Hi All,
thanks again for this forum and to everyone who contributes . I have read Hokes books , and have been buying scrap karat gold jewellery for past 6 months and thought I was getting good at this , but yesterday bought a piece of gold that confuses me . Its a heavy mens 9k bracelet and is fully hallmarked . I recently bought a plated item in error and it took the application of acid direct to item to show a fizzing green reaction, and then the plate had worn off revealing a white base metal.
When buying the item I used the touchstone and the item passed no problem. Worried that the item may be heavy plated I repeated the touchstone test on the same link again scraping heavily , and made three lines from the gold. All passed the 9k acid test. Also looking at where i had scraped the item , the item seems gold beneath the outside ie, solid gold metal and no sign of white or copper base. Happy enough with results I bought it.
Then I placed a drop of acid onto the item itself. This leaves a darkend area on the gold (reddish /brown ), and the acid that wiped off has a green colour . Worried I got some other items to test in same manner . A known 9k item, and a known plated item . On the touchstone the plated item disappears and the two 9 k items pass . i also tested the lines by adding silver test solution to them ( nitric / potassium ) the two 9 k don't fade.
When acid is directly put on the plated item if fizzes green , and the plating is removed. When applied to the known 9k item there is no reaction except the gold slightly darkens . Added to my new bracelet , the gold darkens but left for a while appears blueish green , but with no major fizzing like the plated item does.
So i specific gravity tested the item . Its 61.6 g and i got displacement of 5.6g which would give density of 11, which I think is ok for 9k gold .
From what I read any green reaction to the acid means it's plated but is this true ? With the specific gravity test and passing the touchstone test passing can I presume from those tests that its just the copper in the 9k reacting and causing this ?
Thanks for your help !
K
thanks again for this forum and to everyone who contributes . I have read Hokes books , and have been buying scrap karat gold jewellery for past 6 months and thought I was getting good at this , but yesterday bought a piece of gold that confuses me . Its a heavy mens 9k bracelet and is fully hallmarked . I recently bought a plated item in error and it took the application of acid direct to item to show a fizzing green reaction, and then the plate had worn off revealing a white base metal.
When buying the item I used the touchstone and the item passed no problem. Worried that the item may be heavy plated I repeated the touchstone test on the same link again scraping heavily , and made three lines from the gold. All passed the 9k acid test. Also looking at where i had scraped the item , the item seems gold beneath the outside ie, solid gold metal and no sign of white or copper base. Happy enough with results I bought it.
Then I placed a drop of acid onto the item itself. This leaves a darkend area on the gold (reddish /brown ), and the acid that wiped off has a green colour . Worried I got some other items to test in same manner . A known 9k item, and a known plated item . On the touchstone the plated item disappears and the two 9 k items pass . i also tested the lines by adding silver test solution to them ( nitric / potassium ) the two 9 k don't fade.
When acid is directly put on the plated item if fizzes green , and the plating is removed. When applied to the known 9k item there is no reaction except the gold slightly darkens . Added to my new bracelet , the gold darkens but left for a while appears blueish green , but with no major fizzing like the plated item does.
So i specific gravity tested the item . Its 61.6 g and i got displacement of 5.6g which would give density of 11, which I think is ok for 9k gold .
From what I read any green reaction to the acid means it's plated but is this true ? With the specific gravity test and passing the touchstone test passing can I presume from those tests that its just the copper in the 9k reacting and causing this ?
Thanks for your help !
K