Letter 28017

Need info on very thick gold sulfite electroforming [Canada] 

++++ Hi, I am an artist/goldsmith and author. I want to build a gold electroforming bath using gold sulfites (potassium or sodium?). I understand that stability of these solutions is fussy and they need buffering with sodium sulfite. I would like to be able to electroform to .5 to 1.5 mm thicknesses. I do not care about nodule formation, in fact I would like that. As well, a bright finish is nice, but not necessary as I can tumble the finished gold objects. I would like to be able to make up bath replenishing solution myself if possible to lower costs. Can anyone advise me here? What formulas, equipment etc are specific to doing this with sulfites? How tricky is it to maintain the bath? I do not care how long it takes to grow the metal (well, within reason).

Thank you,

Charles Lewton-Brain
Artist/goldsmith/researcher - Calgary, Alberta, Canada

Dear Charles!

Gold sulphite bath is not something for Do it Yourself work,but i think you can use ferrocyanide bath (0,5-1% of potassium cyanide toxicity). I am metalwork conservator and we used it for silver electroforming and it works.

Potassium ferrocyanide.....200 gm
Potassium carbonate.......40 gm
Gold chloride............. 50 gm
Water......................1 lit
stainless steel anode,or platinum plated titanium (never mix solution and acids)

Goran Budija
- Zagreb, Croatia

Charles,

In the early 70's, I worked for Sel-Rex, the first maker of sulfite gold plating systems. One of the many things that I was in charge of was the manufacture of sodium gold sulfite. The process is dangerous - maybe even more so than the cyanide you're trying to avoid. There are bad acid fumes and, at one point, there is a great danger of producing the extremely explosive gold fulminate. Besides this, the process is tricky, exacting, expensive, and requires a good production chemistry background. The process was patented in the late 60's. The patent is about the only place that you'll find out where to make it. No one is going to tell you how.

Do the smart thing and buy the solution ready made. I would strongly suggest buying from Technic. They have always been innovative and helpful and they know as much about sulfite gold as anybody. Ask a lot of questions. Make sure the bath will plate to a thickness of 1.5 mm (.059"). Sulfite gold is not that easy to use. When things go wrong (and, they will), you'll many times need the free (usually), instant, expert advice that ONLY a supplier can give you - that's what you're paying for. Plus, you'll end up with a better, more reliable system. It's usually penny-wise and dollar-foolish to try and make your own chemicals or solutions, whether you're plating gold, nickel, silver, or whatever. Only amateurs do this, thinking that they'll save money.

A cyanide solution, containing about 4 tr.oz. of gold per gallon and using gold anodes, may still be the best (and, cheapest - and easiest) choice for electroforming gold. Technic, or other good gold bath suppliers, could sell you the PGC, give you a good bath formula, and tell you how to set it up and use it. Cyanide is safe if you know what you're doing and do it legally. It's not something you do in your garage. Check out thread #25979, read plating books, and search for other cyanide info on this forum and the internet. Be prepared.

Otherwise, find a plater. For small volume, this is your best choice. However, it makes experimentation more difficult.

Chris Owen
Consultant - Houston, TX, USA

"Only amateurs do this, thinking that they'll save money." Great point, Chris. My 9 years of running this site reinforces that professional platers know better than to try to design their own process chemistry, but amateurs don't.

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

Hello Charles and plating colleagues, normally I would agree wholeheartedly with the advice given to "amateurs" embarking on this journey called electroplating. However, Charles is no amateur in the sense often used in this forum. Mr Lewiston-Brain is an accomplished technical researcher and practicing goldsmith. He is internationally recognized for his efforts in raising the safety awareness for practicing artists to the wide array of health hazards often encountered in the field of goldsmithing, sculpture and jewelry. He is highly regarded within his field and has provide accurate and easily understood information to anyone who would listen, especially educators. I have no doubt he will safely find a solution and methods to meet his requirements.

Charles, you are on the right track with regard to sulphite based gold chemistry for electroforming. Avoid the ferrocyanides, re mediation is not good for this family of chemistries. As mentioned,there are commercial chemistries you can purchase that will meet your needs. Contrary to popular belief there are few people left within those companies mentioned that have the "actual" intimate and direct information (gold electroforming)based on empirical discovery which could help you. However,they can provide general principles and guidelines to follow if you can locate the right person. Other elements that will be critical to your success will include selecting the correct power supply, temperature and metal density of gold bath, agitation as well as numerous other variables which will need to be included. The cost for procuring the equipment, chemistries and the time to bring all the esoteric elements together is no small feat even for the accomplished plater. A very high degree of process control and bath monitoring is essential. You are probably familiar with the remarkable work of Stanley Lechtzin with regard to electroforming with copper. You will find that gold electroforming is significantly different (tougher)in chemistry, correct waveforms,and as you know costs.

If we have not collectively discouraged you yet, contact our company using our sponsored link and I will provide you a "roadmap" that may help you decide best methods, formulas and resources that will assist you in meeting your requirements. By the way, try contacting Neil Bell from Red Sky Plating as he also has expertise on this topic and has been consistently generous and gracious with his knowledge.

Best regards,

David Vinson Metal Arts Specialties Leonard, Michigan

It was a bad choice of words as I am in awe of how metal-working artists do what they do. I should have said that people who have done a lot of electroplating usually understand the advisability of using proprietary chemicals, whereas people who haven't done plating often don't even know that this is the customary approach, but assume that plating solutions are customarily made by the user from raw chemicals.

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

Dear Charles!

I have used ferrocyanide bath over 10 years and I can tell you that it is very stable and easy to prepare.I have used it for gold plating ,not for electroforming (2,65 gm gold chloride,15 gm potassium ferrocyanide,15 gm sodium carbonate/for electroforming bath must be concentrated).

From financial point this type of bath is much cheaper than any proprietary product and, last but not least, several good books mentions it: Lowenheim's Modern Electroplating, 1963, Dettner/Elzes Hanbuch der galvanotechnik/1963. If you don't want to work with it simple chloride based bath is also one possibility.

Chloride base bath:
gold chloride.......25-40 gm
HCl(1,19 gm/l)......20-50 gm
sodium chloride.....10-30 gm
H2SO4(1,84 gm/l)....10-20 gm
water................1 lit
temp.................70 C 8-10 A/dm2

Good luck!

Goran Budija
- Zagreb, Croatia

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