PDA

View Full Version : Silver clay disaster! Please help!



KJS
17-08-2015, 04:37 PM
I've been running a fingerprint jewellery business for about three years and although when I began I had some issues with the backs breaking off cufflinks, that was resolved and I've had no problems since then. Until recently that is! After making lots of cufflinks for Fathers' Day I had a few returns where the backs had broken off only in a different way from before. Rather than a clean break leaving a cufflink face that I could sand down and start again, this time small amounts of the silver from the back of the cufflink face had come away leaving a little pit. What was inside looked like unfired silver clay which suggested that the kiln had been underfiring. I spoke to the man at Prometheus and emailed the manufacturer in Turkey and was advised to recalibrate it and buy a new thermocouple which I did. Today I soldered a couple of cufflinks that I made since recalibrating and installing the new thermocouple. I gave them a good pull afterwards to make sure they were connected but again one of them broke and again taking away some of the silver. I was baffled and wondered if the cream coloured powdery looking interior that had been revealed really was unfired clay so I took a wire brush to it and after brushing it looked silver. So I'm really confused. At this point I don't feel I should take any more cufflink orders and considering they make up a substantial part of my sales I don't know if I can even carry on with the business unless I get to the bottom of this. If there are any experts out there or people who've had a similar experience I would be so grateful to hear from you! Many thanks :)

Dennis
17-08-2015, 06:10 PM
Without offence I would urge you to abandon fired clay articles for sale, because the result is difficult to predict.

Once you have made your prototype, send it to a caster, who can make and cast multiples from it and return them with a degree of finish if required.

Your life will be worth living again. Dennis

caroleallen
17-08-2015, 10:02 PM
I don't think anyone on here can answer your question properly as not many of us use clay. All I can suggest is that you fire it for longer than you normally do. I know a lot of people use it for fingerprints and I've done a few in my time. I've never had the problem you've been having though. Do you burnish the clay before soldering on the back? PMC is quite porous and you need to harden it. You also need to use a lot more solder than you would for sterling silver as the clay soaks it up.

KJS
17-08-2015, 10:33 PM
Thank-you both for your replies. I've been making and selling silver clay pieces with fingerprints, handprints and footprints for three years without any problem until now so I can't help thinking it's a kiln issue because whatever methods I've been using have worked until now. I was advised to sand the back of the cufflink before soldering to ensure that it's smooth enough although had read about burnishing and wondered if that would be better. Still I'm not sure that explains why a small amount of silver has chipped away when the cufflink post has come off. I know silver is a relatively soft metal but surely it shouldn't break like that?

CJ57
17-08-2015, 11:54 PM
As Carole has said few of us work with pmc so can't explain the chipping as it doesn't behave like sterling or fine silver. On the couple of occasions I have used it and had to solder onto it it has needed burnished to harden the surface rather than sanded or it swallows huge amounts of solder. If it hasn't happened before then you are right it's probably a kiln issue because no silver doesn't chip.

vsilvered
18-08-2015, 12:28 AM
I do work in silver metal clay and am able to produce consistent results with the things I make, which are mostly rings and earrings. Sadly, we don't get to see/hear about the many amazing jewellery artists out there with skills creating amazing/beautiful and long-lasting stuff with this medium (e.g. Gorden Uyehara, Liz Hall, Celie Fago, Lisa Barth, Holly Gage)

I'm sorry to hear about your current troubles with your cufflinks. As previous folks have said, it could possibly be that your kiln is not reaching a high enough temperature for sintering to occur. You don’t mention how long you fire your silver metal pieces for. If the firing time is too short (also known as ‘short-firing’) then problems can result in the final product. Work hardening your pieces afterwards with a hammer is also important - this is because when the metal comes out of the kiln, its fully annealed and therefore soft. The work hardening if done gently can be done safely without compromising any designs on the piece, before polishing.

For example, those firing schedules listed in the packets of PMC3, are only minimum times and temperatures. A full firing at 1650 deg F (around 900 deg C) for 2 hours results in a much stronger material.

A really useful guide to firing silver clay can be found on the cooltools.us website here (http://www.cooltools.us/category-s/1432.htm). It contains lots of information about why a full 1650 F/2 hr firing of silver clay is important.

It is possible to produce consistent results with silver metal clay and it certainly helps to understand the material that you’re dealing with and what is happening to it at a molecular level during firing. I always point folks in the direction of Kate McKinnon’s book ‘Sculptural Metal Clay Jewelry: Techniques and Explorations’. Kate McKinnon is a jewellery artist and scientist who when asked to test silver metal clay when it was first produced got together with her scientific chums to analyse this material under varying firing conditions and different processes to see what was going on with this material at a molecular level and to figure out what were the optimum firing conditions to produce a strong final product.


Hoping you find a solution to your current issues.

SteveLAO
18-08-2015, 08:32 AM
Might be worth your while having a chat with Lisa Cain at the mid Cornwall school of jewellery. apparently she is one of the foremost teachers of PMC. Here is a link to her: http://www.mcsj.co.uk/lisa-cain-tutor-profile.html
She is also director of the PMC guild so may well have come across this problem before?

orestruck
18-08-2015, 02:54 PM
I have been using metal clay for about ten years. What you are seeing is actually quite normal for fired silver clay. You need to remember that when fired, it doesn't liquefy, so it's molecular structure is not the same as, say, a cast piece or a piece of rolled sheet. Yes, the molecules "sinter" at the required temperature, but the structure is in essence porous, like microscopic honeycomb, if you will. Because of this, it will never be as strong or tough as rolled or cast metal. I have no doubt that my kiln is firing correctly, but I bet if a tried hard enough with pliers I could break off a piece of fired metal clay and it would look the same inside as you describe - slightly chalky.
It's one of the down sides to the medium, sadly.

Sarah

KJS
18-08-2015, 05:48 PM
Thank-you for your reply Caroline. I haven't used a burnishing tool before and when I looked online there seemed to be different types. Is there any type in particular you'd recommend for burnishing the back of a cufflink before soldering? Many thanks :)

KJS
18-08-2015, 05:56 PM
Thank-you V, Steve and Sarah for your very helpful replies. I will contact Lisa Cain as suggested to see if she has any insights. I think I'm beginning to understand that fired silver is not the same as cast and that extra measures are needed.
V, I've been firing at 750 degrees for 15 minutes although from what you said and the very helpful link you posted it seems I could go to a higher temperature for longer. I'm still mystified why it's been ok up until now though! I haven't used a hammer before although one did come with the package of equipment and materials that I originally bought when I started with silver clay, but there was no indication in the online course how to use it.

Many thanks :)

Melanie
18-08-2015, 09:14 PM
Whats with the silver clay bashing... Most of the issues complained about with silver clay are due to under-firing or bad technique, not really the fault of the material... it is certainly possible to produce consistent and good results using silver clay, but like anything you need to go through trial and error to learn what gives a good result. Anyway... agree that the issue here is most likely firing, 15 minutes seems very short, may well be what the pack tells you to do, but experience taught me to ignore the instructions and fire longer for stronger. We use sterling clay and our pieces are fired for about 4 hours. The downside with having one-off silver items cast is the timescales involved with sending to be cast, hallmarked, engraved etc. And castings can also fail, so unless you pay for a mould to be made of each unique piece, which will dent your profits quite some, then you will prob have to re-do the odd wax. In my experience most customers wanting a silver fingerprint charm would not want to wait 6-8 weeks, lots don't like waiting 3-4 weeks :)

ps_bond
19-08-2015, 06:08 AM
Whats with the silver clay bashing...

I've gone back through all the messages and I really don't see anything I'd regard as bashing. Silver clay is a porous, sintered product that is not as strong as solid metal; it requires more solder than solid (again due to the porous nature) and is a pig to repair by welding (due to the same issue). I've seen so many failures with it that I have to wonder how much is really down to bad technique - and if the instructions say to fire for a certain time, then it's not unreasonable to expect that to suffice.

For one-offs casting is a more expensive option - but that segues straight into my usual rant about pricing things properly. If I were doing them I'd probably go the route of casting the item, doing an image transfer and engraving the print; laser engraving (GETi, for example) would be another option; there's also the Gravograph machines that'll do images, but I'm not sure what level of detail they can do.

Now, if you want to see some real silver clay bashing I can do that quite easily; I don't use it and I can't see any need for it in what I do. :D

KJS
19-08-2015, 09:02 AM
Would those of you familiar with Art Clay Silver agree with firing at 1650 degrees Fahrenheit or 900 degrees Centigrade for two hours? This is such an increase in temperature and time from what I've been doing and what the instructions say but the consensus does seem to be to fire hotter and for longer. All advice gratefully received!

Melanie
19-08-2015, 09:28 AM
Sure, however lots of people do use silver clay and do need it for what they do, in particular it lends itself very well to the keepsake market and provides a good way in to learning more traditional jewellery skills to complement its use. I really don't want to stir a hornet's nest, have found this forum extremely helpful and supportive, but the suggestion that all items made from silver clay are not suitable for sale is one I just can't agree with it - but then I am not going to am I as my family are fed, clothed and sheltered solely on the sales of my silver clay jewellery ;)

I understand about the structure of clay v's solid metal and yes, if I twist and twist a piece of sterling silver sheet with pliers the same thickness as a piece of properly fired sterling clay, the sheet will last a fraction longer, but really, with that level of force both are quickly distorted. If a piece has been properly fired it will withstand normal treatment. Totally agree that the instructions given should give the best result, but they don't, and a quick google shows up alternative firing schedules and lots of research and experiments by silver clay artists problem solving and getting consistent and strong results from their firing schedule.

There are other ways of making similar jewellery, but they are expensive and not really accessible to a small home-run business. Gravograph machines were about £6k last time we enquired, and they don't produce the same result as the clay does with the impression. Same argument with laser engraving really, but add £20k or so if you want your own laser and don't want to outsource. You also need have everything else in place to ensure you can get the return from the investment, a lot of small businesses simply won't be in the position to make this happen.

Melanie
19-08-2015, 09:39 AM
Am not familiar with art clay silver but the best way to test is to sacrifice a small piece of clay as a test strip. Fire it like you said above then bend with pliers and see how far it goes before it breaks. I would compare it to a test strip fired using your old 15 minute firing program. Then you will have peace of mind as to the extra strength you are achieving using the new schedule and your kiln.

KJS
19-08-2015, 09:55 AM
Thank-you very much Melanie for your input. Out of interest why did you choose to use sterling clay? Is it considered superior to fine silver clay?

Melanie
19-08-2015, 10:08 AM
A few reasons really, I used fine silver clay for about six months before moving to sterling, mainly because it is stronger than fine silver, because customers are used to buying sterling silver whereas they are confused as to what fine silver is, and because the main competition had chosen to move to sterling. You should still work harden pieces. Mine all get a good post-firing thwack with a hammer as part of their flattening out process ;) The firing process is more demanding, it has to be fired once on an open shelf, and then fired again in carbon, but once you get to grips with that it is good to work with in both wet and dry stages, and polishes up beautifully.

KJS
19-08-2015, 11:37 AM
Thanks Melanie, that's interesting to know. I'd seen a major company using sterling and was impressed with the mirror finish but was put off by the complicated firing. Might give it a go though!
For now though is it fair to say then that I'd need to hammer, burnish and increase the time and temperature? I mean you couldn't get away with firing low and quick and then just burnishing before soldering? I will experiment but it's good to get expert opinions! Additionally I was wondering about shrinkage. I mean if firing the way I have been causes about 8 or 9 per cent shrinkage would firing much longer and stronger continue to shrink? Many thanks!

Melanie
19-08-2015, 11:53 AM
If you fire longer it will shrink more, and personally I would defo fire longer, work harden, and burnish the back before soldering. Firing at low temperatures for a short time isn't going to produce the strongest result I'm afraid.

KJS
19-08-2015, 12:03 PM
Thank-you I'll definitely increase the time and temperature then. At the risk of sounding like a complete amateur, what does work hardening involve? As I mentioned in a previous post I received a hammer as part of the silver clay starter package that I bought but there was no mention of what to do with it. Similarly I wasn't taught about burnishing and had only been sanding before soldering the backs onto the cufflinks. Is there a particular type of burnishing tool that would be best for this? Sorry for all the questions!

Melanie
19-08-2015, 12:24 PM
an agate burnisher like this will do the trick http://www.cooksongold.com/Jewellery-Tools/Agate-Burnisher-Knife-Shape-Blade-prcode-999-AOA3, To work harden, use a raw hide hammer and a steel bench block and well, hammer :) Will also flatten the piece for you as quite often charms warp in the kiln. Some peeps swear tumbling work hardens pieces, but am not convinced, lots say it doesn't...

KJS
19-08-2015, 04:57 PM
Thank-you so much for this Melanie :) Yes I'd noticed that particularly square cufflinks warp which I don't think helped when it came to soldering the backs on! As you mentioned tumbling, can I ask is this something you'd recommend for polishing? I was taught to use the three grades of sanding sponges before and after firing but have read about other methods including tumbling although wasn't sure if this might affect things like fingerprints?

orestruck
20-08-2015, 04:20 PM
Just a thought.....the pieces you have had problems with, are they fresh clay from the lump or rehydrated in any way? Also, how much oil or slik are you using with the clay, have you changed this at all recently? If you imagine, you could get a pocket of grease inside a fold in the clay before firing....sort of like puff pastry if you get my drift!
Just a couple of extra things to think about.....

Sarah

KJS
20-08-2015, 06:34 PM
Hi Sarah, yes they have been fresh clay not rehydrated. I'm not sure what you mean by oil or slik (I'm beginning to realize there's an awful lot I don't know about silver clay!) but I have been using quite a bit of badger balm on my fingertips if that could have the same effect? Possibly more than before because of the clay drying out quickly in the warm weather.

medusa
20-08-2015, 07:14 PM
I still get the odd order for PMC (I use PMC3+) and from playing around with it in the past I've found soldering to be almost impossible. There is a reason they sell those embeddable findings for PMC which is that it solders erratically. I find it works best when it is just 'as is', either as beads or pendants.

KJS
20-08-2015, 09:59 PM
I agree that charms and pendants are alot less trouble than soldered pieces! Am not familiar with embeddable findings though. Is this something that could be used for cufflinks do you know?

enigma
21-08-2015, 12:58 PM
Ive never really done much with silver clay but Medusas post just reminded me I saw the embeddable findings here ages ago and they have cufflinks:
http://www.metalclay.co.uk/cufflinks/

KJS
21-08-2015, 01:56 PM
Thank-you very much for that Enigma :) They look alot easier than soldering. The only downside is the cost although with the amount of cufflinks I've had to replace it would probably be worth it!

Patstone
22-08-2015, 06:14 AM
Is all silver clay (or silver in a plastercine type) porous. A friend of mine has just started to do it and she said PMC used to be porous but the modern stuff isnt now. To me that just sounds rubbish, but thats what she has been taught. Next month she is learning how to do bezels, cant imagine them successfully holding a stone for long. She is being taught by a proper teacher, not just picking it up herself.

vsilvered
22-08-2015, 07:48 AM
Is all silver clay (or silver in a plastercine type) porous. A friend of mine has just started to do it and she said PMC used to be porous but the modern stuff isnt now. To me that just sounds rubbish, but thats what she has been taught. Next month she is learning how to do bezels, cant imagine them successfully holding a stone for long. She is being taught by a proper teacher, not just picking it up herself.

Hi Patstone,

If silver metal clay is fired at 1650 def F for 2 hours minimum and the fine silver object work hardened afterwards (as one would do after annealing any metal in order to strengthen it), then the resulting fine silver object is strong and sturdy.

In her first book ‘Sculptural Metal Clay’ (sadly out of print), Kate McKinnon, who is a jewellery artist and scientist, explains that the process of firing metal clay is to get the small particles of metal to stick together and the closer the kiln can get to the fusing temperature of fine silver (approx 1750 F), the better the strength of the pieces will be. Firing at 1650 deg F for 2 hours brings the material as close to its fusing temperature and strengthens pieces structurally because the boundaries of the metal grains merge together - work hardening the resulting metal afterwards, further strengthens the metal. Underfiring silver metal clay for shorter periods of time and not work hardening the work afterwards can result in porous and fragile pieces prone to breakage.
Kate's results have come after her own extensive tests of the material under laboratory conditions as well as consulting chemisty and metallurgy professors at Brown University in the U.S.

I’ve fired my silver metal clay pieces (both Art Clay and PMC3) this way for years, making rings, earrings and clasps, having them successfully hallmarked and have seen no issues in terms of durabiltiy/strength.

The clasp on the bracelet is fine silver and the following image shows the hallmark on the back.

80418042804380448045


With regards to bezel settings, check out Lisa Barth’s work here in metal clay:

https://uk.pinterest.com/dreamfaire/metal-clay-dreams-of-lisa-barth/

If the fine silver bezel is formed, embedded into the wet clay and then fired when bone-dry, the bezel fuses to the support that it has been embedded creating a very strong bond.

Hope some of this answer helps :)

medusa
23-08-2015, 07:39 PM
I think the biggest problem with the old style PMC was that as fine silver it wears too fast, especially for everyday wear which is what most people want with the fingerprint jewellery. I'm guessing that the newer sterling PMC gets around this issue but whilst I really like PMC when it's been used creatively, it just doesn't float my boat any more as a material to work with. I guess I just like cutting and hitting stuff now!

vsilvered
23-08-2015, 08:54 PM
Hi Medusa,

By it's nature fine silver whether its derived from PMC/Art Clay or traditional sheet metal or wire, will always be softer than Sterling silver as it doesn't contain the copper... which is what makes Sterling silver more durable.

All those items pictured in my previous post were made from PMC over 5 years ago.. I wear them regularly and because of their thickness and the bigger and bolder textures that I use, they wear very well. :)

For me with PMC, the key thing is understanding the material I'm working with, i.e. understanding its limitations and then designing/creating work to take those limitations into account as well as take advantage of its creative possibilities.

There are jewellery artists working out there using PMC/Art Clay creating, durable pieces of wearable art of jaw-dropping intricacy and beauty (some I've mentioned above in a previous post) that go beyond fingerprint jewellery, like Anna Mazoń (http://drakonaria.com (http://drakonaria.com/)) - it's shame we don't get to see more of this type of wearable art featured.

(No offence to those who make fingerprint jewellery, which provides great joy to people who create it and those who receive it)

enigma
23-08-2015, 10:01 PM
Some beautiful pieces there, thanks for sharing the links :)

Sandra
01-10-2015, 12:26 PM
T



There are jewellery artists working out there using PMC/Art Clay creating, durable pieces of wearable art of jaw-dropping intricacy and beauty (some I've mentioned above in a previous post) that go beyond fingerprint jewellery, like Anna Mazoń (http://drakonaria.com (http://drakonaria.com/)) - it's shame we don't get to see more of this type of wearable art featured.

(No offence to those who make fingerprint jewellery, which provides great joy to people who create it and those who receive it)

Coincidentally my first experience with PMC was when I booked a weekend course with Anna Mazoń in Belgium. I did it just for fun - but actually the course gave me a new appreciation for metal clay. I know it seems perhaps PMC is frowned upon by some, but there are some beautiful and amazing pieces of jewellery being created this way.

Dennis
01-10-2015, 04:55 PM
there are some beautiful and amazing pieces of jewellery being created this way.

I don't think that was ever in doubt Sandra. It's just that the process doesn't turn me on and I guess there are others like me. Dennis.