Jeff Lawrence on wed 26 nov 97
Lance Philip Strugar is facing the same problem I am, namely:
> Re: Lowering the expansion on cone 5 clear
>
>----------------------------Original message----------------------------
>I've been trying to develop a good clear glaze for a white
>stoneware clay rated at cone 4 - cone 8. The manufacturer
>is L=26R SPECIALTIES Inc in Nixa Missouri. I bisque to =5E06
>and glaze to =5E5.
Lance,
I've fit a variation of Tony Hansen's glaze to a ^4-^7 clay from Mile-High
in Denver, after getting same crazing with his original recipe. I bisque to
^04, fire to ^5 and ^6 in oxidation. The recipe I'm using now with success
is listed below as Recipe 1.
Like you, I tried to lower the expansion with lithia in the mix but unlike
you, got no joy. I deduced that lithium carbonate doesn't have the same
effect at ^5 and ^6 that it does at higher temps.. But your spodumene
additions did help. Mighty confusing.
If anything, my tests with the lithium carb looked a lumpy -- whether
unmelted or poorly mixed wasn't clear.
Anyway, my brilliant insight of using 3195 for 3134 came from the following
incisive steps:
(1) Wrote down the numbers of the frits I had on hand
(2) Blindly subbed them in for 3134 in Insight
(3) Saw what lowered the expansion
(4) tinkered the changed ones (mainly lowered the EPK and upped the flint).
Just for fun, check out the same recipe with 3134 back in for 3195, Recipe
2. My current project is to get this glaze looking like all those delectable
sounding oxidation temmokus people have been generous enough to share (the
ones with the big fat expansions). Unfortunately, both iron oxide and
titanium dioxide raise the expansion, and I really like titanium
microcrystalline texture and slaver for a hares fur with little crystals,
maybe golden flecked, in it. I've got tests firing tonight ... surely this
time one will be perfect!
Jeff ... i'm not a potter, but I play one in cyberspace!
RECIPE 1
CONE 6 Clear Base Glaze - 61D195 (6MOF1D5)
==========================================
WOLLASTONITE........ 7.61 21.98%
EPK KAOLIN.......... 3.04 8.79%
FLINT............... 8.75 25.27%
CUSTER FELDSPAR..... 7.61 21.98%
FERRO FRIT 3195..... 7.61 21.98%
========
34.62
CaO 0.81* 13.31%
MgO 0.00* 0.01%
K2O 0.08* 2.27%
Na2O 0.11* 2.00%
Fe2O3 0.00 0.11%
TiO2 0.00 0.03%
B2O3 0.25 5.11%
Al2O3 0.33 9.94%
SiO2 3.80 67.21%
Cost/kg 0.69
Si:Al 11.48
SiB:Al 12.24
Expan 6.65
Notes:
Taken from Tony Hansen's "Magic of Fire", his balanced Cone 6 glaze
fired on clay ASH bisq 04 suffered delayed crazing
notes
10/21 sub'd 3195 for 3134 to lower coe, reduced EPK to enhance fluidity and
increased flint to lower coe
10/31 lowered Al203 & Si02 to get 6.78 -- maybe better flow will mean
better fit
11/4 -- looks good - better flow than previous; lowered fluxes appear to be
okay -- lithium carbonate additions of .04 and .1 brought no discernable
improvement in flow. Color tests pending
11/10 - removed .38 bentonite -- suspicicious of speckies
RECIPE 2
===============================================
WOLLASTONITE........ 7.61 21.98%
EPK KAOLIN.......... 3.04 8.79%
FLINT............... 8.75 25.27%
CUSTER FELDSPAR..... 7.61 21.98%
FERRO FRIT 3134..... 7.61 21.98%
========
34.62
CaO 0.79* 15.27%
MgO 0.00* 0.01%
K2O 0.07* 2.27%
Na2O 0.14* 2.98%
Fe2O3 0.00 0.11%
TiO2 0.00 0.03%
B2O3 0.21 5.12%
Al2O3 0.20 7.18%
SiO2 3.23 67.03%
Cost/kg 0.73
Si:Al 15.85
SiB:Al 16.89
Expan 7.14
Jeff Lawrence
jml@sundagger.com
Sun Dagger Design
Rt 3 Box 220
Espanola, NM 87532
ph 505-753-5913
fax 505-753-8074
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