bill edwards on fri 3 mar 06
I had asked David Hewitt to run the formulation for
the recipe Stormy Lavender Blue, a decorative glaze as
it stands and may craze on some clays. I think there
will be more additional calculations down the road so
you can see why we need recipe as well as molecular
information. Molecular is only as good as the imput
information while the recipe as it stands can be
hashed over by good researchers and a common sense end
can usually be found. This glaze took countless
firings and physical tests to get the color I wanted
that made her happy. Her daughter thought it was a
great to honor her mother and it is for decorative use
as far as I am concerned regardless of what oxides you
choose down the road. It will leach where acidics are
left over a period of time but is graceful and pretty
and doesn't have surface flaws on the clays I have
used it on. Those clays will be Lagunas B-Mix 5/6.
Porcelain, 181 a higher fire was done with that clay
for testing purposes.
The challenge - if there is someone who can change
this glaze to where the coloring oxides can't be
pulled from a lab and make it food surface grade, I am
all for it. I would love to see that done especially
where the charector and color of the glaze is kept.
Its a satin-egg shell finish with specks of blue and a
lavender frost just in case anyone wants to tackle
something like that. However, there is no known need
to do this unless your using it specifically for food
bearing products where acidics are going to set. But
we aren't all into just making food bearing glazes.
That choice is yours to make, the recipe is there for
change but lets not change it for awhile because then
we will have countless versions running around and it
will just add to the confusion unless those making
their additions add on their information and point
back to the origin recipe.
David's calculation is below. Then I will give the
manufacturers feldspar informationa after his
calculations because several have stated they do not
have NC4's information. Zemex Corperation is the
source for their NC 4 analysis,a feldspar corperation.
They make many products that wind up on the market for
clay lovers.
Unity for Stormy's Lavender Blue
Source: Bill Edwards
Unity on 03.03.06 David Hewitt
Cone ^6 ox.
See recipe for compound details.
The recipe you gave comes out as follows with
CeramDat. (Cedited to David Hewitt)03/03/06
Unity Formula
K2O .042 Al2O3 .301 SiO2 2.958
Na2O .227 B2O3 .121 TiO2 .001
CaO .319 Fe2O3 .002 P2O5 .001
MgO .412
COE 4.390 English & Turner or 6.674 McLindon or
6.253 Appen
all these are x10-6/oC Linear
Al2O3 / SiO2 1/9.83
Surface Tension 369.973 dyn/cm
http://www.z-i-m.com/PDS/NC4250Feldspar.pdf
In the future we will see other calculations which
will lend more credit to the reasons we need to work
with both the recipe as well as the molecular
formulation. Then we will have a more complete picture
of this story and what I believe is a better education
in my own opinion, as I have one.
Where there are shifts and differences in opinion on
molecular analysis based on drifts and variance in
imputted information, the recipe remains stable, good
or bad. That means you have the option of double
checking against the company materials and QC'ing the
source and running all that over again through various
softwares to see how well you do. You do have to use
both the recipe and calculations hand in hand to
reduce the time you'd spend in physical testing. If
you are a stickler for detail you can get there
quicker by having several methods to test from before
you embark on production runs of any kind. I would
never suggest you use one source regardless of how
well you believe they are educated. Comparitive
studies are vital to growth and understanding, you
need a complete picture. I wouldn't want anyone to use
anything I do as a sole source for information. It
would not be good for me or for anyone else.
Here's some helpful information and I believe it is
all educating.
Write down the names of each company that manufactures
each component of the glazes you use.
Get software for glaze formulae calculations.
Learn to put the manufacturers information in there.
Check the currect analysis.
Fire original source recipes only if you are looking
for the same results or similar results the origin
stated they were getting.
Pay attention to any of the firing techniques they
describe.
Do not follow someone else's fixes until you have
exhuasted the above through proper testing because
they may not always be on the money or giving you full
attention, you send it to the labs when you make
changes you believe are to your benefit, inparticular
those that will be used for food bearing surfaces
regardless. (This means you have made several test
samples and fired them side by side and kept notes)
You are protecting your investment by doing 3rd party
research and development which shows good faith and
craftmanship and an interest in others well being and
your product.
Education comes in many forms, complete discussion
among peers is the best method for getting information
off the table and into practice. Being professional
with professionals and hobbiest's alike is key to
preserving the integrity of our craft and pulling it
up another notch as the years tick by.
A decorative glaze may be made better in some
circumstances and still be as viable (look, feel,
aesthetics etc) as the original, not always. In the
rush to remove a once well used product, 'Gerstley
Borate' many recipe conversions were discovered and
change took place, some didn't work at all. I give
gerstly a big hand because it taught many potters what
they know now. This major market shift forced change.
There were countless disasters that followed with many
subbed materials being put out on the the market. It
took physical testing and lots of calculations and a
good eye to correct that loss and we are still trying
to replace many of those glazes. Floating Blue is an
example that still comes and goes and there's been
super guru's who have failed in getting that glaze to
a state of perfection where it can be expected to fire
true day in and day out. So a shift in our roles have
came into play and as potters we needed to have tools
we could work with less being overlyt specific as to
how those are used. There's too many mistakes to be
made through other people advice without taking the
BIG picture into view. That method has never worked
except where I have been in manufacturing and is ran
with lab experts and very tight QC and there's still
mistakes made on the best days where analytical
problems arise. At least the origin or the recipes can
put us back into business and we can use that to
eliminate the problems through proper channels and QC.
My gratitude goes out to David Hewitt for his work and
time and calculations. Please, others who wish to do
this do the same and send me your results so I can
help some understand my processes as well. I believe
David will provide you factual information as to his
standards he used and no part of his calculations were
changed or altered. This benefits the readers. Now
there will be changes coming from others as we
progress because there are differences in how
calculations are done and how the software processes
this information and those will alter the molecular
structure of the base (differing results)we started
here with, what remains in-tact... The recipe its
self. So I believe we must work from having a recipe
and all the calculations others may make because that
is where we will find our answers and fine tune our
results to market specific ends.
Bill Edwards
http://apottersmark.blogspot.com/
'Studio Pottery Set-up for Sell, offers considered!'
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