Tig Dupre on thu 26 may 05
Dear Mudbuds,
I accidentally created a glaze I really like, and I'd like to find out
how to create it by design.
In the glaze studio, I kept buckets of all the old glaze tests I have
done, chucking the "bitters" of old tests into the bucket. When the
buckets filled to about the four gallon mark, I stirred it all up and
glazed some test pots with it. The glaze came out of ^6 a beautiful,
semi-transparent, deep-green, with speckles in it, probably from the
ash I used in several test glazes.
There are about six gallons of this glaze left. I'd like to have it
analyzed to see if I can recreate it from known materials. Can someone
recommend a lab in the USA I could send a sample of the glaze to? And could you
give me an approximation of how much it would cost? Also, would it
help if I told the lab what I remember of the materials that went into
the various glazes?
Thanks in advance for your help,
Tig Dupre
in Port Orchard, Washington, USA
URL Krueger on thu 26 may 05
On Thursday 26 May 2005 09:18 pm, Tig Dupre wrote:
> I accidentally created a glaze I really like, and I'd
> like to find out how to create it by design.
Tig,
Haven't we all done that ?
A question you need to ask before you spend money on an
analysis is what kind of analysis do you want. Are you
looking for SiO2 xx%, CaO xx%, etc or are you looking for
feldspar xx%, frit xx% ? If you want the former you need
someone who does chemical analysis; if the latter then it
would be a mineral analysis. I would guess that labs may
be capable of one or the other but maybe not both.
But, I'm sure you already know all of this.
Hey, I know who could do this for you. Send a sample to
Hollywood. The folks on CSI shouldn't have any problem
with something as simple as this. Or ??? Since you have
military contacts maybe you could convince someone that
this is of vital National Security and get the analysis
done at tax-payers expense. :-)
--
Earl K...
Bothell WA, USA
Gail Dapogny on fri 27 may 05
In our guild, each week we scrape down the back and sides of the spray
booth. and collect the scrapings in a bowl, free to anyone who wants
it. Many use it for the insides of pots where the outside is more
important than the inside. We have done this for...decades. It
comes out pretty much exactly as Paul has described, sort of a celadon
but deeper.
interesting, huh?
Gail
Gail Dapogny
Ann Arbor, Michigan
http://www.pottersguild.net/
On May 27, 2005, at 6:27 PM, Paul Lewing wrote:
> on 5/26/05 9:18 PM, Tig Dupre at marcy.dupre@US.ARMY.MIL wrote:
>
>> The glaze came out of ^6 a beautiful,
>> semi-transparent, deep-green, with speckles in it, probably from the
>> ash I used in several test glazes.
>
> Tig, I create and use a lot of scrap glaze in my process. I also make
> a lot
> of glaze tests and I just dump the ones I don't like into a bucket,
> just
> like you. Over many many years, I've come to count on the scrap always
> being a semi-transparent deep green with speckles. It may very a bit
> if I
> test and dump lots of tests of a similar glaze, but a random
> accumulation
> will pretty much always be like this. ...Paul Lewing, Seattle
>
Paul Lewing on fri 27 may 05
on 5/26/05 9:18 PM, Tig Dupre at marcy.dupre@US.ARMY.MIL wrote:
> The glaze came out of ^6 a beautiful,
> semi-transparent, deep-green, with speckles in it, probably from the
> ash I used in several test glazes.
Tig, I create and use a lot of scrap glaze in my process. I also make a lot
of glaze tests and I just dump the ones I don't like into a bucket, just
like you. Over many many years, I've come to count on the scrap always
being a semi-transparent deep green with speckles. It may very a bit if I
test and dump lots of tests of a similar glaze, but a random accumulation
will pretty much always be like this. If it's not, it will be so close that
only a little experimentation will make it so.
So my advice would be, don't waste your money on testing. What you have is
that bucket is likely so complex, with so many traces of so many different
things, that no analysis is going to tell you closely enough what it is for
you to duplicate it. You don't really care what the formula is- you just
want to repeat this. I don't think that will be a problem. Just keep
saving your scraps.
Paul Lewing, Seattle
Louis Katz on fri 27 may 05
Glaze up a couple of hundred tiles. Offer them to anyone who wants a
chance at $15,000 for $150. When you have sold 170 of these people can
try and duplicate the glaze. Hire me as judge and get payed $3000 for
judging. The remaining $15,000 goes to the winner. You get the glaze
recipes.
Good luck.
Or take some real good quality pictures of the glaze as you have it.
Post em to the web and ask people how to make a glaze like it.
Louis
On May 27, 2005, at 5:27 PM, Paul Lewing wrote:
> on 5/26/05 9:18 PM, Tig Dupre at marcy.dupre@US.ARMY.MIL wrote:
>
>> The glaze came out of ^6 a beautiful,
>> semi-transparent, deep-green, with speckles in it, probably from the
>> ash I used in several test glazes.
>
> Tig, I create and use a lot of scrap glaze in my process. I also make
> a lot
> of glaze tests and I just dump the ones I don't like into a bucket,
> just
> like you. Over many many years, I've come to count on the scrap always
> being a semi-transparent deep green with speckles. It may very a bit
> if I
> test and dump lots of tests of a similar glaze, but a random
> accumulation
> will pretty much always be like this. If it's not, it will be so
> close that
> only a little experimentation will make it so.
> So my advice would be, don't waste your money on testing. What you
> have is
> that bucket is likely so complex, with so many traces of so many
> different
> things, that no analysis is going to tell you closely enough what it
> is for
> you to duplicate it. You don't really care what the formula is- you
> just
> want to repeat this. I don't think that will be a problem. Just keep
> saving your scraps.
> Paul Lewing, Seattle
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
Louis Katz
http://www.tamucc.edu/~lkatz
Louis Katz on sat 28 may 05
We get this color more often than not as well from our scrap. Lately
however a few things have tipped our scrap towards other effects. One
is a bucket of lichen glaze full of magnesia which when added to our
scrap gave us a wonderful glaze glossy but matt in pools. A copper
Bearing Raku glaze gave our celadon-like scrap the ability to go muddy
red at times. I reproduced this in the next bucket with a handfull of
Copper Oxide. One of my current favorite additions to scrap glazes are
titanium minerals.
I am going to stop collecting small quantities of scrap. I want to fill
a 20 gallon bucket and then alter it to make it look nice. This way it
can last us long enough to learn how to use it well.
At the school here we give scrap glazes colorful names. Buffalo Eye,
Midnight in Montana, Oso Lavender etc. Students are much more likely to
use them if we don't call them Scrap.
Louis
On May 27, 2005, at 10:17 PM, Gail Dapogny wrote:
> In our guild, each week we scrape down the back and sides of the spray
> booth. and collect the scrapings in a bowl, free to anyone who wants
> it. Many use it for the insides of pots where the outside is more
> important than the inside. We have done this for...decades. It
> comes out pretty much exactly as Paul has described, sort of a celadon
> but deeper.
> interesting, huh?
> Gail
>
> Gail Dapogny
> Ann Arbor, Michigan
> http://www.pottersguild.net/
>
> On May 27, 2005, at 6:27 PM, Paul Lewing wrote:
>
>> on 5/26/05 9:18 PM, Tig Dupre at marcy.dupre@US.ARMY.MIL wrote:
>>
>>> The glaze came out of ^6 a beautiful,
>>> semi-transparent, deep-green, with speckles in it, probably from the
>>> ash I used in several test glazes.
>>
>> Tig, I create and use a lot of scrap glaze in my process. I also make
>> a lot
>> of glaze tests and I just dump the ones I don't like into a bucket,
>> just
>> like you. Over many many years, I've come to count on the scrap
>> always
>> being a semi-transparent deep green with speckles. It may very a bit
>> if I
>> test and dump lots of tests of a similar glaze, but a random
>> accumulation
>> will pretty much always be like this. ...Paul Lewing, Seattle
>>
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
Louis Katz
http://www.tamucc.edu/~lkatz
Ann Brink on sat 28 may 05
My best success in improving that "greenish" color has been to add
opacifiers, which improve the color a lot. I added cobalt & Ultrox to one
bucket, and got quite a nice turquoise. And I sort of like the specks, in
fact I'm on a speck kick with my other glazes too. I got some material from
a hillside near Alturas CA, which turns out to be in the volcanic ash
family, and I have added some to various glazes. It is insoluble enough to
not just evenly darken the glaze, so I am getting these soft freckles, and
sometimes the iron-spot look (in oxidation).
Good firings,
Ann Brink in Lompoc CA
> Louis wrote:". One of my current favorite additions to scrap glazes are
> titanium minerals.
>
> I am going to stop collecting small quantities of scrap. I want to fill
> a 20 gallon bucket and then alter it to make it look nice. This way it
> can last us long enough to learn how to use it well."
>
Craig Martell on sun 29 may 05
Tig asked:
>Can someone recommend a lab in the USA I could send a sample of the glaze
>to? And could you
>give me an approximation of how much it would cost? Also, would it help
>if I told the lab what I remember of the materials that went into the
>various glazes?
Hi:
I haven't seen an answer to this ? yet so I'll tell you what I know.
If you want to go ahead with this plan, I would recommend an XRF analysis,
which means X-Ray flourescense. This will give you a percentage of all the
oxides present. You will then have to calculate the glaze recipe from
this. You already know what materials and minerals you've used so you can
calculate using that knowledge. An XRD or X-Ray Diffraction analysis would
tell you what minerals are present but this more expensive if I remember
correctly.
For an XRF, you need to send a small amount of the dry glaze screened thru
a 100 mesh. It's an easy preparation, no special stuff to do.
I haven't had an XRF done for a few years and my guess would be plus or
minus $100 bucks. I could be out to lunch on that one though. You'll have
to check.
You might try some Geology Departments at colleges near you. They will
sometimes have the equipment and would do the analysis. You can also use
Google to find a lab. I don't have a lab at present or I'd tell you who I
use. If you have trouble finding something you might call USGS Dept of
Mineralogy and ask for some help.
regards, Craig Martell Hopewell, Oregon
Edouard Bastarache Inc. on mon 30 may 05
Paul,
here are texts by experts in the field :
Here we use X-ray fluorescence spectrometry (XRF) and atomic absorsion
spectroscopy (AAS) routinely on raw material analyses. AAS is perfectly
quantitative in the right hands! :) These methods report elemental
compositions. Molar composition of the respective oxides can be spat out by
the computer programs controlling both analytical methods.
The raw sample is usually pulverised and formed into a pressed powder
tablet, or fused into a glass disk with a suitable analytical-grade flux for
XRF. For AAS, the pulverised sample is digested (dissolved into solution)
by mixtures of strong acids, normally perchloric and hydrofluoric acid.
Only a few problematical elements cannot be accurately analysed by XRF or
AAS. These are not common in ceramic materials. These few elements are
analysed by other methods such as inductively coupled plasma spectroscopy
(ICP), neutron activation analysis (NAA), or the old fall-back position -
wet chemical analysis. Individual microscopic minerals can be analysed
in-situ in a rock by electron microprobe, or x-ray microprobe, which is
virtually micro-XRF.
XRF works by beaming x-rays onto the sample which excites the electrons in
the atoms of the elements present, to move to higher energy orbitals. The
electrons jump up to the higher orbitals in set steps, called quanta. The
over-excited electrons cannot party-on forever at these elevated energy
states and cascade back to lower orbitals closer to the nucleus. When they
fall back, they emit a x-ray photon (secondary x-rays) which is detected as
a flash of light on a special crystal inside the XRF machine. The energy
emitted as secondary x-ray photons is specific to the element to which the
electrons belong and the particular orbital they occupy. The flashes of
light (fluorescence) are passed through a photomultiplier and analysed by a
detector. The computer sorts out the amounts of particular energy photons
present and converts this by way of complex matrix computations into an
elemental analysis... whew!
AAS works by beaming light of a set frequency through a flame into which an
aqueous solution of the sample has been vaporised. In this case (similarly
to XRF), the orbital electrons absorb certain quanta of light from the beam
in order to jump up to higher energy levels. Very specific frequency photons
are absorbed by this process and the detector (opposite the light source)
measures the loss and again the clever computer calculates the amount of the
particular element stealing the photons. Light from the sun and stars has
numerous dark bands in the spectrum of light emitted, which is the same
process. The dark bands are specific energy (= frequency) photons that have
been absorbed by specific elements in the suns (or stars) atmosphere.
Spectral analysis of sunlight reveals exactly what elements are present in
the solar atmosphere by this method, which is virtually long-distance AAS.
Michael Banks,
Nelson,
New Zealand
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
The chemical analysis is done in terms of mass (so-called "weight," though
not really that). But thanks to Avogadro's number, we can readily convert
from mass to the number of atoms or molecules. The number of molecules in
one gram-mole of a substance, defined as the molecular weight in grams, is
6.022 times 10 to the 23rd power--which is Avogadro's number. For example,
the molecular weight of oxygen is 32, so one gram-mole of oxygen has a mass
of 32 g and contains 6.022 x 10^23^ molecules. Isn't that conversion
amazing?
Many techniques are used for analysis of chemical elements, depending on
the level of accuracy required, the equipment on hand, and so forth. For a
good description of available techniques, see the Encyclopedia Brittanica's
Macropedia, under Analysis and Measurement. An ordinary, relatively
inexpensive analysis provides values good to two (or three) significant
figures, and that's probably all the accuracy you can expect --or need--
for most pottery work.
The most accurate apparatus now being used for routine chemical analysis is
the high-resolution mass spectroscope, which can resolve a difference as
small as one part in 10,000,000. With that kind of precision, you can tell
the masses not just of chemical elements but of the various isotopes of an
element, e.g. carbon-12 vs. carbon-14, or hydrogen vs. deuterium vs.
tritium. (In our work on baboons, we use this apparatus to analyze
quantitatively for the rare isotopes of hydrogen and oxygen, in order to
estimate the animals' rate of energy expenditure -- but that's another
story.)
("In the unity part of a formula there are parts of a molecule listed for
each oxide...") No, a unity formula does not indicate the number of
molecules or parts of molecules. It indicates the relative amounts
(proportions) of the listed oxides. This common confusion would be avoided
if unity formulas were expressed as percentages instead of proportions--but
that would probably lead to a different confusion, of thinking that these
are the percentages of oxides in your recipe.
Paul asks, "Do they take many samples from different parts of the mine...Is
it different for more consistent materials?"
The more heterogeneous the material, the larger the sample size needed to
achieve any given degree of accuracy in estimating mean composition.
Getting representative samples is fraught with potential biases; much
attention has been directed to methods for minimizing them. Do mining
companies make use of modern sampling methods? Ah, thereby hangs a tale!
Stuart Altmann
Princeton
Paul Lewing on mon 30 may 05
on 5/29/05 8:09 PM, Craig Martell at ashglaze@WVI.COM wrote:
> An XRD or X-Ray Diffraction analysis would
> tell you what minerals are present
Craig, I believe (although this is based on my one class in clay mineralogy
in 1971) that X-ray diffraction only identifies clay minerals. It works by
measuring the distance between layers in a layered lattice material like
clay. If there is a mixture of clay minerals, it will tell you what
minerals are present, but not amounts. I don't think it can identify stuff
like whiting or feldspar.
By the way, one thing we found out in that class when we analyzed every clay
we could get our hands on was that, according to the X-ray diffractometer,
all the kaolins, all the ball clays, and all the fire clays were the same
mineral- b-axis disordered kaolinite.
Bottom line: Craig's right as usual. You want XRF if you decide to go for
an analysis, but I still think it would be a waste of money.
Paul Lewing, Seattle
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