Trouble with rose gold plating

"Gold Plating Technology"
by Reid & Goldie
(hard to find & expensive; if you
see a copy cheap, act fast)


on eBay or

AbeBooks

or Amazon

(affil links)

A. Hi. Your question is a bit brief to understand, but yes, rose gold is quite prone to oxidizing because it contains copper. If you can find a copy of Reid & Goldie ==>
in a local or university library it will provide a good education on the subject.

You can follow the instructions on this page for your rose gold, but two points:
• Most professionals do not attempt to formulate their own plating solutions, as explained by Geoff below.
• Because of the copper content in rose gold plating, you may find adding a clearcoat to be a more productive approach than trying to find a rose gold plating solution that doesn't discolor.

Luck & Regards,

A. Could not resist. I believe the only imitation rose gold is called copper :-)
and it has been used (not by my Company) in the past.

A. You can use approximately 1/5 part copper sodium cyanide CuNaCn in your gold plating bath by the percentage of the gold potassium cyanide.

I forget if you like to use a green color in your gold plating you can use a part of cyanide potassium silver AgKaCn in your bath. You must try these recipes in a cell first before you try it in the bath because the recipe is very old. If you don't have a gold bath you can experiment with your brass bath with the current and the contents.

A. Dear Mr. Gutierrez,

I have not found an electroplating process that can produce a rose gold finish which is tarnish free, especially if you are trying to match the color of a cast rose gold which has more of a copper color than gold. It appears that metals deposit as a dispersion and not a true solid solution as in the cast version. This causes the copper at the surface to oxidize in a normal manner. Increasing the gold content can remedy the problem, but you may not get the desired color.

Good luck and if you solve your problem please let us know.

"Gold Plating Technology"
by Reid & Goldie
(hard to find & expensive; if you
see a copy cheap, act fast)


on eBay or

AbeBooks

or Amazon

(affil links)

A. Hi gentlemen. I am not a gold plater, and can only respond from book knowledge and regarding what has been posted on this site over many years. But Reid & Goldie .
seem to imply that the best approach to color gold is to do heavy gold plating from a standard bath and top it off with 0.5µm of color gilding, and they offer the solution composition and operating parameters for an 18 ct pale pink bath and a deep pink-red bath.

Readers have noted (letter 52562 is a good starting point) that the reddish color comes from its high copper content, so you are limited in preventing tarnish.

How about a thin electrophoretic or UV cured lacquer on top of the pink gold?

Regards,

Rose Gold Plating Solution

on eBay or

Amazon

(affil links)

A. Pink, green, yellow, white, rose, red gold are made by adding particular alloys into .995 (23.88k) pure gold to make 9, 10, 14, 18, 22k gold Jewellery. You should plate this Jewellery only those colour in which you cast the Jewellery for better finishing.

A. Hi Hayleigh. We appended your interesting inquiry to a thread which already discusses several aspects of it, but taking them up in the order that you raise them ...

Reid & Goldie seem to suggest that you should plate the bulk of your 2 µm requirement from a more robust standard plating bath, applying only about the final 0.5µm from the more temperamental rose gilding solution. If you can't find tank plating solutions, but have found suitable brush plating solution, maybe that's a better approach.

Immersion plating to anywhere near that thickness is not possible. The 'battery' that drives immersion plating is the difference in electrochemical potential between the substrate and the plating. As soon as the substrate is covered, the battery is dead.

Rather than 2 microns of gold and a "flash" of rose gold that wears off quickly, try the compromise I mentioned that Reid & Goldie suggest.

Rev'd June 10th: I had somewhat misread Reid & Goldie. They suggest that before the 1/2 micron pale pink gilding solution (2 g/l gold, 2 g/l copper, .05 g/l silver), you plate 1-1/2 microns from an 18 carat pink plating solution (4 g/l gold, 2 g/l copper, 2 g/l zinc), not yellow gold as I probably implied.

Best of luck.

Regards,

A. Hi again. Sorry I misunderstood what you intended by "immersion plating".

Generally, high concentrations are used for the main plating solution and low concentrations for the final color gilding. I don't know the capability of those particular proprietary gold plating/gilding solutions, but we do not comment on specific brands or sources in the forum anyway (why?)

Most plating professionals recommend purchasing proprietary plating processes rather than attempting to formulate your own. And once you take that path, you need to follow the technical data sheet provided by the vendor. It is problematical to half-follow the vendor's instructions and half-follow someone else's. "Too many cooks ..." or something like that :-)

Regards,

A. Hi Hayleigh

Home brew processes are the way to expensive sleepless nights.
Many published formulations may have worked once in a lab (if that) and few are reliable production processes. In addition, it is next to impossible to get the chemicals in UK.
Ted is right. Go to one of the major suppliers and you can have practically any colour you want with technical advice a phone call away.
If you are not aware of the major supply houses in UK ask the Institute of Materials finishing (IMF). There is a link on this site or go straight to
www.materialsfinishing.org
You may even consider one of their distance learning courses to understand the process.

A. Hello Hayleigh,
As far as plating options I would suggest the palladium as a barrier plate with the rose gold being your final finish. I must say that being able to plate 2 microns of gold on costume jewelry is virtually unheard of in the industry. Even in the electronic plating industry a little over 1 micron or less is standard. Costume jewelry is normally plated at 3 - 6 microinches of gold. Anyway, if the rose gold flash plate is successful with the palladium undercoat, you should be fine. People that buy costume jewelry expect the finish to wear over time. Have you thought of using a bigger gold plating tank (1-3 gal), and purchasing a rose gold replenisher? You could add a specified amount of the replenisher to the tank per so many ampere minutes or ampere hours plated. If you don't have an amp hr meter you could just track the amp minutes/hrs the old fashioned way (on paper). Amps x minutes plated, for hours divide total minutes by sixty. The replenisher comes in a liquid with a certain amount of gold and copper to maintain a good balance of your desired alloy (color). Your gold supplier can set you up with such a replenisher with the addition rate per stated amp minutes or hours. Good Luck!

A. Hi. I would only add to Marks excellent post the following --
While "being able to plate 2 microns of gold on costume jewelry is virtually unheard of", we should note that 'Rolex [affil links] quality' watches may have 7 microns of gold plating, and top quality pocket watches from a century ago were plated up to 20 microns. It's not that there is extreme technical difficulty with thick gold plating -- it's just that it's not affordable, and that further limits availability.

Regards,

A. Hi Aurelie. More than a hundred years ago we knew how to electroplate pocketwatches with gold so they would last a century. You can still buy such plating on ultra-premium watches. This plating was not high technology; it was just very thick so it took many years to wear away. But you want it cheaper -- and that means you don't really want expensive and heavy gold plating like ultra-premium watches -- you want a cheaper finish that will last a passable time, and just looks good.

The way you can do that is some combination of:
a). gold plating thick enough but not that thick, and/or b). substituting titanium nitride instead of gold as the base layer, and/or c). adding a clear protective coat as the top layer.

A. High quality costume jewelry is sometimes called "micron plating", meaning the electroplated gold is about 1 micron (40 millionths of an inch) thick. A thicker plating than that, 2-1/2 micron, when done on a sterling silver base is called vermeil.

B. Titanium nitride (TiN) and similar gold-tone materials can be deposited by PVD (physical vapor deposition), a vacuum plating process done in rather expensive machines. The TiN is cheap and it is very hard and long wearing, and looks almost like gold. Sometimes a flash of gold is deposited over it.

C. Clearcoats, ranging from lacquer, to UV-curable (like nail-salon nail polish), to automobile 2-component clearcoats, to high technology clear coats can keep wear from getting to the gold.

If the proposed vendor cannot tell you the thickness of the gold -- in fact, if he cannot give you the complete details of what he is applying -- the chances of it enduring several years of constant exposure is nil. You can get a high quality process, it isn't that hard, but it may not match your price point. Good luck.

Regards,

Q. Hi Ted,

Thank you very much for your concise answer.

So If I get a thickness between 10 and 25 microns it should be good quality if I understood you correctly (since the thickness is important)?

Also, if I understood you correctly, Vacuum plated is not necessarily PVD ? It is Ion plating but that can be done several ways right? Or is vacuum plating PVD?

The offer I have right know is vacuum plated thickness between 10 and 25 microns by paying a little more would that be a good quality?

With that thickness, do they also apply an intermediate layer? would palladium be recommended?

Thank you very much for your answer, really helpful!

Regards,

Aurelie

A. Hi again. 1 micron of gold would be quite good quality costume jewelry, 2.5 microns would be outstanding quality. I doubt that you have offers for 10 to 25 microns -- you probably mean microinches. 25 microinches is less than 1 micron (40 microinches), but still probably considered pretty good quality in these days of 6-8 microinches being pretty common :-)

Sorry, I'm not an expert on vacuum plating technologies, so I can't answer detailed questions about them. But PVD stands for physical vapor deposition and, since all such deposition is done in a vacuum to my knowledge, the term probably encompasses all such technologies from the least expensive aluminum vacuum metallizing on shiny mylar balloons through the more exotic technologies on expensive watches. So "vacuum", "ion", and "PVD" are imprecise in terms of what finish is applied and how heavy.

I don't know if they would apply an underlayer of palladium ... I apologize but you can't accept a loose specification from your vendor and then expect a 3rd party to be able to tighten it up. You have to either specify exactly what you want in fine detail and insist upon it ... or you have to get from the vendor the details of exactly what he wants to sell you, and decide whether it's adequate. One thing you might do is have them ship you a few items processed to the spec they propose, and see how they hold up. Me guessing what he wants to do for you from 3rd-hand snippets of conversation isn't going to help much :-)

Buying from China is okay if you are like Apple and big enough to design and oversee production and quality control. Buying from China the way you would like is sometimes cynically called "throwing it over The Wall", which is why the best approach might be to get the samples and hold the vendor to the same quality on your pieces. Best of luck.

Regards,

Hi Geno. You probably know more about the subject than I do, but pure 24K gold is always yellow. Any other color is the result of alloying with other metals such as copper. The more gold, the yellower; the more copper, the pinker/redder. According to the previously referenced "Gold Plating Technology", 18K 4N Rose (pink) gold is 750 parts gold to 90 parts silver and 160 parts copper.

The more gold in solution, the yellower and the higher karat the plating will be, but temperature and voltage (current density) also play a role. There are some theoretical tools like the Nernst Equation that may help us estimate how to shift these percentages, and thus the resulting color, by changing the percentages of metals in solution, the temperature, or the voltage ... but alloy plating is complicated theory and we may rely more on empirical knowledge than first principles. Finally, a brief excerpt from the same book:

Luck and Regards,

Thanks Ted.

Hi John. The formula might be wrong; I see no metal other than gold in the formula, and I was not aware that rose color could be obtained without at least a copper co-deposit -- but I am not a gold plater.

Please introduce yourself and your situation because we don't know if you are an experienced color gold plater wishing to correct this misprint, or a beginner with no gold plating experience ... which could mean a different plating problem rather than a wrong formula being printed in the MFG. Thanks.

Regards,

Hi John, thanks. I wasn't "worried" about your electroplating knowledge, but questions are posed on this site by everyone from 8-year-old children to post-doctural researchers, and it simply helps us all try to answer most appropriately when people introduce themselves.

Regards,

Hi folks. Is it perhaps possible that there is not a universally accepted meaning for "Rose gold"? According to Reid & Goldie there is a standard color "4N" in watchcase plating in Germany, France, and Switzerland which they call Rose (Pink) ... but it has 90 parts silver and 160 parts copper per thousand.

Regards,

A. Hello, I tried to reply, rose gold color can be obtained easily if gold mixed copper with composition 1/3 and must fit.

A. Hi Marina. Unfortunately I don't think there is much that can be said except that the plating and lacquer are not adequate. You could have the parts salt spray tested to determine whether or not they actually survive 12 to 24 hours, but whether they do or they don't, they are not surviving your customers' expectations and needs.

The question for someone becomes "who is responsible for insuring that these finishes are adequately designed and implemented?"

Regards,

A. Hi Marina. Such problems are unfortunately very complicated :-(

You don't know the actual spec for the rose gold plating (how thick it is, what tests are performed to insure no porosity, what chemical analyses are done to make sure the process is under control). You don't know the specs for the lacquer, and whether it is fully resistant to perchlorethylene or other dry cleaning chemicals, or whether any porosity checks are performed on it. You don't know for sure whether the tarnish is due to corrosion, or not.

While swimwear should presumably be able to resist beach and weather conditions anywhere, you don't know the environmental conditions within the swimwear factory in Bali where the ambient air could possibly be laced with acid vapors (I have no idea what chemical operations, if any, are conducted in that factory (do they only do sewing, or do they also do fabric bleaching and such). Are the sliders and hooks exposed to chlorine bleaching as part of the manufacturing process?

Where are the salt spray tests being done? Here in the USA under your evaluation, or is it just the plating shop in China which is claiming that the parts are surviving 38 hours of salt spray and holding up well?

I think you'll need to get a finishing consultant involved if neither the plating shop nor the Bali factory will accept responsibility for doing something wrong. Presumably you are not specifying the details of the plating process but simply buying sliders and hooks which ought to function as sliders and hooks; however, even there, the plating shop might claim that their sliders were intended for dresses not for the rigors of repeated immersion in salt water which swimwear must endure. I sympathize with this knotty problem but, sorry, I don't have easy answers :-(

Regards,

A. Hi Marina
I sympathise with your problem but I would not rush to blame the manufacturer.
A salt spray appears to be an obvious test for swimware fittings. However this will be applied immediately after coating. Fasteners, particularly zips are a very high wear application. I would expect lacquer to have a short service life and the underlying gold will be very thin and therefore porous.
A salt spray after simulated wear would be more appropriate but I fear that the root cause is specifying a cosmetic finish for what would be a challenging industrial application.
Have you considered making the fasteners from a Naval Brass?
It would stand up to salt water much better and have nearly the same colour.