make them mat more easily, a process called carroting because it made the fur turn orange. Beaver fur had natural serrated edges that made this unnecessary, one reason why it was preferred, but the cost and scarcity of beaver meant that other furs had to be used.

Whatever the source of the fur, the fibres were then shaved off the skin and turned into felt; this was later immersed in a boiling acid solution to thicken and harden it. Finishing processes included steaming the hat to shape and ironing it. In all these steps, hatters working in poorly ventilated workshops would breathe in the mercury compounds and accumulate the metal in their bodies.

We now know that mercury is a cumulative poison that causes kidney and brain damage."

"The early history of electroplating may be traced back to around 1800. A university professor, or in modern terms: a chemist, Luigi Brugnatelli is considered as the first person to apply electrodeposition process to electroplate gold. Brugnatelli was a friend of Allisandro Volta (after whom the electric unit "volt" has been named) who had just a short time before discovered the chemical principles that would make possible the development of "voltaic" electrical cells. Volta's first actual demonstration of that was called "Voltaic Pile". As a consequence of this development, Brugnatelli's early work using voltaic electricity enabled him to experiment with various plating solutions. By 1805 he had refined his process enough to plate a fine layer of gold over large silver metal objects."

"Modern electrochemistry was invented by Italian chemist Luigi V. Brugnatelli in 1805. Brugnatelli used his colleague Alessandro Volta's invention of five years earlier, the voltaic pile, to facilitate the first electrodeposition. Brugnatelli's inventions were repressed by the French Academy of Sciences and did not become used in general industry for the following thirty years."

[snip]

Good lord. That would be able to kill them way before the diseases usual in the day.

[snip]

The articles I read many years ago were talking about ancient Egypt or China, at least 1000 years before the 1800s, well before the invention of the battery by Volta in Italy. What was described was a battery and plating cell all in one. It might have been for copper plating. It was clear that ancients did not understand why the thing worked, only how to replicate it.

Joe Gwinn

Your probably thinking of the Baghdad batteries.

These were ancient ceramic jars with a tar seal and a sheet of copper and an iron rod inside.

Speculation in some circles goes something like this:

"What the hell are these things?" "Could be a battery." "What the hell did they need a battery for, they didn't have any transistor radios?" "They must have invented electroplating!"

Anyone who has made a battery for a science fair project knows that iron and copper have only about 3/8 v potential between them and make a pretty crappy battery.

If you wanted to do any plating, you would need at least a dozen of them in series. If the ancient Mesopotamians knew the difference between series and parallel.

Paul K. Dickman

Apparently they did know the difference:

"In 1936, at Khujut Rabu'a near Baghdad, was found a small pottery jar, about

5-1/2 inches high and 31 inches in diameter. Inside was a cylinder of thin copper, closed by an asphalt plug. Inside the cylinder was a rusted iron rod. Similar jars, without the metal cylinders and rods, had been found at the ruins of Seleucia-on-the- Tigris, twenty-four miles below Baghdad. Three larger jars containing respectively ten copper cylinders, ten iron rods, and ten asphalt plugs, not yet assembled as in the Khujut Rabu'a jar, turned up at Ctesiphon, across the Tigris from Seleucia. All these objects date approximately from Roman Imperial times. The only use that anybody has been able to conceive for them is as battery cells for electroplating small metal objects with gold. It has also transpired that the silversmiths of Baghdad, within the present century, used a similar apparatus for gold-plating their works. Those who knew about this method long assumed that the silversmiths had learned their electroplating from western sources. Although ar­cheologists are not yet agreed about the mysterious jars, we must at least consider the strange possibility that electroplating was discovered in Iraq in ancient times; that, despite the ravages of the Mongols in + XIII, this technique survived down to the present century; and that, nevertheless, it failed to spread to other lands, presumably because the metal workers kept it secret."

"The Ancient Engineers", L Sprague Le Camp, 1960

Tom

Bingo! This is exactly what I was remembering.

Joe Gwinn

Ifeel that I have to set the record straight:

Current practice in dentistry is to remove decay and old fillings before preparing a tooth for a crown. The next step typically is to rebuild the tooth. This can be done with composite materials or silver-mercury amalgam. The tooth is then shaped for the crown and an impression is taken. The result can be a crown over an existing mercury filling. This is accepted practice in the USA. In the past gold crowns have been done over existing old mercury fillings for many different reasons. When you heat the gold crown on a tooth you have no idea if there is mercury present underneath. The heat required to melt the gold will either volatilize the mercury or create a gold amalgam. Neither is good for you: the mercury vapor is toxic and the amalgam will release the mercury when it is heated the next time for casting.

In the US I am not aware of the teaching of gold amalgam in dentistry in the last 50 years.

There is no way to economically cash in a gold crown. Your best choice is to play with it and make something. The Karat content of the gold varies all over the place. I suppose the standard gold tests would let you know what it is.

Charles Friedman DDS Ventura by the Sea where we extract black gold from the ground