The Pawnbrokers Guide to Testing Metals

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Your welcome qst42know.

I've been using these same methods for 25 years.

A couple of other tips.....

A nice smooth dark river rock makes a great touchstone. Or any dark slab of microcrystaline quartz cut from a geode etc..

I keep a tupperware tub with a soultion of water and baking soda that I drop all the tested articles in to neutralize the acid then rinse in clean water.

Considering the onset of HIV, ADS Hepatititus etc... I also have a small tub with 50/50 water and bleach. All the earrings studs etc get a soak in that for a bit before I start really testing them. Play it safe.


PB
 
Very smart about the disinfection procedures Bob. You continually impress me with your thoughtfulness.
 
Excellent article, Bob. Probably the most complete writing that I've seen on the subject.

The "red acid", for testing silver, that he speaks of, is a combination of nitric acid and potassium dichromate.

He says that there can be cadmium and/or cyanide on silver contact points and that these make it very hazardous to melt. Most do contain cadmium. None, however, contain cyanide, unless the seller was trying to refine them himself, which is unlikely. In any case, don't melt silver contact points.

His discussion of silver flake, plated out of photo fixer, is very poor and incomplete.

Concerning gold plate. There is a thin layer of nickel plate underneath most all gold plate. The gold is so thin that it only takes a few strokes with a pencil eraser to rub a spot of it off. This exposes the white nickel below, which is easily seen in contrast to the yellow gold around it. I have used this test 1000s of times. I got so good at it that I could get a pretty good estimate of the thickness of the gold plating. Of course, this won't work for gold filled.

I remember an excellent article in the "Gold Bulletin", many years ago, that used a white touchstone. I think that it got heavily into PGMs also. I've tried to locate it, but have had no success.
 
Does anyone know the ratios of acid in the test solutions? Instead of paying 29.00 on ebay I would like to make my own? I imagine its just different formulations of nitric and Hcl?

mlgdave
 
mlgdave said:
Does anyone know the ratios of acid in the test solutions? Instead of paying 29.00 on ebay I would like to make my own? I imagine its just different formulations of nitric and Hcl?

mlgdave

I can't find the post, it's by Harold or GSP (sorry can't remember who)

so I'll just write the ratios:
10K - 22.2ml nitric to 7.4ml distilled water
14K - 23.7ml nitric to 5.9ml distilled water to 10 drops of HCL
18K - 5.9ml nitric to 5.9ml distilled water to 22.2ml HCL

for 22K i just used 1 part nitric to 4 parts HCL

That is working great for me.
 
jimdoc said:
Thanks for bumping this thread, The Pawnbrokers Guide to Testing Metals needs to be seen by all newbies.

No thanks on your spam.

Jim

Who? What? Why? and When?
 
samuel-a said:
jimdoc said:
Thanks for bumping this thread, The Pawnbrokers Guide to Testing Metals needs to be seen by all newbies.

No thanks on your spam.

Jim

Who? What? Why? and When?


They seem to have been booted for the spam.
Spam usually disappears faster here than in Rosie O'Donnel's refrigerator, and that is a good thing because spam sucks.

Jim
 
samuel-a said:
mlgdave said:
Does anyone know the ratios of acid in the test solutions? Instead of paying 29.00 on ebay I would like to make my own? I imagine its just different formulations of nitric and Hcl?

mlgdave

I can't find the post, it's by Harold or GSP (sorry can't remember who)

so I'll just write the ratios:
10K - 22.2ml nitric to 7.4ml distilled water
14K - 23.7ml nitric to 5.9ml distilled water to 10 drops of HCL
18K - 5.9ml nitric to 5.9ml distilled water to 22.2ml HCL

for 22K i just used 1 part nitric to 4 parts HCL

That is working great for me.


I'm new here, so lots of basic questions still.

What are the conce trations of the nitric and HCl initial solutions? Or, does anyone know of a resource here with the info?

Thanks!
 
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