Plated juwelry

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Slochteren

Well-known member
Joined
Apr 3, 2015
Messages
156
Location
Netherlands
Hi,

I've got 1,5 kilo mixed gold plated juwelry, some say 10, 20 or 40 micron or walzgold. till what thickness will work in a sulphiric cell?

Thanks Paul
 
Paul from what I understand the cell will work on most thicknesses of plating, I think the trick is having very concentrated acid and not letting it get too hot or it attacks the base metals preferentially. Also you need to make sure all the surface plating is exposed, thicker plating will take longer so take your time or the acid will get too hot, keep the cell sealed after use,sulphuric will suck water from the atmosphere.
 
Theoretically different thicknesses will talk more of less time to de-plate. If you leave a thin plate in as long as it takes to de-plate a thick piece it may start to attack the base metals under the plating.

But since you are dealing with such thin plating anyway in practice it may make no difference. And when you recover the slimes to refine the gold you can get rid of the base metals then.
 
Slochteren said:
Hi,

I've got 1,5 kilo mixed gold plated juwelry, some say 10, 20 or 40 micron or walzgold. till what thickness will work in a sulphiric cell?

Thanks Paul
Any thickness will eventually strip. All you mentioned is thick gold plating and it will take awhile to strip. 40 microns would run about .08 grams per cm2. If the solution gets too hot, it will start eating the base metal and this will cause problems. By controlling the amperage, keep the solution temperature below 40C.
 
Hi,

thanks for the info, will run it thru a cell and keep the temperature below 40. Just wondering why isn't gold filled run thru a cell, or will the temperature get to high to fast?

Paul
 
Gold plating is a nearly pure coating of gold. Gold filled is an outer layer of alloyed gold. The alloy doesn't respond the same as nearly pure gold.

Dave
 
As Dave pointed out gold filled or rolled gold is base metal in a karat shell, the gold alloy can be 9-18k and can contain silver amongst other metals like zinc and copper. With plating although it's claimed to be 9-22 karat it's nearly pure gold with small additives to achieve the desired colour.
 
Hi,

i have sorted it a bit and there is 1 earring wich says 825 on the pin that goes thru the ear, does it mean only the pin is 825 gold or the total earring? I have no knowledge if jewelry. I got this 1,5 kilo for free.
There are also 4 older brooches, front looks like thin gold over kind of clay or other filling, and back side is silver. is that thin gold plated or "solid" gold?

Paul
 
Slochteren said:
Hi,

i have sorted it a bit and there is 1 earring wich says 825 on the pin that goes thru the ear, does it mean only the pin is 825 gold or the total earring? I have no knowledge if jewelry. I got this 1,5 kilo for free.
There are also 4 older brooches, front looks like thin gold over kind of clay or other filling, and back side is silver. is that thin gold plated or "solid" gold?

Paul

What I underlined above - are you sure it doesn't say 925 - I ask because 925 would indicate that earing is sterling silver that has been gold plated

the brooches - don't know (can't tell by your description) pics "might" help

Kurt
 
In my previous post, I assumed that the thicknesses were truly 10, 20, and 40 microns. mainly because of the mentioning of walzgold, which is often a true 20 microns and seems to mainly be used on watches. Do the markings actually say "Microns" or "Mikrons"? If not, it could mean microinches. There has always been a lot of confusion between the two. A microinch is only 1/40 the thickness of a micron.
 
About the 825 or 925 im not sure its very hard to see, will run it thru the cell and see what happens.
The thickness is written as Micron and Mikron on the different pieces, 80% of the pieces are watch cases and most are unmarked, must be relative thick plated because wenn i run a few thru the cell it puls 13 Amps at 10 volt. This will heat up a cell quick but i use 4 cells wen 1 gets to warm i use the next one.
I have added some pictures of the brooches.

front.jpg


detail.jpg


rear.jpg


Would warm dilute HCL seperate the front from the silver rear?

Paul
 
Assuming it is silver I would go with dilute nitric, even if it's not most metals will dissolve in nitric and hopefully just leave the gold foils, it looks karat gold so it might even remove much of the base metals from the alloy.
 
I "suspect" that silver "colored" backing/filler is pewter (tin)

try putting a torch to it - tin has a "very" low melt point so will melt off in a heart beat - the residue that stays "wetted" to the piece can then be dissolved away with HCl (if it is pewter/tin)

some of the ones I have seen are resin filled with the pewter backing to hold the resin in place - if they are resin filled you will have very nasty fumes when you torch them

Kurt
 
I have put them in nitric and everything dissolved except the gold foils, foils weight between 0,5 and 0,8 gr each. Processed them in AR and will have a look tomorrow evening at the result. The filling floated on top of the nitric and was easy to remove. Put a piece of copper in it to see if any Silver cements out.
At the piece with 925 or 825 i will have a look later.

Paul
 
Slochteren said:
I have put them in nitric and everything dissolved except the gold foils, foils weight between 0,5 and 0,8 gr each.
Keep in mind that if any of your pieces use pewter as Kurt mentioned, or bronze (far less likely), those are tin alloys, which means metastannic acid when you soak in nitric.

If it were me, I'd file past the gold and test with Schwerter's. Both tin and lead give a yellow color (or yellowish, in the case of alloys with other metals). I'd do so until I was comfortable with the proportion of cheap plated stuff that contained tin.

You may have some patience with metastannic acid. For me, now that I've had to deal with it, I have ZERO tolerance for it.
 
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