Letter 14022

Gold plating removal [Vermont] 

How (what chemical) can I use to remove the gold plating from an old watch?

Thomas Tomcik
- Burlington, VT

Hi, Thomas. You don't say what the watch case is made of, nor what kind of finish you want to apply to it in place of the gold. So I will guess what you are trying to do and why; I'm guessing you are trying to salvage the gold value of the watch? It's probably a quarter if the watch is from the last couple of decades and a few dollar if it's older. Still interested? :-)

Ted Mooney, P.E.  finishing.com Brick, NJ

My references were in the office. Now I'm there and find that the weight of gold per square foot for each millionth of an inch of thickness is .00147 troy ounces. Say the gold is 20 millionths of an inch thick: that's .0294 troy ounces per square foot. If the gold plated area is 2 square inches (which sounds high), it's .00041 troy ounces of gold. My appraisal of 25 cents worth of gold for a recent watch was on the high side. But we can probably stick with a few bucks for an old watch.

Ted Mooney, P.E. 
finishing.com
Brick, NJ

Hi Tom,

I am going to assume that you are seeking a way to remove the gold from the watch for refinishing purposes not for salvage of the gold. First of all many old watches had good thick plated coatings for longevity. If you are seeking to chemically strip the gold of the watch, it is difficult to do without attacking the threaded and fine mechanical portions of the watch (thin flash plated areas). If there is severe "brassing" (exposed base metal, i.e. brass or nickel, on the wear edges), the stripping chemistry even with buffers will attack the brass severely, long before the thick gold plating has been removed chemically. Chemical stripping is fine for gold coatings 2 microns or less, but you will still have the disposal burden to contend with.

Mechanical removal is the safest using small files and paper sticks. In many cases it is faster than chemical stripping, especially on old pocket watches with 20 microns or more of gold. The filings and "sweeps" can be sent to a refiner for reclaim of the gold. If you do a large quantity of watch refinishing it is worth it.

Hope this helps, Good Luck.

David Vinson Metal Arts Specialties Leonard, Michigan

Mr.Tomcik,

First check out what is the base material. If the base is brass and under coated with Nickel you can strip using Sulphuric acid-glycerol based stripper or sulphuric acid -copper sulphate based stripper. If the base is SS you can strip it with sodium cyanide solution. If a electroplated watch whose effective surface area is between 0.10 to 0.15 sq.dm is plated for 3.0 to 3.5 micron it will have approximately 40 to 80 milligrams of gold.

Venkat Raja   plating supervisor Walkerton, Ontario, Canada

Hello, my name is Paul. I'm a student of Edinboro University of Pennsylvania Art Program. I do some gold, silver and copper plating. Some time I need to recover the gold plated on the "hoops" pieces. I need to know what chemicals I can use with rectifier type gold plate recovery system. We have couple rectifiers in our disposal: one that is 10Volt 80Amp second is 4Volts 5-30Amp, and the third is 6 Volt 10 Amp. This is used for copper plate. I don't want to use sodium cyanide, to dangerous. Is the any other chemical that I can use for the solution to strip gold from copper and stainless steel? What rectifier will perform the best to strip gold from other metals? The left out metal materials are going to be properly disposed, and only gold recovered and kept. Any help will be appreciated. Paul.

Paul Pri
Hobby, Student - Erie, PA, USA

you can use caustic soda its a drain cleaner - available at most leading stores.
I used it on a old watch, it takes about 3 hours..to remove all the gold plate.

thankyou goodluck

Cawnus Smith
- Detroit, Michigan, USA

---
Ed. note: Cawnus is apparently talking about using caustic soda to electrolytically strip gold, not a simple immersion process as only aqua regia dissolves gold.

Hi my name is Bill. I would like to know how I can recover gold from gold plated electronic pin conectores. I have severial pluges that are millaitary grade. Can you help?
Thanks Bill

Bill Bowen
salvage - Decatur, AL USA

Can anyone help....?? I have a pretty rare military cap badge that someone has gold plated for display! The base metal is bronze and my local jeweller tells me that if he tries to un-gold plate it electrically in an acid solution, it will eat the bronze away and ruin his £200 solution and my badge. I have tried to gently rub it off but it's impossible.... any suggestions?

Howard Smith
- Cardiff Wales G Britain

I know there's too much on the internet for any of us to really study, Howard, but re-read David Vinson's reply -- I think it's what you were looking for. You need to find a shop who will mechanically polish the gold off. Good luck.

Ted Mooney, P.E.  finishing.com Brick, NJ

1000 ml H2SO4 in 2000 ml pyrex casserole dish with appx. 1/4 teaspoon of glycerine well mixed into the H2SO4. Submerge a lead bar or rod in the dish with enough of the metal sticking out to connect the negative (-) lead. Obtain a variable power supply (10AMPS MAX) @6-12 volts -- a battery charger works great!). Connect the negative lead to the lead electrode. Connect the positive (+) lead to a cable with STAINLESS STEEL ALLIGATOR CLIP. Attach the item you want stripped to the clip, turn on power supply and lower the piece you want stripped into the acid/glycerol solution. PRESTO--CHANGO! The black residue is approx.
95%+ pure gold. You will need to dissolve and purify product with Aqua Regia or HCL and regular Clorox Bleach (halide leaching. This is simple, safer than HNO3 fumes. I have been using this for years with great success. Good Luck!

Les M. Barnes, LAC
- Carolina Beach, NC

I want to post a question or inquiry of my own.

 

I want to answer or follow-up on this question publicly (in non-commercial fashion).