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Showing the grain structure in gold


#1

Hi everyone, I’m new to the forum, & this is my 1st post, so I hope
I’m using the right e-mail (?)

Does anyone know anything about showing the grain structure in gold?
Apparently you heat it to a specific temp, hold it(?) then acid
etch. That’s all I know. I need to know what type of gold, temp, hold
times, & recommended etchant. Any leads would be great, you can do
the same with silver from what I understand…

TIA for any help!!

Sincerely,
John Lewis Jensen


#2

Here is a web source of some procedures for metallographic etching.
Includes silver and other precious metals but not gold.

http://www.kaker.com/etch/java/data/data_electro.html

You might check :

G. Petzow, Metallographic Etching, ASM (American Society for
Metals), 1978. I don’t have a copy. For other than pure gold you
can etch out the alloy metal and expose the gold grains, but I
don’t have a cookbook procedure.

Jesse


#3

a procedure for metallographic etching of gold can be found in the
ASM metals handbook volume 8 8th edition “Metallography, Structures
and Phase diagrams”. It uses a cyanide containing alkaline
electrolyte:

80 grams potassium cyanide
40 grams potassium carbonate
50 grams  gold chloride
water to make 1000 ml

cell voltage is 7.5 for 2 - 4 minutes

Jesse


#4

Better use a very good fume cabinet. Cyanide ain’t no joke! Also
rubber apron, gloves, face shield and keep any and all acids away
from this solution!