Joseph Gwinn wrote:



Before the advent of electroplating, precious metal smiths used the
extremely poisonous technique of "fire gilding" to gold plate silver
objects. This was done with gold amalgams.

I had not heard of this technique.

http://en.wikipedia.org/wiki/Gilding#Fire-gilding


"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."
http://www.medterms.com/script/main/...ticlekey=39600


"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."
http://www.metmuseum.org/toah/hd/fire/hd_fire.htm

If it was before electroplating, it
was back when an old man was 45, so they probably didn't manage to die
of the mercury fumes.

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."
http://www.worldwidewords.org/qa/qa-mad2.htm


I recall reading that the ancients knew how to electroplate, although
they didn't understand how or why it worked.


"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."
http://electrochem.cwru.edu/ed/encyc...lectroplat.htm


"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."
http://en.wikipedia.org/wiki/Electroplating#History

--
Abrasha
http://www.abrasha.com