Color gold/color gilding: Rose/pink/brown gold plating methods & issues

A. Hi Jagadish.

I believe you are right that you need copper for pink or rose gold. But gold is naturally yellow, and gold coloring is a craft, an art, and a trade secret more than a science, so I don't think you will find complete, proven, working recipes which require no tweaking, or no maintenance based on experience.

Styles change, but when I was younger "tri color gold" (rose, pale green, and yellow) was all the rage in the USA and I visited the plating shop of the manufacturer who produced it. I got the impression that only the foreman, not even the owners, knew all of the secrets -- so don't expect it to be super easy :-)

Still, there are at least two good text books on the subject which should be an excellent start. They are probably available in a university or technical library in or near Bangalore. Good luck.

Where did you get the formula you are currently using?

Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Gold coloring is a treasured art form that I don't pretend expertise or experience in, so I hope you can get an authoritative answer from someone. But in the meanwhile, Alfred Weisberg's handbook article on the subject, which can be found in older issues of the "Metal Finishing Guidebook" or the "Products Finishing Directory", gives charts of the various colors and the percentage of copper and nickel, etc., used to obtain them. Best of luck.

A. Hi,

I think this problem is of more copper content in the bath than what is recommended. So please reduce copper content in your bath; meanwhile maybe there may be a cause: if pH is too high this problem arises. Check the pH of your bath and then if bath contains organic contamination, that also may be one of the problems.

A. Hi, Abhishek I don't have a definitive answer for you, but we appended your inquiries to a thread that at least offers good hints. Good luck.

A. Hi, Jayalakshmi. The term "gold coloring" using means a thin topcoat of gold plating in a different color than 24K gold, and is done by that final gold plating layer alloying other metals into the plating.

in general, copper gives a pink to reddish cast; silver or tin a greenish cast, and nickel a Hamilton to whitish cast. You will find some general introductory info about this subject in the Metal Finishing Guidebook, but Reid & Goldie's "Gold Plating Technology" has a chapter or two on this subject and there is also a whole book available just on this one narrow subject ⇨
Even still, you may find the subject to be more within the domain of art than science, with exact formulas rather closely held.

But Good luck.

A. Hi, Joseph. Rose gold / pink gold is available on line. Amazon has a couple of brands, and eBay has more than half a dozen [adv: Rose Gold on eBay or Amazon [affil links]

Al Weisberg's "Gold Plating" chapter in older editions of the Metal Finishing Guidebook has a lot to say about what plating parameters to vary to bring out different tones of reds and pinks, and should be worth a read for this.

I have skimmed but not studied Reid & Goldie's "Gold Plating Technology" for this subject myself, and it has a lot of the info you need, like what shade each alloy metal drives the plating towards, a list of the standard colors in watchcase plating, etc.

Technic and DeGussa are probably the major suppliers of precious metal plating processes, and can probably provide some pink gold plating solutions. Good luck!

A. Dear Rose (et al),

Red gold alloys have a very high copper content and will form a heavy oxide when heated in air. A few suggestions may be helpful in minimizing the oxidation;

1. Apply a protective fire coat of boric acid ⇦this on eBay or Amazon [affil links] and alcohol with a brush to the entire surface of the piece. Dry the coating with a soft torch flame before soldering.

2. Use a softer reducing flame (slightly richer in gas than air or oxygen). This will reduce the amount of oxide formed during soldering.

3. Try using a paste type soldering flux instead of the liquid solder flux. It will provide better protection during soldering and won't burn away as fast as the liquid fluxes. Apply more flux if needed during the soldering process.

4. The red gold solders have a very hard flow. Be careful heating the piece during soldering to avoid melting the piece you are soldering.

5. Pickle the soldered piece in a hot "Sparex" safety pickle (sodium bisulphate) solution. It may need a longer pickle time than normal to remove surface oxides.

A good source of excellent shop information for jewelers and jewelry manufacturers is "The Orchid Website", easily found on your search engine.

Good Luck & Best regards,

A. Pink gold contains copper, your soldering removed the copper. I'm not sure but if you tried brushing with a copper soft brush, you may have some reddish color, otherwise you may consider plating.

Good luck

A. Are you talking electroplated gold or fine gold castings here? To achieve a pink or rose gold color the copper content in the alloy is more prevalent than normal alloying metals. In your region copper would not fare too well because of the weather conditions there. Is it possible that you could apply a clear lacquer coat to the jewelry for finish protection?

A. Two problems: (1) "Rose Color" is too low an alloy to resist tarnish but a higher "karat" would not be rose. (2) The silver migrates right thru the gold, you must have a diffusion barrier between the silver and gold: either nickel or palladium.

A. Carrie

A couple of important questions. What thickness of gold did you ask for and what thickness did the plater supply?

Many jewelers request a 'flash' of gold for costume jewellery. The plating industry understands this to be enough plating to just give the colour required but too thin to be practically measured. The gold is so thin that the underlying metal readily corrodes. See thread 52510.

If this is the case, you should recognise that the price you pay is mostly for the process of plating as the actual gold you are buying is very little.

I suggest that for a quality product you will need about a micron of gold and the base metal items will require an undercoat - possibly silver or palladium as nickel is not permitted in many countries for skin contact applications.

A. Hi,
there are two reasons of tarnishing rose gold deposition on silver. First reason can be insufficient thickness of the deposition. If the deposit is a very thin, decorative flash of gold or alloyed gold we can observe migration/diffusion of silver atoms into gold in few weeks or even in few days. The gold deposit on silver must simply be thicker or have a diffusion barrier. The second reason can be the wrong gold plating process resulting mostly in low gold concentrate in the alloy.
Regards

A. Hi,
I fully agree with the all above suggestions. Alternate way you can go for trivalent gold base rose plating or incorporate the anti-tarnish after rose gold plating.

Regards,

A. Hi, I've 37 years experience gold plating all sorts of different components. Amongst others, I used to manage an 18 ct rose gold process. We made, polished & plated corner mounts for a very well known luxury product company. The spec was 2.5 microns of 18 kt gold followed by 0.5 microns of 23.5 kt 3N.
Any customer requiring a top coat finish of 18 kt we would simply nickel, 3N gold flash, platinum 0.1 microns, 18 kt rose gold and finally immerse in an anti-tarnish solution. Worked every time for us on thousands of parts. Hope this is of some help to you.

A. Hello Lynn,
You had mentioned that the ring was kept in its case and 9 days later it was discolored. There appears to be a problem with the plating deposit. This could stem from a few things. The alloy of the gold bath was way off, the gold plating was too thin, and migration through the gold plating occurred. It seems to me the plater would have masked off the white gold portion, and selectively rose gold plated the "stripe". If this was the case, discoloration due to thin plating would be a lighter gold color, not reddish. From what I see from the photos it seems the gold deposit contained too much copper, which is the main alloy for rose gold plating solutions. I was never a big fan of gold electroplating on wedding sets. Gold plating does not last very long when rings are worn every day.

A. Hi Padmanava. Is there a typo in your inquiry as you mention 24 ct in your title and 20 ct in the text? I don't see how 24 kt gold can be anything but pure yellow, although I'm no expert.

3N is Yellow, 4N is Rose (Pink). The previously referenced "Gold Plating Technology" [on AbeBooks or Amazon affil links] by Reid & Goldie has whole chapters on the topic of gold coloring / color gilding / watch industry applications. Good luck.

Regards,

A. Hi again, Padmanava.
"3N" is the color of an 18 ct gold which contains 750 PPT (parts per thousand) gold, 125 PPT silver, and 125 PPT copper.
"4N" is the color of an 18 ct gold which contains 750 PPT gold, 90 PPT silver, and 160 PPT copper.

Whether your supplier's gold plating solution can produce a 3N and a 4N color through changing some simple parameters is something that I would not know. I have no idea of its composition, and there are countless formulations. For the same reason, I don't know the suggested operating parameters for your supplier's gold plating solutions. You have to get this information from them. Sorry.

If you know the general constituents of the gold plating solution, the Reid & Goldie book might help ... I tried to give you the most essential info but it is 630 pages, and not something I can summarize in a paragraph or two. Get to the library :-)

Luck and Regards,

A. Hi Pratap,

An acidic gold strike (between silver substrate and rose gold) at low cathode efficiency (~20%) is recommended to improve silver-to-gold adhesion.

Regards,
David

Hi Pratap,

Yes, alkaline pH is a concern. There's 22 carat gold/palladium/copper alloy at neutral pH (~7.0) available in the market which produces rose gold color. You may consider.

Regards,
David

A. Couldn't help but notice that the last two posts are questions which they answer themselves!
Q1- First Ankit if it appears to be a translucent red paint over a gold metal it is possible that is all it is. There are several paints and lacquers that can be dyed then applied over gold or a gold plated substrate. If you are simply seeking information on the best dyed organic coating for gold I would suggest you begin researching any and all information you can find on E-coating. Thankfully there is quite a bit right here so you don't have to go far to get started.
Q2- Reza, If you are looking to achieve a copper toned gold then what you would add to your gold plating solution is exactly that: Copper. Most in the world of plating will refer to a copper alloyed gold bath as a rose gold bath. if you use a gold provided by a supplier, ask your supplier what copper additive is compatible with your solution. It's debatable what the right concentration of copper is, but I have found the best results in color tend to lay in the 400-600 PPM Area.

A. What you want to do is quite conventional, but unfortunately its life probably depends drastically on the exact application. It would probably last many years on a broach but fail on a ring in a week or two.

I hate to suggest a clear coat on the high quality jewelry you are making, but perhaps it's the alternative. Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey