Robert Speirs, M.D. 766 X4450 on mon 2 jun 97
Help, all you kind and wonderful glaze gurus!!
Here's the offending glaze:
Rutile Pink ^6
Custer 28
Whiting l4
Dolomite l4
Zinc ox l0
Lithium 3
Flint 20
Rutile 7
Bentonite 4
I stupidly (altho I'm still kind of new at this) made a 5 gallon bucket
(20 lbs dry materials) of this glaze based on a test of l00 gms. The
test yielded a beautiful satin fleshy pink with striations of gold and
white throughout the glaze.
When I glazed my first piece from this bucket, I got a glassy clear that
was horribly cratered that ran completely off the pot onto the shelf
(thank god for kiln wash!) into a puddle. There was a baby blue ring and
only a tiny area of the pink that looked like my test in the puddle.
My feeling is that this glaze needs some kind of stiffener (alumina??)
but I really don't know how to proceed in salvaging all this glaze. Any
ideas you have would be more than appreciated by me.
Thanks for your input. I owe you.
Laura in Oregon
Louis Katz on tue 3 jun 97
Sounds like you probably mixed up the glaze wrong, but those 100gram test
can be very iffy. If I intend to actually mix after my tests in any
sizable quantity I start with 300 grams or more.
Anyhow adding a kaolin will stiffen your glaze,It looks like your glaze
is designed to be lowish in Alumina, (I'll let someone else with more
knowledge of limits address this. The Kaolin will probably help this
glaze's application also. It has no clay other than the bentonite. It
wouldn't suprise me if the addtional clay changed it's color response
also.
I wrote a short answer for the NCECA journal on fixing scrap glazes. It
is not up on my website yet, but should be sometime this summer.
Louis Katz
Texas A&M University Corpus Campus
lkatz@falcon.tamucc.edu
http://www.tamucc.edu/~lkatz
Lawrence Ewing on tue 3 jun 97
>My feeling is that this glaze needs some kind of stiffener (alumina??)
>but I really don't know how to proceed in salvaging all this glaze.
Laura,
You are correct in assuming that your bulk mix needs alumina. In fact an
analysis of the recipe you posted suggests that you may have left the
clay componant out of the recipe as the levels of both alumina and silica
are way too low for cone 6. If the 100 gramme test was OK then you may
have left out the clay when you mixed the bulk recipe.
One approach to fixing the posted glaze might be to run a line blend
increasing the amount of clay in the recipe up to maybe 50% total. You
could do this by mixing another 100 gramme test batch of the offending
glaze and adding 10 grammes of clay at a time (dipping a test tile each
time) until you get up to a total of say 50 grammes additional clay.
Regards,
Lawrence Ewing
Lecturer in Ceramics
School of Art
Otago Polytechnic
lewing@clear.net.nz
21 Slant St
Careys Bay
Dunedin
NEW ZEALAND
ph (03) 472 8801
Author of MATRIX Glaze Calculation Software for Macintosh
DonKopy@aol.com on tue 3 jun 97
Hi Laura,
What you've got is best described as a "bucket-o-flux".
It is very high in flux and lacking in both alumina and silica.
My best shoot from the hip fix would be to add an additional
20 EPK
25 Flint
2.2 Rutile
This will provide the silica and alumina needed to make it a "glaze".
Will it be exactly the same as your test? Probably not quite, and you might
lose the pink (the striations would most likely be gone, as the excessive
fluidity is partly their cause). Titanium promotes crystallization in low
alumina glazes. I have seen this pink in low alumina compositions,
particularly in thick areas where the glaze pools
>>( only a tiny area of the pink that looked like my test in the puddle.)<<.
Your best bet for the pink would be to slow the cooling a bit. If you don't
get a color you can live with, perhaps adding cobalt carb. in increments of
1/2 % will yield a broken blue glaze that would be interesting with some
activity and break-up.
Anyone concur?
------------------------
>> Here's the offending glaze:
Rutile Pink ^6
Custer 28
Whiting l4
Dolomite l4
Zinc ox l0
Lithium 3
Flint 20
Rutile 7
Bentonite 4
<>
>> When I glazed my first piece from this bucket, I got a glassy clear
that
was horribly cratered that ran completely off the pot onto the shelf
(thank god for kiln wash!) into a puddle.<<
Hope this fix makes the glaze usable,
Don Kopyscinski
Bear Hills Pottery
Newtown, CT
NAME on wed 4 jun 97
Mary,
Did you calcine the zinc oxide? If not terribe things like what you mentioned
could easily take place.
good luck - J. SCHMUKI
Craig Martell on wed 4 jun 97
At 08:58 AM 6/2/97 EDT, Laura in Oregon wrote:
>----------------------------Original message----------------------------
>
> Help, all you kind and wonderful glaze gurus!!
>
> Here's the offending glaze:
>
> Rutile Pink ^6
>
> Custer 28
> Whiting l4
> Dolomite l4
> Zinc ox l0
> Lithium 3
> Flint 20
> Rutile 7
> Bentonite 4
Hi Laura:
When you did your test, did you fire the glaze on a flat tile, or on a
vertical one? I'm just curious because if you fired it on a vertical tile,
why the big difference in the glaze. The cratering was probably due to
overfiring.
I would assume that you haven't used much of the 5 gal batch so you can
probably estimate the weight of the materials when you find the correct
additions. You should mix up separate tests and blend in kaolin at 5%
increments until the glaze is not running off the pot. Another way to do
this, is to mix the glaze as is, without any additions, dry, and sieve it
about 3 or 4 times through a 50 mesh screen to homogenize the mix. Then do
a triaxial blend with kaolin and silica to find the glaze that you want.
You can do the triaxials on a flat tile and vertical ones as well, to check
the fluidity of the glaze. There are lots of books that explain how to do a
triaxial blend if you haven't had experience with this. The Ceramic
Spectrum by Robin Hopper covers this.
Regards, Craig Martell
David Hewitt on wed 4 jun 97
I would have thought that this recipe was indeed short of alumina and
silica as you suspect. In fact, adding 50 parts of china clay to the
recipe makes it look far more probable. A line blend from 20 parts to
50 parts of china clay might be a way of finding workable glaze.
In message , "Robert Speirs, M.D. 766 X4450"
writes
>----------------------------Original message----------------------------
>
> Help, all you kind and wonderful glaze gurus!!
>
> Here's the offending glaze:
>
> Rutile Pink ^6
>
> Custer 28
> Whiting l4
> Dolomite l4
> Zinc ox l0
> Lithium 3
> Flint 20
> Rutile 7
> Bentonite 4
>
> I stupidly (altho I'm still kind of new at this) made a 5 gallon bucket
> (20 lbs dry materials) of this glaze based on a test of l00 gms. The
> test yielded a beautiful satin fleshy pink with striations of gold and
> white throughout the glaze.
>
> When I glazed my first piece from this bucket, I got a glassy clear that
> was horribly cratered that ran completely off the pot onto the shelf
> (thank god for kiln wash!) into a puddle. There was a baby blue ring and
> only a tiny area of the pink that looked like my test in the puddle.
>
> My feeling is that this glaze needs some kind of stiffener (alumina??)
> but I really don't know how to proceed in salvaging all this glaze. Any
> ideas you have would be more than appreciated by me.
>
> Thanks for your input. I owe you.
>
> Laura in Oregon
>
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP6 1DQ, UK. Tel:- +44 (0) 1633 420647
URL http://www.ceramicsoftware.com/education/people/hewitt.htm
Ray Carlton on wed 4 jun 97
At 08:58 AM 02/06/97 EDT, you wrote:
>----------------------------Original message----------------------------
>
> Help, all you kind and wonderful glaze gurus!!
>
> Here's the offending glaze:
>
> Rutile Pink ^6
>
> Custer 28
> Whiting l4
> Dolomite l4
> Zinc ox l0
> Lithium 3
> Flint 20
> Rutile 7
> Bentonite 4
>
> I stupidly (altho I'm //snip
i think you made a boo boo in your batch conversion or your scales need
calibrating
Ray Carlton McMahons Creek Victoria Australia
raycarlt@ozonline.com.au
Greg Lamont on fri 6 jun 97
Laura,
I am a student at Iowa State University, so I don't consider myself a "glaze
Guru" but I'll give you my thoughts and see how they fare against the pros.
I have been using Robert Wilt's glaze chemistry/calculation software
_GlazeChem_. Based on the limit
formula tables it provides, I ran your glaze through and it came out as
being too high in MgO and Zinc and way too low in alumina for a ^5/6
semi-matte glaze. ( It was a good ^04). I made some adjustments to arrive
at a balanced satin matt according to the limit formulas for a ^5/6 semi matt :
31 Custer feldspar add: 7 Rutile
10 Whiting 2 Bentonite
10 Dolomite
7 Zinc
2 Lithium
28 Flint
12 EPK
___
100
Test this and tell me what you think. I am also working at ^5/6 oxidation
and would be happy to share recipes.
Good luck,
Greg
----------------------------Original message----------------------------
Help, all you kind and wonderful glaze gurus!!
Here's the offending glaze:
Rutile Pink ^6
Custer 28
Whiting l4
Dolomite l4
Zinc ox l0
Lithium 3
Flint 20
Rutile 7
Bentonite 4
(Rest snipped)
| |
|
