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Metal clay jewelry disclosure


#1

I have been getting some conflicting regarding metal clay
jewelry. I have been using metal clay PMC3, mostly for rings and
intend to complete PMC certification 1 at the end of this month. I
am also taking traditional metalworking classes and my teacher says
that fine silver is not jewelry quality. She also indicates that it
is porous and weak. I have been selling my work and I don’t want to
mislead my customers who I always inform that I am using fine
silver, and my experience has been quite good. I realize that fine
silver is not as strong (about 1/2 as strong according to the PMC
guild) as sterling but does that mean I shouldn’t use it for jewelry
especially for rings. I would also like to cast with my fine silver
scraps but she feels the resulting product would be to weak to use. I
also use the technical on firing schedules to acheive the
strongest rings and alway work harden in a tumbler. Can anyone give
me some clarity on this and the limitations of PMC in jewelry
making. I have been wearing rings that I have made daily with no
evident problems. Thanks ahead of time for your comments.

Cindy


#2

Hi,

This is a valuable discussion that is ongoing and has been addressed
many times, though it doesn’t hurt to keep it going.

Your instructor is only partially correct (and therefore, partially
incorrect). Sterling Silver alloys were created to produce a durable
metal. Fine silver from metal clay is less dense than Fine Silver
that has been milled (sheet/wire/etc.). Fine Silver that has been
milled is only slightly less durable than milled Sterling Silver.
Fine Silver from metal clay is about as porous as cast Fine Silver,
but, in contrast, the porosity in the metal from metal clay is even
and very fine. The conclusion one might draw from this, is that
fully sintered Fine Silver from metal clay is a modicum less durable
than milled Sterling Silver and that, compared to cast metal, it is
a little bit stronger. That is all correct.

I generally don’t recommend ring making from metal clay to my
students. However, there is an exception, in my opinion. A ring
shank (and for that matter, a cuff bracelet) that is of sufficient
thickness, would be durable and strong enough for that purpose. So,
when I’ve made rings, I always make them thicker than I would make a
comparable design from milled sheet or wire.

There are two steps that I consider essential. The first is to
always fire metal clay in a kiln. I know that there are metal clay
users who swear by torch-firing, but I do not think that this
produces a strong product. The second critical step in firing Fine
Silver metal clay to create a stronger product, is to fire at the
highest temperature for the longest duration (1650 degrees F for two
hours), disregarding the manufacturers’ low temp/short firing
schedules. This produces the strongest post-fired metal. The
critical finishing step for ALL fired metal clay is tumbling with
steel shot. This will surface burnish/compress and create a somewhat
more durable jewel.

Now, all of that being said, it is likely that wearing a ring made
from metal clay will produce wear, surface-burnishing or
’-compression’ (my term) where the ring is stressed, usually on the
sides and palm side of the shank, sooner than those areas would show
wear in milled Sterling or Fine Silver. The bezel area does not seem
to be as prone to this.

Fine Silver metal clay is excellent for any number applications and
is good for ring making, though not excellent. You are fortunate
that you have other jewelry making skills that you can use in
conjunction with your metal clay skills (and your soon to be
acquired certification). Fine silver makes for a very beautiful
jewelry object and should not be discarded as a material for this
purpose, as long as the limits of the material are taken into
consideration, AS WITH ANY MATERIAL USED FOR JEWELRY MAKING.

Note: I’ve found that many who have been schooled in traditional
jewelry making techniques are skeptical of the use of this
relatively new kid on the block, metal clay, even though it’s now
been available for almost fourteen years in the US and is now being
used internationally as well. If your instructor has not already
taken a class in the use of metal clay, you might step up and
encourage her to do so (or demonstrate the wonders of metal clay to
her). This ‘tool’, metal clay, is a useful and intriguing adventure
in object-making and has formed an integral part of the repertoire
of that I use to make my work (been working as a jeweler
since 1978; using and teaching the use of metal clay since 1996).

Hope this is helpful,
Linda Kaye-Moses


#3

Hi Linda,

This is a valuable discussion that is ongoing and has been
addressed many times, though it doesn't hurt to keep it going. 

One of the reasons is that there is still a lot of misinformation
that is put out on the topic.

Fine Silver that has been milled is only slightly less durable than
milled Sterling Silver. 

This is not correct, the wear resistance of fine silver is poor.
This is why copper is added to silver to harden it to increase its
durability. Fine silver has a hardness of 27 HV when annealed,
sterling silver is 63 HV as annealed. Fine silver has a tensile
strength of 125 MPa annealed and sterling’s is 276 MPa. Sterling is
roughly twice as hard and twice as strong as fine silver.

If you go to the PMC guild website and download this chart

http://pmcguild.com/download/Tech_Data/Tensile_Strength_Comparisons.pdf

you will see that the strongest PNMC is 10% weaker than fine silver.
The numbers on that chart for wrought and sterling silver roughly
correspond to other published data for annealed material. This chart

http://www.pmcguild.com/download/Tech_Data/Comparison_of_PMCs.pdf

lists shows hardness data and shrinkage data for various firing
times. I would like for someone to explain how they got hardness
numbers greater than wrought fine silver though, not that I don’t
believe it I would just like to know what the mechanism is for the
greater hardness measurement. Typically with greater hardness you
would expect to see higher tensile strength but the data is not
showing that.

Fine Silver from metal clay is about as porous as cast Fine
Silver, but, in contrast, the porosity in the metal from metal clay
is even and very fine. 

theoretical density of fine silver is 10.49 gm/cc the above chart
lists the greatest density for PMC3 as 9.9 or 94.3% of fine silver.
If your caster is giving you castings that are less than 88% dense I
would change casters. Yes the porosity is evenly distributed but
what difference does this make to the end user?

The conclusion one might draw from this, is that fully sintered
Fine Silver from metal clay is a modicum less durable than milled
Sterling Silver and that, compared to cast metal, it is a little
bit stronger. That is all correct. 

One might, but this would be an incorrect set of conclusions based
on the PMC Guilds own published data.

Regards,
Jim
James Binnion
James Binnion Metal Arts


#4
lists shows hardness data and shrinkage data for various firing
times. I would like for someone to explain how they got hardness
numbers greater than wrought fine silver though, not that I don't
believe it I would just like to know what the mechanism is for the
greater hardness measurement. Typically with greater hardness you
would expect to see higher tensile strength but the data is not
showing that. 

James,

I know very little about PMC, but I do know that there is some type
of binder included. If some carbide is produced during the sintering
process that will account for the increased hardness with
simultaneous reduction of tensile strength. Carbide can be produced
anytime carbon is present during elevated temperatures, but I don’t
know what carbide can be produced at these lower temperatures used
for PMC. Just spit-balling.

Dan Culver


#5

Aside from the technical aspects of the strength of the various
metals I have another concern.

You are letting your customers know that it is metal clay. Which is
great and as it should be. But do all?

I recently saw a show prospectus that said all metal clay items
needed to be labeled as such. I agree.

If a unwary customer buys a ring out of “silver” and if doesn’t wear
as previous silver rings wear they wonder. And often that wonder
turns to doubt which can extend to other jewelers who are selling
sterling rings.

In the case of metal clay jewelry I think it needs to be disclosed
at point of sale & also marked on each piece. When I see a jeweler
selling metal clay pieces as fine silver and not telling their
customers that it is metal clay I wonder why they are hiding that?
Its not good for our business to confuse customers.

Carla
http://carlamfox.com


#6

Linda,

I’ve taken only one class in silver clay use and don’t consider
myself an expert on it at all. During the class I made three pendants
and one charm but have thought about making rings with the clay. I’d
love to hear what type of projects you think silver clay is best used
for. Thanks.

Mara Nesbitt-Aldrich


#7
If your caster is giving you castings that are less than 88% dense 

That should be 98% not 88%

Sorry about that.

Jim

James Binnion
James Binnion Metal Arts


#8

OK Jim,
Thanks for the tech info. Much appreciated.

In spite of what the charts disclose, as described in your letter, I
would still consider metal clay rings, when, and only when, the
shanks are of sufficient thickness. As I have mentioned, both in my
letter and earlier, there are better methods for producing a ring
shank of more durability.

Metal clay is a door opening for many who have not had the
opportunity to learn other metal working methods. Some choose not to
explore further, but…it’s just an open doorway…one doesn’t have
to walk through it. However, it does encourage, and I mean that in a
literal sense (en…courage), many to enter the world of
traditional jewelry making methods.

OK, this voice will stop…now,
Linda Kaye-Moses


#9

Thank you both for your responses. They are very helpful.I have
studied the PMC Guild tables which are amazingly helpful. I do not
yet have a kiln and usually stovetop fire with lots of sucess…I rent
a kiln in order to get the maximum strength by firing at 1650 for 2
hours for certain rings. I love making rings with PMC but I think I
will have to do a bit more disclosure.

I will recommend a PMC class to my teacher, She is very creative and
I think she would really love it.

Thanks again,
Cindy


#10
I know very little about PMC, but I do know that there is some
type of binder included. If some carbide is produced during the
sintering process that will account for the increased hardness with
simultaneous reduction of tensile strength. Carbide can be
produced anytime carbon is present during elevated temperatures,
but I don't know what carbide can be produced at these lower
temperatures used for PMC. Just spit-balling. 

Carbides are metal carbon alloys, silver does not form them. I think
it may be a calibration issue but again I don’t know for certain.
Regards,

Jim

James Binnion
James Binnion Metal Arts


#11

Happy monday everyone- Is there such a thing? I’ve read most of the
forum about metal clay- But I have a question to add-is metal clay
(14k and sterling) as good as solid stock such as sheet, wire,
tubing and casting grain? My experience has always been with hand
fabrication. I have not moved on to metal clay because I’ve always
viewed it as you would a boxed cake mix vs. from scratch. Most
people I know would rather have the homemade cake. Is metal clay the
same quality as solid stock? I’m sure both have their uses, but I’m
hesitant to use metal clay as an alternate source.

Sincerely Jeane E


#12

Hello Mara,

Just one thought first before I answer your inquiry. Objects made
using metal clay are not metal clay once they are fired. That is a
somewhat obvious distinction, but an important, and sometimes
overlooked, one. Those objects are metal, sintered and solid.

If show promoters also require all jewelers and other metal artisans
to disclose “methods”, (like casting, fabrication, acid-etching,
die-forming, etc.) then it’s appropriate to list metal clay as a
method, not a final product. It is sufficient to disclose to a
potential customer or collector, that the item under consideration
is Fine Silver (or 22k Gold or bronze or copper).

The method of production may also be discussed, but it is important
never to be secretive or to hide about the jewelry being
considered. Describing the jewelry by defining its metal is not
deceptive. Deception occurs when about the ‘care and
feeding’ of the jewel is withheld,( i.e. how to wear, care and
polish and why),. This would normally include an explanation of how
the piece was made. At least that would be true for my approach to
selling my work.

OK. Mara…you ask which jewelry objects I consider most appropriate
for metal clay use (please understand that this is my opinion and
that other metal clay artisans may have different thoughts on this
issue): buttons, earrings, pendants, neckpieces, charms and charm
bracelets, cufflinks (with sterling findings). With some caveats
and/or adjustments for added strength: clasps, rings, bangle
bracelets and chains. I would not find metal clay useful for belt
findings, although the bronze clays may put the lie to that (I’ve no
experience with the base metal clays so cannot speak to this
application).

I hope that you find this helpful and certainly welcome
further questions. You can contact me off list, if you wish.

Linda Kaye-Moses


#13

For the moment, metal clay only comes in fine silver, 22 or 24k
gold, copper and bronze (there are new clays out there in steel and
others, but I haven’t tried them). “Good” is a relative term. The
metal clays are more porous than cast, don’t quite have the strength,
but for 99% of the time, they are strong enough for the jewelry for
which they’re made. I’ve been using Art Clay Silver for 10 years,
have made hundreds of pieces, including rings that I’ve been wearing
for years, and the pieces, when constructed appropriately, have worn
very well. I believe metal clay has its use, as a sculptural form, as
a time-saving adjunct to what is already out there. I’m taking
traditional metal smithing classes to be able to use both. Metal Clay
is well worth the time looking into it, IMHO.

Jackie


#14

Linda:

Customers are accustomed to fabricated or cast jewelry. Metal clay
jewelry mimics these age old methods. If it is not fired correctly
what looks like metal can crumble into unfired clay. Also metal clay
doesn’t have the strength or durability of milled metal.

If I use 14k instead of 18k gold I mark it. My question, why "hide"
the fact that it is metal clay? It seems like metal clay enthusiasts
are trying to fool the customers as to material and technique.

Carla


#15
If I use 14k instead of 18k gold I mark it. My question, why
"hide" the fact that it is metal clay? 

For the simple reason that, by the time it reaches the customer, it
IS NOT metal clay, it is fine silver. 14k is always 14k, but metal
clay is only metal clay until it is fired, so the comparison is not
apt.

Personally, I don’t mark it one way or the other, and I explain the
method to customers. Knowing a story about the making of a piece, as
discussed before on this forum, raises the customer’s interest level.

As for the “need to know” because it might not be durable enough,
the solution is not to sell anything shoddy, underfired, or poorly
constructed, regardless of material. Duh.

Noel


#16

I fabricate and do not cast. I watch two Art Clay Masters work every
day and marvel at the things that they can do with their scuptural
skills that are impossible for me.

If a metal clay piece is badly made, the fault is the artist’s, not
the medium. If I make a piece with a cold solder joint that fails,
the fault is not the milled metal or the solder.

The mark for silver metal clay is “.999 fine”. There is no mark for
"inexperienced/incompetent artist".


#17

Hi Jackie,

No need for any humility, Jackie (you did said, “IMHO”) here. Jackie,
you have established your reputation in the metal clay field. You
know what you’re talking about. Great to hear that you are exploring
other methods and techniques for creating metal objets. One can never
have too many ways to make one’s work.

Carla spoke of fine silver jewels made using metal clay that
crumbled and fell apart? What metal clay artisan would dare to show
or sell work that would crumble, do you think? How many jewelers
using other techniques would do so? As you, Jackie, and I know,
properly fired (sintered) metal clay objets do NOT crumble…they
are fully fused metal objets, incapable of crumbling and, though,
perhaps not as dense as milled sheet, equally durable when used
appropriately. The critical phrases here are “properly fired” and
"used appropriately".

The objection that there is some form of deception being foisted
upon an unsuspecting public is inaccurate enough to be laughable.
It’s time to get over it folks…properly made objets made from
metal clay are durable enough to be worn for generations and THERE
IS NO REASON FOR (as if there ever is) ANY DECEIPT. Whatever the
metal is, the metal is,…fine silver, 22k gold, bronze,
copper…no deception there that I’m aware of. I always define (and
stamp) the quality of the metals I use, including fine silver
whether it is from metal clay or milled sheet. My collectors are
informed collectors, (by my choice) and I would hazard a guess that
all those who are using metal clay are equally informative when they
show their work. There is no attempt being made to fool anyone. Fine
silver is fine silver is fine silver…period.

I have been so fortunate to have been able to add metal clay use to
my jewelry making vocabulary for these past fourteen years. Do you
recall the first moment when you touched a saw to metal sheet, slid
it down and watched the metal dust come off the sawn slot? Do you
remember the sound of it? I do. It won my creative heart from the
start. And that’s how I felt about metal clay the first time I used
it. I invite those of you who love making metal jewels, who are
curious about metal clay, or who are confused by the myths about it,
to come take a class with an experienced metal clay instructor.
Jackie teaches. I teach. There are hundreds of excellent metal clay
classes at all skill levels being taught all over the world and a
great many wonderful metal clay books that teach its use. Come to
the PMC Conference in July. What’s the problem! Jump in…the
water’s fine.

Nuf said,
Linda Kaye-Moses


#18

I am a traditional silversmith that later learned metal clay. Once
metal clay is fired it is fine silver. If it is appropriate to use
fine silver in a piece of jewelry, it is appropriate to use metal
clay. I’ve never had a piece made from metal clay crumble, but I
have had a solder that I made on sterling silver not hold and fall
apart. You need to compare properly made pieces from both mediums,
not improperly made pieces.

Jane


#19
For the simple reason that, by the time it reaches the customer,
it IS NOT metal clay, it is fine silver. 14k is always 14k, but
metal clay is only metal clay until it is fired, so the comparison
is not apt. 

I couldn’t say it any better. 14k is always 14k, metal clay is not
always metal. It starts as clay & once metal, is not as strong as
fine silver. Customers need to be told. Let them make the decision as
to whether it fits their criteria for durability.

The question I am not getting answered, why the secrecy? If metal
clay people feel their material is just as good as fine silver and
other milled metal products, why keep it a secret?

Carla


#20

This has been a very interesting thread.

About 5 - 6 years ago, I made a pinky ring from Standard PMC. The
ring’s thickness is about that of a nickel. I have worn it a lot and
have never had a problem - it has never warped or dented. It is flat
with a design stamped in it so the thickness varies a bit.

Sandra in Snohomish
www.JulyCreek.com