Emily & Kurt Kiewel on sun 19 sep 99
>----------------------------Original message----------------------------
>Hi Emily,
>
>Send this back to me but with as detailed a description of the clay as
>possible. Are you firing oxidation - Tell me how long a firing you do -
>particularly from red heat to cone 10 - and describe the cracks - the
>pattern and tell me if there is any difference after freezing in your
>fridge for 24 hours - put one that did not craze in as well. RR
The Clay: Balcones from Armadillo in Austin, Texas. Cone 10, approximately
12% shrinkage, gets nice brown color when fired in reduction. No grog.
Pretty plastic.
Firing: Reduction, time from red heat (approx. 800 C) to end of firing-7
hours and 45 minutes. The total firing time is usually 12 hours.
The cracks: Not under a lot of tension. Few and spread out. On one plate
they start in the center and radiate out about 1 1/2 inches, looks like the
beginnings of a spiderweb. On another plate there are a few more and they
don't begin so centrally. They do radiate out to the beginning of the lip
though. There is also another crack that goes around the diameter of the
plate right where it curves up to the lip, at the base of the curve-where
all the other cracks end. There are no cracks on any lips which are 1 1/2
wide.
The freezing: I've just put the two plates I described in the freezer
along with a dinner plate that did not craze and a salad plate for good
measure (4 PM). I'll let you know tomorrow how it looks.
Thanks so much for responding! My anxiety has lessened quite a bit already
after reading the responses from you and Tom B. I feel sure I'm receiving
the best help possible!
Emily
In College Station, Texas where my neighborhood has gone nuts. I think
there is a home football game tonight (American football). Everybody is
dressed alike in maroon and white and parking is becoming more and more
scarce (I live less than an mile from the football field). Can anyone
guess the team? ;)
Ron Roy on wed 22 sep 99
Hi Emily,
I suspect the opposite of crazing - probably from some cristobalite in the
body - those cone 10 reduction bodies with iron always have that
possibility.
So here is what you do. Mix up 500 grams of your original glaze and 500
grams of the glaze below - put each on a plate and then mix both glazes
together and put on a third plate - fire in a normal firing - top or middle
of your kiln and we shall see. Don't forget to do the freezing/ boiling
thing after and get back to me - and include the recipes - I don't save
them at this end.
Rons revision with higher expansion call it #C call your #A and the
combination #B
-----------------
F4 SPAR...................47.00 (your min spar is OK - do you ahve an
analysis for it?)
WHITING.................22.00
EPK...........................10.00
SILICA......................22.00
BENTONITE..............2.00
RED IRON OX..........1.50
----------
Total......................104.50
RATIO 7.50 (your original is 8.82)
EXPAN 543.87 (Your original is 486.97)
WEIGHT 298.36 (your original is 333.66)
>
>The Clay: Balcones from Armadillo in Austin, Texas. Cone 10, approximately
>12% shrinkage, gets nice brown color when fired in reduction. No grog.
>Pretty plastic.
>
>Firing: Reduction, time from red heat (approx. 800 C) to end of firing-7
>hours and 45 minutes. The total firing time is usually 12 hours.
>
>The cracks: Not under a lot of tension. Few and spread out. On one plate
>they start in the center and radiate out about 1 1/2 inches, looks like the
>beginnings of a spiderweb. On another plate there are a few more and they
>don't begin so centrally. They do radiate out to the beginning of the lip
>though. There is also another crack that goes around the diameter of the
>plate right where it curves up to the lip, at the base of the curve-where
>all the other cracks end. There are no cracks on any lips which are 1 1/2
>wide.
>
>The freezing: I've just put the two plates I described in the freezer
>along with a dinner plate that did not craze and a salad plate for good
>measure (4 PM). I'll let you know tomorrow how it looks.
>
>Thanks so much for responding! My anxiety has lessened quite a bit already
>after reading the responses from you and Tom B. I feel sure I'm receiving
>the best help possible!
>
>Emily
>In College Station, Texas where my neighborhood has gone nuts. I think
>there is a home football game tonight (American football). Everybody is
>dressed alike in maroon and white and parking is becoming more and more
>scarce (I live less than an mile from the football field). Can anyone
>guess the team? ;)
Ron Roy
93 Pegasus Trail
Scarborough
Ontario, Canada
M1G 3N8
Evenings 416-439-2621
Fax 416-438-7849
Emily & Kurt Kiewel on fri 24 sep 99
I was planning a firing for tomorrow, so I will be mixing up glaze A, B,
and C today. Thanks-I'm excited to see the results. I'll let you know how
they do. What is the boiling thing? I think I missed that in previous
emails. Should I boil the plates for an hour before putting them into the
freezer? I also have access to an autoclave (only 20 PSI though).
Here is the chemical analysis for Minspar 200
SiO2 67.9
Al2O3 19.2
Fe2O3 0.06
CaO 1.5
MgO trace
Na2O 6.9
K2O 4.1
L.O.I. 0.3
More later-Emily
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