In my ongoing series of questions dealing with things I never needed
to know before my current job…
We do a lot of sizings, repairs, and alterations on jewelry we
didn’t make, like most retail jewelers-- but I never worked in one
before.
We have acids to test various karats of gold. But what if a piece is
not marked, resists the 18k acid, and is white. It could be 18k
white-- or palladium or platinum. Mostly, it is easy to tell from the
color and weight, but not always.
Is there a definitive test?
There is a slip of paper posted at work that describes the three
metals’ reactions to iodine. Sounds great, but yesterday, I did a
side by side test on known samples, and the iodine did absolutely
nothing on any of them. Is something wrong with the test, or my
iodine?
Are you saying that when you put iodine (which is orange-brown) on
platinum, it should lose its color? And change color decisively on
the other metals? Are we talking about putting the iodine directly
on the sample, as opposed to rubbing a streak on the testing stone?
How about 18k gold-- the same as 14?
Are you saying that when you put iodine (which is orange-brown) on
platinum, it should lose its color? And change color decisively on
the other metals? Are we talking about putting the iodine directly
on the sample, as opposed to rubbing a streak on the testing
stone? How about 18k gold-- the same as 14?
Yes, paint it on and the solution will change color…
Thank you, Andy. I tried the test again, using lightly sanded flat
sizing wire of pt, pd, 18kw and 14kw. Just when I was ready to give
up on changes, the iodine did, indeed turn clear on the pt. It just
took several minutes.
The pd stained black and reddish. Both golds reacted the same-- they
turned what I would call yellow-gray, and dull (the others stayed
shiny).
Just then, our senior goldsmith came by and looked at my efforts. He
fetched the 18K testing acid and put a drop on each of the samples.
The pt did nothing (remained clear); the pd drop turned distinctly
yellow in a matter of 10 seconds or less; the golds stained
red-brown.
So now I feel equipped to distinguish decisively among the white
metals-- as long as they’re not some weird alloy.
I will add, for others new to all this, like me-- the red-brown
stain on the gold did not sand out nearly as easily as the other
marks, so I would avoid doing this. After all, you can ID the golds
using the acid and the rubbing stone.
Thank you, Andy. I tried the test again, using lightly sanded flat
sizing wire of pt, pd, 18kw and 14kw. Just when I was ready to give
up on changes, the iodine did, indeed turn clear on the pt. It just
took several minutes.
The pd stained black and reddish. Both golds reacted the same-- they
turned what I would call yellow-gray, and dull (the others stayed
shiny).
Just then, our senior goldsmith came by and looked at my efforts. He
fetched the 18K testing acid and put a drop on each of the samples.
The pt did nothing (remained clear); the pd drop turned distinctly
yellow in a matter of 10 seconds or less; the golds stained
red-brown.
So now I feel equipped to distinguish decisively among the white
metals-- as long as they’re not some weird alloy.
I will add, for others new to all this, like me-- the red-brown
stain on the gold did not sand out nearly as easily as the other
marks, so I would avoid doing this. After all, you can ID the golds
using the acid and the rubbing stone.
Hi Noel, You are absolutely right about iodine staining gold and it
being difficult to remove. I use it to age antique jewelry that I
have restored. Have fun. Tom Arnold