PDA

View Full Version : Non-cyanide silver electroforming



MMM Jewellery
03-02-2014, 02:22 PM
Hi
I have seen a few older posts on this subject but none seem to answer my questions:
I'm experimenting with electroforming at the moment and i have had a few good results with copper. I'm now starting to look at silver electroforming.
I see Cooksons sell a silver solution suitable for electroforming but on reading up on the data sheet over at your new boss's site (Heimerle + Meule) I see that it is cyanide based, which is not ideal. (incidentally, I am amused that people wouldn't countanance using cyanide but will happily use sulfide based patina solutions, despite hydrogen sulfide (300-350 ppm) and hydrogen cyanide (100-300 ppm) having almost identical LC50 values!)
So my questions are:
-Does Cooksons sell a non-cyanide silver electroplating solution? If not I'll try some of the specalist groups out there- SPA plating seem to have one.
-Are the non-cyanide silver electroplating solutions suitable for electroforming? I've not been them mentioned in this context when reading up on the subject- only as plating solutions.
-Can you use a fine silver sacrifical anode with the non-cyanide solutions to avoid depletion of the silver from the soution (which I believe is the case with cyanide solutions, but correct me if I am wrong) They often seem to recomment a stainless steel anode.

If I can't get no satisfaction I will try just silver plating my copper electroforms- which is probably the low hassel way of doing things!

Thanks for your help.

Matt

Dennis
03-02-2014, 03:28 PM
I'm not sure of the answer Matt, but a number of the so called plating solutions are just dips designed to cover patches of wear on silver plated items, such as for instance cutlery.

As they work electrolytically on base metals and cease to function as soon as the exposed surface turns silver, the coverage will be very thin and virtually an illusion.

I do know that even thickly covered, electroformed items can be very fragile and need a decent shell. So yes, it's best to send them away to a specialist company.
However you look at it, you won't survive breathing in hydrogen cyanide.

Regards and welcome, Dennis.

MMM Jewellery
03-02-2014, 04:08 PM
Thanks for your reply Denis

I am specifically interested in the electroplating solutions, rather than the electrochemical ones you mention- there are new non-cyanide ones out there now, so surviving hydrogen cyanide is not an issue anymore. I belive the counter ions are succinamide (recent) or sulfur based (available since the 70s but not used much) which have lower toxicity and should be low risk for hobbyists like myself- I guess I'm looking for someone with experience with the new generation of electroplating solutions.

My experiements with copper electroforming are actually quite robust- I have exerted considerable pressure between thumb and fingers without flexing of the form- comparable to 1.2 mm silver sheet for instance. That took about 6 hr to build up, so silver should be doable too- maybe with a couple of light copper coats in the middle to generate alloys and help with hardness.

Thanks Matt

Dennis
03-02-2014, 09:15 PM
Well, the if you find what you are looking for, I hope you will share your results with us here. Dennis.

ps_bond
04-02-2014, 07:27 AM
I've just checked through my references and I'm afraid all I've got is on using cyanides.

ps_bond
04-02-2014, 07:48 AM
A 12-year-old paper on CN-free plating solutions:

http://www.istc.illinois.edu/info/library_docs/rr/RR-94.pdf

Not the most cheery reading.

MMM Jewellery
04-02-2014, 09:41 AM
Hi
I have found this at metalfinishing.com from 2012, which in part answers some of my questions- you just need to look!! The product is from Dow and aimed at the electronics market but is probably ok for jewelery too- they have an photo example for decorative applications. Things have moved on in the past 12 years :)
"SILVERON GT-101 Bright Silver, an improved cyanide-free silver electroplating bath, has been recently commercialized. A series of successful industrial installations have demonstrated that the silver deposits obtained from the SILVERON GT-101 bath are suitable for a very wide variety of applications. The present article describes the characteristics of the deposits from this cyanide-free, alkaline silver electrolyte in comparison to those obtained from conventional cyanide silver electrolytes.
-Cyanide-free electrolyte
-Suitable for barrel, rack and reel-to-reel plating applications; with a maximum applicable current density slightly lower than that of cyanide electrolytes
-Highly stable electrolyte and consistent plating performance under production conditions
-Fine grained, bright, white silver deposit suitable for a variety of applications
-Good silver adhesion onto copper or nickel based substrates
-Low contact resistance, excellent good solderability and ductility
-Suitable for Al- and Au-wire bonding applications
-Good reflectance at wave lengths between 400-450 nm; with evaluations for LED applications in progress
-Increased deposit hardness, but comparable wear resistance to that of silver deposits from cyanide electrolytes

They also mention:
"Generally, soluble silver anodes are recommended for production, so that replenishment of metal salts during production can be avoided." - So that is one of my question answered

Now all I need to do is track some down in a less than industrial quantities!! And have a peak at the MSDS. I might just have to do the electroforming experiment myself, but I cant see it being problematic. I'll see what other brands are available and post accordingly.

Cheers Matt

ps_bond
04-02-2014, 10:29 AM
Gah... Started writing a response then misplaced it. Oh well.

I did see the releases on GT-101, but hadn't seen anything on how it behaves in thicker applications. Lower current density is a boon though.

I was going to ask if you had a copy of the Electroforming book by Leslie Curtis - then I saw this: http://www.amazon.co.uk/Electroforming-Jewellery-Handbooks-Curtis-Leslie/dp/B00DJFLN86
Well, that's my laugh for the day...

MMM Jewellery
04-02-2014, 11:23 AM
Thanks- I have seen the book cheaper on the US site but I'll resist the urge for now to part with that much cash.

Chestech seem to be the UK supplier of Dow plating solutions so i'll give them a call and see what sizes they do and if they'll sell to me. SPA plating also do a silver plating solution that is cyanide free but I will need to write to them to see what the make-up is and how it performs for electroforming-it would be a suitable option if I wanted to silverplate my copper electroforms at least.

I was wondering if Heimerle + Meule do a cyanide free plating solution- do Cookson have access to their plating section or is that sort of integration not happening yet?

Cheers Matt

MMM Jewellery
06-02-2014, 09:55 AM
Hi
I have heard back from SPA plating, but not yet from Chestech. The SPA system uses silver sulphate, I have also found Rio Grande do a solution called Midas that uses silver succinimide (it had only one poor review on-line, highlighting poor adhesion and dull finish). I have not yet got a Dow MSDS to see what they use.

Here is the reply from SPA:
Thank you for your enquiry. I have tested the solution with a silver anode and it works fine.For optimum results, the operating pH of this solution should be kept within the range 7.5 to 10 using a pH meter.You should be able to get at least 4 turnovers of silver (100g of silver per litre of solution) before the solution needs replacing.I have not tested it out for electroforming yet, but do not think that it will be suitable as the deposit is quite highly stressed.The best sort of solution for electroforming is one containing cyanide, but due to the high level of cyanide,we are not prepared to market such systems.

Mate
09-06-2014, 08:52 AM
Hi,
Did you find/try good silver plating bath? Ready made or just solution recipe?

MMM Jewellery
09-06-2014, 12:20 PM
Hi
The only available solution in the UK that I found was silver sulphate which you can buy readymade from SPA plating- it is not suitable for electroforming and I have had variable results with electroplating (I think you need a very big anode surface, sometime the plate would be shiny and good, other times it was furry and white- I need to do more of a play with it, e.g I haven't checked how thick I can get the plate). I have been electroforming in copper sulfate, giving a quick wash with distilled water and then electroplating in the silver sulphate solution. Afterwards I fuse and anneal the whole object at near the mp of silver to burn out the mandrel and smooth out the dodgy silver electroplate; you can see the results on my FB page: https://www.facebook.com/MMMJewellery
It is in an album called electroplating experiments where I was plating leaf skeletons. Hope this helps
Cheers Matt

Dennis
09-06-2014, 02:42 PM
A huge body of work, which I admired, but what I envy most is a decent sink in your workshop. Dennis.

Mate
10-06-2014, 01:48 PM
Thank you for your reply. Your leafs looks good. I will need to silver plate mirror like polished copper plates. I thought it would be cheaper not to buy a ready made bath. I was readying many patents about silver plating. I found informations about succinimide, thiosulfate, 5,5-dimethyl hydantoin and about potassium iodide based baths. Did you read about them as well?
For me succinimide based bath was the most promising. I bought the ingredients, but before the first try I found an article about stability problems. 5,5-dimethyl hydantoin is in the most recent patents but no information about how to maintain. Thiosulfate: poor adhesion... Potassium iodide: If I wont have success with succinimide, I will try this, but not much informations about bright silver plating with this.
Do you have any information about any of them?

Tabby66
10-06-2014, 02:54 PM
You have some beautiful work there Matt, it looks like you enjoy trying out different techniques, and with quite some success!!
Though I have to say, I'm with Dennis, I too have 'decent sink in my workshop' envy

MMM Jewellery
10-06-2014, 07:41 PM
Hi
I did look at those variants (although the potassium iodide one is new to me- I would expect silver iodide to precipitate out: AgI Solubility in water 0.0000003g/100mL (20 °C))You must have a good chemical supplier to get the raw materials!! I did look briefly at buying the raw materials but gave up. My concern with these new baths is that the manufacturers will add a brew of other components to maintain the bath and deliver the desired results- these may not be disclosed in patents. If you don't have the succinimide solution hanging round for a long time you should be fine- my guess is that it will last a few weeks (even a few months) without to much degradation.
Let me know how your experiments work out, and good luck.
Thanks Matt

MMM Jewellery
08-08-2014, 09:38 PM
I have found more info on the silver sulfate bath, the additive is ammonium carbonate 5g to 15g silver sulfate (or also quoted 70parts ammonium carbonate to 156 parts silver sulfate). This bath is not good for electro forming or even thick plate as the silver is stressed and becomes white and flaky. I have not seen any other solutions for this other than cyanide ones.

P.s thanks for the kind words regarding my work, it is much appreciated. I agree that it's a luxury having a sink-I went to some effort to ensure that went into my shed! !

coffejohn
06-05-2015, 01:30 PM
I am also looking to electroform in silver having done so in copper. Having used cyanide based solutions some years ago to plate in brass I see no issues with it as long as you wear rubber gloves and work in a ventilated area.

Having used conventional plating power sources I now use a pulsed power supply; just a conventional supply with an electronic switch on the supply to the anode. This gives faster plating and smoother surfaces.

If anyone wants the construction details just shout.

trialuser
06-05-2015, 03:22 PM
I'd be interested in the pulse switch, I like to tinker.
Cheers

coffejohn
22-05-2015, 07:24 PM
It`s pretty straight forward really, just a case of putting an electronic chip ( a 555 timer chip driving a suitable power transistor/power control unit ) into the power supply to the anode. For high power plating a reverse pulse is applied every 5 or so pulses but for low power plating this can be dispensed with.

Any site showing details of the 555 chip will provide all the details you need The trick is to use a suitable power transistor, power control unit, to switch the anode current. I use an H-Bridge module such as a L298N ( I tried to provide links but was unable to do so as I have yet to reach 5 posts).

If you get into it let me know how you get on. Next time I should be able to posts links to show details of circuits etc.

Regards john

ps_bond
22-05-2015, 08:56 PM
Any particular reason for not using an SSR off a 5V line?

coffejohn
25-05-2015, 01:39 PM
Not technically as far as I know, may be overkill though but if you have one try it.
The advantage of the L298N is that if you choose to use reverse pulse later it is set up for that purpose. A useful site for the L298N is: http://www.instructables.com/id/Arduino-Modules-L298N-Dual-H-Bridge-Motor-Controll/

The deciding factor is the switching rate; I use 200 cps at 50/50 on off ratio, but if you like experimenting you can go up to 30-50kps.

jeweler
06-10-2015, 10:24 AM
It seems there is no instruction or much literature out there for electroforming silver directly onto conductive paint treated surfaces. I have started now with the Cooksons Scandia 360 cyanide silver plating solution, working on an outside bench in a large tray and proper respirator mask, painters jumpsuit and gloves. Even though even the rinse baths are slightly alkaline you can still smell the cyanide fumes without a mask. I think, working with my chemist background, this is safe. The items, a flower and a mushroom, sprayed with conductive paint, came out with a bright grey matte coat, not shiny. They quickly turn yellow and darker, too at some places. There should be a plating time or 2 minutes per 1 micron, so I gave the items each 1 hour, which should be 30 microns.
The petals of the flower are stiffer, but not really enough to be taking any larger force like polishing. I left the item in one hour more and there is only small change, definitely not 60 microns! Because the plating solution is black, you can't see what is going on inside the beaker. I use 6 fine silver electrodes each 30g. The rectifier has been set to 1V and then to 0.01A/cm2, but the current is fluctuating a lot and it wasn't possible to increase it to the needed level of 0.9A for this item without turning the voltage knob up, too. This direct silver electroforming is very different to both copper electroforming and silver plating on a standard ring, I can say, so far. If anyone has tips? I suspect the electroforming times are much longer than the standard recommended plating times, so not 1 micron per 2 minutes. I suppose it is more similar to electroforming copper where you should have a lower current to start with and then increase and leave for hours? Right now I think, electroforming copper, nice and shiny and then silver plating is much easier. But is the resulting item fine jewellery or costume jewellery with so much copper? What are your ideas?

ps_bond
06-10-2015, 10:45 AM
Just looked up the numbers in Electroforming; according to that, the deposition rate @ 0.5A per square decimetre (eww) in cyanide silver is about 19u per hour. 1A/sq decimetre it lists as approx 38u/hr at 100% efficiency.
The chart doesn't go beyond 5A/sq decimetre.
If your PSU is delivering fluctuating current that's unlikely to help things.

Dennis
06-10-2015, 11:37 AM
The electroformed silver remains porous, which means that articles which decompose, will also discolour it. On the whole, it is better to choose dried objects, which will dry again and form a matrix, however weak, for the piece formed.

There is little hope of polishing beyond say, brushing with a glass brush. Heavy deposition is at the expense of detail so except as a curiosity, I don't find much use for this process in jewellery making.

MMM Jewellery
06-10-2015, 11:53 AM
Thanks for the update!

I'd love to see your neighbours faces when they see you out and about with all your gear on!! As a chemist myself, I cant say I am as sanguine about the risks- your precautions are good but it is the mistakes/errors that hurt and with cyanide you only have 1 minute to save yourself.

Having not used the cyanide solutions I can't give expert advice, but from my reading about, I thought you needed to use a strike solution first and then electroplate over that. Also, do you have any agitation? That often helps things. Further to Dennis's note did you seal the objects first with an acrylic sealant?

WRT the finished product- if it is hand made and good quality then it as a piece of artwork, irrespective of the materials. Probably couldn't call it fine jewellery mind you.

Cheers Matt

John Mitchell
12-01-2016, 02:45 PM
Gah... Started writing a response then misplaced it. Oh well.

I did see the releases on GT-101, but hadn't seen anything on how it behaves in thicker applications. Lower current density is a boon though.

I was going to ask if you had a copy of the Electroforming book by Leslie Curtis -
Well, that's my laugh for the day...

That book is eye-wateringly expensive, but I found a second-hand copy on Abebooks for a shade over £30- always worth a look...

John

ryanthomasparker
28-08-2016, 06:38 PM
Apologies for resurrecting this thread, but I can't seem to find any more info on what has been discussed here prior.

I am interested in building a pulse controller like the one described by John (555 timer based) or some alternative. Has anyone explored this further? I understand conceptually what the unit needs to do, but I am unsure of how to build it. Having experimented with pulse plating a bit, a small low cost DIY chopper circuit like this seems like it could be really handy.