Re my original message of the Disapearing Diamond.
Linda-Kaye, you have saved my soul. Don’t be afraid of admitting the
PMC Instructor thing, you are the best! I was almost to admit the
possibility of the stone not being a Diamond, but will retract that
thought.
My own experience - did fire two real blue sapphires - one came out
blue the other green - no comment wanted; and the pink tourmaline
stayed pink!
Cheers
Rose Marie Christison
Hi Linda,
I posted several weeks ago in response to this thread that a similar
thing used to happen to me when I started casting with diamonds and
sapphires (corundum) many years ago.
Often times the stones would disappear. I had failed to support them
with adequate “fingers” of investment and they would fall into the
mold cavity, lost with in the casting.
I understand that the PMC remains in place during firing–no mold
cavity – but could a similar process be taking place?
Take care,
Andy
Hi, Linda Kaye-Moses,
Your list is most interesting. http://tinyurl.com/you9s9
I am certainly going to heat up garnets, moonstone and preridot to
about 600C for 30 minutes( and longer) and see if they survive.I
won’t heat up tourmaline, because in a previous post (sorry, I can’t
give you the url, because I could not find it on the ganoksin search
engine) I heated tourmaline to (I think) some 700C before it died. I
do think that my “experiments” are not the true blue of everything.
It might well be that diamonds DO evaporate in an situation like PMC
Standard. I do not work with PMC, but it would be interesting if
there was a PMC worker on ganoksin that put a diamond in the oven
properly and photograph the results.It is hardly difficult or
expensive and the result would be most interesting for all.
Rest assured, the garnet, moonstone, periodot results are just over
the horizon! Coming to a computer near you!
Cheers, Hans Meevis
http://www.meevis.com
I understand that the PMC remains in place during firing--no mold cavity -- but could a similar process be taking place?
No, it has been well established, since at least 2002, that diamonds
burn away to nothing at 1650 for two hours.
Elaine
http://www.CreativeTextureTools.com ™
Hard to Find Tools for Metal Clay
I have already heated these stones many times to 1200 F. without any
harm. Kevin Whitmore of Rio Grande, and Aida Chemical Industries have
already done this research and each has posted results of stones
heated to 1600 F. and 1200 F. We have been using these guidelines to
fire gemstones in metal clay for several years now.
Jackie Truty
Art Clay World, USA, Inc
It might well be that diamonds DO evaporate in an situation like PMC Standard. I do not work with PMC, but it would be interesting if there was a PMC worker on ganoksin that put a diamond in the oven properly and photograph the results.
It occurs to me that if the mechanism is evaporation by oxidation,
the experiment could just as well be done with diamond powder, about
$1.00/ct. Fire some in a crucible and weigh the crucible before and
after.
Al Balmer
Sun City, AZ
It occurs to me that if the mechanism is evaporation by oxidation, the experiment could just as well be done with diamond powder, about $1.00/ct. Fire some in a crucible and weigh the crucible before and after.
I don’t think this would work as it does not take the binder into
account. The binder burns away during firing, so you would need to
know the weight of the binder as well as the weight of the diamond
powder.
Pat Waddington
www.pajed.co.uk
Kevin Whitmore of Rio Grande, and Aida Chemical Industries have already done this research and each has posted results of stones heated to 1600 F. and 1200 F. We have been using these guidelines to fire gemstones in metal clay for several years now.
Without wanting to flog a dead diamond to death, but could Ms. Luther
or Ms.Truty possibly direct me to some literature on this subject? I
have an intense interest in the heating of stones in general.
Thanks, Hans
I am certainly going to heat up garnets, moonstone and preridot to about 600C for 30 minutes (and longer) and see if they survive....
Hmmm. Many, many people have been doing this for some years now.
There are several published lists (from reliable sources) indicating
what result you can expect when heating these stones using metal clay
firing schedules. Now, if you were to say you wanted to do it so you
could take and publish before and after microscopic images of the
stones or give a detailed description of the stones before and after
using magnification, that would be a great thing. But merely to try
it and “see if they survive” would be redundant and not advance
knowledge.
...but it would be interesting if there was a PMC worker on ganoksin that put a diamond in the oven properly and photograph the results.
I think the term “properly” is the key here–you need to define what
you mean. You obviously have certain expectations of what is “proper”
and don’t feel that the reported results were achieved in a “proper”
manner. Do you mean a well defined scientific experimental process?
Although not accompanied by images, the results reported by Kevin
Whitmore, Art Clay World, myself, and others have been achieved by
what most people would consider acceptable experimental procedures.
Not perfect, but good preliminary results. Generally what is lacking
is the easily found posting on the web of the detailed methodologies
used to arrive at the reported results. Procedures have been
presented and discussed at conferences, on the PMC Guild discussion
board, and the yahoo metalclay list.
A more detailed look at the various stones including test firing
using numerous stones from different sources is what is really
needed next along with published results and methodology.
Garnet is an excellent example of where we need more and
systematic testing. Many types of garnet seem to do ok when fired at
metal clay schedules, though rhodolite tends to darken. As more and
more people have been experimenting with firing garnets in place,
there have been reports of trouble–mostly with rhodolite. The
problem is that it sometimes takes on a dark metallic (think
polished hematite) surface sheen after firing. The current best
hypothesis is that the sheen may be a product of heating/cooling the
iron in pyrope-almandine series garnets or that it is caused by iron
in (cork clay) armatures sometimes used in making hollow pieces. I
would love it if a gem expert would take on this question and figure
out what is going on and why…
Mary Ellin D’Agostino, PhD
www.medacreations.com
I don't think this would work as it does not take the binder into account. The binder burns away during firing, so you would need to know the weight of the binder as well as the weight of the diamond powder.
Binder? The diamond powder I use is just diamond. Are you thinking
of polishing paste, or diamond tooling?
Al Balmer
Sun City, AZ
Sure, you can find Kevin Whitmore’s results at
http://tinyurl.com/you9s9 there’s a section with technical papers,
etc.
or at the 2002 Conference papers section
http://www.PMCConference.com
The forums at the PMC Guild.com site will also have more personal
experiences of folks who have done it.
Elaine
http://www.CreativeTextureTools.com ™
Hard to Find Tools for Metal Clay
Hi Hans,
Sorry I am late to this discussion. The Gemological Institute of
America states in their Gem Reference Guide:
Diamond, Stability, Reaction to Heat: begins to vaporize in an
oxygen-rich atmosphere at 690 C to 875 C.
I was told by a customer in 2001 or 2002 that they had an experience
where their diamonds had been completely vaporized while firing
their original-formula silver PMC for 2 hours at 900C. I wrote a
small article warning PMC artists about this danger of firing
diamonds for Studio PMC, (the PMC Guild’s magazine at the time).
I have since successfully co-fired small natural diamonds in newer
formulas of PMC for 30 minutes at 600C. Despite my success, I
generally don’t advocate the insertion of diamonds in PMC. I worry
that people will forget, and fire their PMC over the 600C mark.
I have never intentionally vaporized a diamond, and don’t really see
the need. The GIA and other reputable sources report that diamond
will vaporize given access to enough oxygen and temperature. Any
research I have shared with the metalclay community has been to give
greater access to gemstones that have a decent chance of a successful
trip to the kiln.
Kevin Whitmore
Rio Grande
I mentioned reports on preliminary work–basic tests on whether
stones survive or are obviously damaged when heated at metal clay
firing schedules. To my knowledge, no one has reported on systematic
testing on multiple stones of the same type from different sources.
Repeated testing is a great thing, but we are at the stage where we
need more in-depth formalized testing and reporting with expert
analysis of the results. Most of the reported testing is very basic
has been done by amateurs (like myself), so I am sure that far better
methods and analysis can be provided by an expert in gemology,
geology, or chemistry.
The best formal report has been made by Kevin Whitmore of Rio Grande.
He has reported on the Rio Grande tests at the PMC Guild Conferneces
at least twice. I believe you may find notes on it at
www.pmc-conference.com in the techinical info and notes sections for
past conferences. For more you would have to contact
him.
http://tinyurl.com/32cuyl
http://tinyurl.com/2lmldm
Derik Metzger has done a lot of testing and reported his results in
a self published book. I do not have current contact info for him,
but you can probably find him through the PMC Guild bulletin board.
For more formal results from Aida Corporation, you should contact
Jacke Truty at Artclay World:
Mary Ellin D’Agostino, PhD
www.medacreations.com
Maybe I am coming too late to this discussion but here is my two
cents. I was told by my PMC instructor that certain stones can NEVER
be fired in PMC. Diamonds, being composed of carbon, are one of
those stones. The bottom line is this: don’t heat anything up you
cannot afford to lose. I’ve used synthetic spinels and CZs, sapphires
(they usually get darken) and that’s about it.
Ellen Lyons
http://www.ellenlyons.com
Binder? The diamond powder I use is just diamond. Are you thinking of polishing paste, or diamond tooling?
The binder referred to is that in the metal clay.
Pat Waddington
The binder referred to is that in the metal clay.
There seems to be a bit of a mix up here. When I read the post which
suggested trying diamond powder, I assumed that the person meant
heating the diamond powder on its own but under the same conditions
as one would heat the original PMC, just to see whether or not there
was any diamond matter left at the end of it.
Helen
UK
Binder? The diamond powder I use is just diamond. Are you thinking of polishing paste, or diamond tooling?
Al, the binder that is referred to above is the binder of the metal
clay. PMC and ACS products are 99.9% refined silver in a flexible
binder that allows the metal to be hand shaped and molded, then
fired. When it is fired, the binder burns away leaving fine silver.
BBR - Sandi Graves
Stormcloud Trading (Beadstorm)
651-645-0343
St Paul, Minnesota
Reading all the posts on the subject of the disappearing Diamonds, I
am forced to wonder if it is not necessarily only the temperature and
presence of available Oxygen that is causing diamonds to disappear?
One has to take into account the binder material itself in the PMC,
as it is converted into a gaseous state and what it’s chain of
chemical reactions are? It may be directly reacting with the carbon,
or may only be acting as a catalyst.
This could easily account for the differing results that Hans has
had, as well as the differing results depending on the temperature
that PMC is fired at as the decomposition products of the binder may
well be temperature dependant…
Just my 2 cents of fog to this discussion…
Kay
There seems to be a bit of a mix up here. When I read the post which suggested trying diamond powder, I assumed that the person meant heating the diamond powder on its own but under the same conditions as one would heat the original PMC, just to see whether or not there was any diamond matter left at the end of it.
You are exactly right. The question is the effect on the diamond,
not the clay.
Al Balmer
Sun City, AZ
I finally got my ‘original’ silver PMC. I made a model and fired it
at 900C for two hours. The diamonds were burnt just like if you
over-heat them with a torch.but they were still in the silver. I put
up some pictures on my blog. Check out http://tinyurl.com/2j8hwf
As I say in my blog, I doubt very much that even small diamonds will
evaporate in 2 hours at 900C.
Cheers,
Hans.
http://www.meevis.com