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Re: Wollaston wire (was light bulbs)




Many thanks for that information, Chuck. I never did find out
from Mickey Walsh how it was done. New question: How is Wollaston
wire made? It is Tungsten wire (I think) with a .0001" platinum
core. After fabrication the tungsten is dissolved away with acid
leaving the very thin platinum wire behind.

Leigh

Wollaston wire is made of platinum, as small as 0.5 micron. According
to "Procedures in Experimental Physics" by John Strong (Prentice-Hall,
1944), it was used for string electrometers and sometimes for delicate
fuses.

The manufacturing procedure is clever. A much larger platinum wire is
electroplated with silver. The combination is then drawn down until
the platinum core is the desired diameter. After thorough cleaning the
silver is etched off with chemically pure nitric acid at a specific
concentration to minimize bubble formation and insure uniform etching.
The wire is then ready for annealing and mounting - carefully!