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 Post subject: Identifying gold plate/rolled gold using acid testing
PostPosted: Wed Jan 09, 2019 8:06 pm 
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Hi,

I need some help in identifying gold plated items. I have an acid test kit - would a gold plated (gilt, rolled gold, vermeil, etc.) test as carat gold using the metal strike on stone method?

How do I determine a gold plated item versus solid gold without damaging it (i.e. I want to avoid scratching through the gold layer or applying acid directly to the piece)?

Thanks,

Shelley


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Sun Jan 13, 2019 12:08 pm 
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Short answer, you can't. There is an instrument that can test the whole item electronically, but at something like £10,000 each, unless you are testing non stop, all day and every day, hardly worth while. The approved method is to file a nick into the surface and apply the acid to that, if you just rub the surface on the stone and put the acid on the streak there is a danger that the surface gold will give an erroneous high reading. You could always pick an inconspicuous spot to file or I am sure I have seen advertised a solution that will "flash" a coating of gold on an item and cover up any file marks. Alternatively, tool shops, at least in the UK, sell "Pen platers" where the item is made the cathode and the pen, which contains the plating solution, fed out through a felt "nib", is made the anode. By wiping the pen across the file marks, the affected area can be replated quickly and effectively. The amount of work you are doing will determine whether such an investment will be worthwhile, although they are not very expensive.


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Sun Jan 13, 2019 6:14 pm 
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Thanks Alan, this is very helpful and answers almost all of the things I was unclear about. I will look into the flash coating and pen plating products you mention.

I asked this question because I had a couple of watch keys that I presumed were gilt that tested negative for gold using a scratch test. Is a negative test always conclusive, or are there provisos around this as well?

Another item ‘fizzed’ when it came in contact with the acid - I’ve been told this is indicative of gold plating.

Cheers,
Shelley


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Sun Jan 13, 2019 11:10 pm 
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Sometimes a strong magnet is useful.
If something is attracted to the magnet, it is not gold.


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Mon Jan 14, 2019 6:49 am 
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Good tip, Barbra. Thanks!


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Mon Jan 14, 2019 11:21 am 
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A negative test is as conclusive as the care taken in applying it. If something fizzes in contact with the acid it is because the acid is touching base metal, so the gold plate must be very thin, worn or nonexistent. When dealing with antique items there are two factors to consider, first, the gold plate is likely to have been put on thicker, fire gilding and rolled gold thickest of all, but at the same time there has been much longer for the gold to wear off. I would recommend getting hold of some scrap or broken items and play with them, applying the acid to the surface and filed areas to get a feel for how metals react under various circumstances.


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Mon Jan 14, 2019 1:28 pm 
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What I normally do when testing older pieces is
1. Look for any assay stamps, hallmarks or maker's marks.
General information for those unfamiliar:
GP=gold plated
GEP=gold electroplated”
RGP=rolled gold plate
HGE or HGP=heavy gold electroplate
https://bellatory.com/ wrote:
Assay" means “a test." A gold assay test shows the percentage of gold in relation to other metals in an item. It is a test of value rather than of quality. Expensive materials can be poorly manufactured and, similarly, cheaper metals may have been worked with exquisite craftsmanship. An assay or hallmark is an objective chemical test. Deciding the quality of an object is subjective.

Hallmarks show that an assay test has been carried out on the gold object to confirm its karat rating. The reliability of the hallmark depends upon the country of origin. State-controlled assay offices imprint a mark onto the gold showing the year and place of assay together with the percentage of gold found, or the karat rating. The hallmark is very small so you may need a magnifying glass or jeweler's loupe to see it clearly.

If the hallmark is clear and easily readable, this is the quickest way to check the gold content of an item. However, over time some of these marks can become worn, and some may have been deliberately tampered with.


2. Gold does not oxidize (i.e. rust) like many other metals. Therefore, diligently check the piece with magnification at all points of possible wear. Do you notice discoloration or areas where a base metal seems to be peaking through?
Sometime solder can oxidize and try to fool you. Rub the area with a polishing cloth and check again.

The most important thing an appraiser has to know is when an object is clearly out of their area of expertise.
Admit it and turn the assignment down. :D


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Mon Jan 14, 2019 7:10 pm 
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Thank you both, this is incredibly useful! I'll go back now and re-test a few of the pieces that were in contention with these tips in mind.


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Tue Jan 15, 2019 6:23 pm 
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That is why I like to see a (UK) Hallmark, it gives a definite and incontestable date within 1 year for the mark, therefore very close to this for the making.


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Wed Jan 16, 2019 6:41 pm 
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Just as an interesting side:
Our forefathers, here in the US, made the decision that hallmarks would not be used in America because it impeded commerce. They felt that the public would weed out the nogoodniks without government involvement.

Wise decision?
Absolutely not.


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Thu Jan 17, 2019 9:56 am 
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Barbra Voltaire wrote:
Just as an interesting side:
Our forefathers, here in the US, made the decision that hallmarks would not be used in America because it impeded commerce. They felt that the public would weed out the nogoodniks without government involvement.

Wise decision?
Absolutely not.


King Edward I of England enacted a statute requiring that all silver articles must meet the sterling silver standard (92.5% pure silver) and must be assayed in this regard by 'guardians of the craft' who would then mark the item with a leopard's head. In 1327 King Edward III of England granted a charter to the Worshipful Company of Goldsmiths (more commonly known as the Goldsmiths' Company), marking the beginning of the Company's formal existence.
that granting of permission was what the early americans rebelled against ...thank god...and I agree.
Im not a jewelry professional but i am a construction professional that had to leave the kingly state of california because after 25 years of being in construction and then allowing my "permission to do business"(contractors license) to lapse because i was busy doing construction for someone that had one i was no longer eligible to do the same business i was in for most of my life because i didn't have 4 straight years of being under someone elses supervision ...regardless of having a spotless record for the 15 years i did have a license.
It is that kind or "consumer protection the early americans rebelled against and we need to go back to the day of a man being able to do business with out the governments permission.$5 years of living in a state with nothing more then a traffic violation and i cant write contracts for my life long trade!!!
rant over...45 ye


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Thu Jan 17, 2019 6:33 pm 
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That's a tough break. :(


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Thu Jan 17, 2019 6:34 pm 
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Fair enough.....but MY job would be a lot easier if everything had a hallmark, year stamp, maker's mark and assay office stamp.
You Stairman, of course, would be exempt. :wink:


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Thu Jan 17, 2019 8:09 pm 
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I think Stairman has the wrong end of the stick. Even in the UK with pretty strict Hallmarking laws, you don't need permission to make things of gold and silver, you just need to prove that they are of the standard you claim for them before sale. In a sense though, the Founding Fathers had a point, in that I have a delay of a week or ten days in manufacturing whilst items are hallmarked. Given that it is moderately expensive to have single items marked, there can be a greater delay while I build up enough items to get the bulk rate.


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 Post subject: Re: Identifying gold plate/rolled gold using acid testing
PostPosted: Thu Jan 17, 2019 9:38 pm 
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I think it is the ultimate safeguard for public safety.
Certainly, all costs are recouped upon final sale.

Russia (also with impressive hallmarking and assay provisions) also insists all gems in rings have been identified by a gemological lab.

I believe countries which do not have hallmarking standards are in the minimum, both in Europe and Asia:

More Information:
https://theassayoffice.com/internationa ... tion-marks


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