Gold stripping cell

[Williamjf77]

Hello I had a question about stripping gold plating.

Is it possible to strip gold filled jewelry in a sulphuric acid stripping cell?

Does anyone do this or is the preferred way to treat with dilute nitric acid?

Thanks

 

[FrugalRefiner]

A stripping cell will struggle with gold filled for two reasons.

• Gold plate is nearly pure gold, and the stripping cell is very effective at attacking pure gold. Gold filled is a gold alloy on the surface, so the gold is alloyed with base metals like copper, silver, etc. which are not attacked.
  
  The layer of gold on gold plated items is very thin, so the stripping cell can remove it fairly quickly. By comparison, the layer of gold on gold filled is very thick, so even if it were pure, it would take a long time to remove it.

Nitric is effective and fairly fast at dissolving the base metal, but it can be expensive and difficult to source for many. Some people use CuCl₂ (often referred to as AP) leach to dissolve the base metals. It's much slower, but HCl is cheap and easy to find.

Dave

 

[Williamjf77]

Thanks for that explanation.

So if some broken jewelry which was believed to be just gold plated got put into a stripping cell but was actually gold filled it should be noticeable?

 

[FrugalRefiner]

So if some broken jewelry which was believed to be just gold plated got put into a stripping cell but was actually gold filled it should be noticeable?

That's hard to say...

When "gold filled" was created, they would fuse (~solder) true alloyed sheets of karat gold to thicker sheets of base metals creating a sandwich with karat gold on the outsides (the bread) and base metal filling (the meat) on the inside. The sandwich would be rolled into a thinner sheet, and items would be fabricated from this raw material.

Things have changed.

Now, I see things like a men's ring stamped as 1/20 12K GF. There is no way that such a piece is made from a sheet of traditional gold filled. In the US, the standard is based on the percentage of gold in the item. If an item like a ring is marked 1/20 12K GF, it is legal as long as the percentage of gold is 1/40th of the total weight of the piece. Gold filled still implies that the metal on the outside is a karated alloy of gold and base metals, but how manufacturers achieve that goal are probably closely guarded secrets.

My main experience with gold filled was in my early days making jewelry with gold filled wire. That wire was made in the traditional way, with a tube of hollow, karat gold fused to a rod of base metal fitted inside the tube. The wire was then drawn and rolled to the desired dimensions. When processed in nitric acid, the base metal core dissolved, leaving thick foils of 12 K alloyed gold.

Whether a piece of current gold filled jewelry will be obvious after stripping may depend on the particular piece and how it was made.

Dave

 

[snoman701]

I wouldn't mess around trying to use a stripping cell with gold filled.

The stuff is always filthy. My first step is to cook it to burn off the grease. Then once it's been cooked, the gold is actually sort of absorbed by the copper/brass/base metal base. This won't strip well.

The cell shines on things like gold over nickel.

I've been running a bunch of gold filled with nitric lately. Wickedly simple once you figure out how to filter it well.

I've been doing 200 gram batches, but honestly it's boring. Switching up to fill kg batches from now on.


Sent from my iPhone using Tapatalk

 

[Williamjf77]

Thanks for all the info, really I was pretty sure you couldn’t or shouldn’t use gold fill led in a cell but was curious.

What do you do with a pile of unknowns though? Without testing everything or inconclusive tests for gold filled vs plated?
When in doubt go to nitric because even if it’s plated it will still do the job?

Thanks

Will