Denis Caraty on tue 17 oct 00
J'ai fait plusieurs calculs sur vos glacures :
1)T.E.C
REV C : 59.00 x 10-7
CR#4 : 49.26 x 10-7
Canadore : 58.25 x 10-7
Cela confirme vos calculs sur le coeeficient de dilatation.
2)Melting Temperature
REV C : 1234?C (^6)
CR#4 : 1209?C (^5)
Canadore : 1073?C (^3)
La glacure "Canadore" est "over fired" si vous cuisez ^6 ou ^7.
Cette glacure est donc tres active pendant la cuisson, elle se comporte
comme un puissant solvant des elements contenus dans la pate de vos
produits. Elle s'enrichit avec les composants de la pate (SiO2 en
particulier) et ses proprietes sont modifiees. Sa couche superieure est sans
doute restee normale, mais sa couche inferieure en contact avec la pate est
differente. C'est ce que certains d'entre nous appellent "la couche
intermediaire".
Apres cuisson, elle resiste mieux au "crazing test" car ses proprietes
mecaniques ont ete renforcees et qu'elles sont plus progressives dans
l'epaisseur de la glacure.
Votre pate a donc probablement un coeficient de dilation inferieur ou egal a
celui de vos glacures.
Vous pouvez tester l'effet "couche intermediaire" sur la glacure REV-C et
CR#4 en comparant ces deux glacures cuites une seconde fois dans votre four
a ^6-7. Apres une deuxieme cuisson elles seront plus resistantes, car la
dissolution de la pate au contact de vos glacures aura ete augmentee.
Denis Caraty
Societe : Faienceries de Gien
78, place de la victoire, 45500 Gien, FRANCE
Fax : (33) 2 38 67 92 36
dcaraty@gien.com
http://www.gien.com
-----Message d'origine-----
De : Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG]De la
part de Les Wright
Envoye : lundi 16 octobre 2000 22:04
A : CLAYART@LSV.CERAMICS.ORG
Objet :
I'm having difficulty understanding the relationship between the coefficient
of expansion of the clay body and that of the glaze. The glaze calculation
program that I use in determining expansion numbers is Insight and the
expansion numbers of oxides and materials used are those provided by Ron
Roy.
It is my understanding that Ron uses a dilatometer to measure the expansion
of
all the clay bodies that Tucker's sells and I have all these figures. Using
Insight, I can calculate the attendant glaze expansion.
Trough reading C.W.Parmelee and a couple of other sources, supposedly glaze
fit (no crazing, but good compression) should fall within 10% to 20% less
expansion than the clay body with 15% being optimal. I have lowered my
original clear glaze from c.o.e # 445.51 to 295.76 and yet it is still
crazes.
Obviously, I will keep lowering the c.o.e until the crazing disappears, I
don't know any other way of solving the problem. Does it have anything to do
with measured vs calculated and are the c.o.e numbers given for oxides and
materials so inexact that mathematical comparison is useless. And yes, I
know,
test-test-test!
I have rambled on far too long, in short, I need a great deal of help.
This is the original and adjusted version of the glazes above. I fire from
about c/6 to c/7 and use Orton standard cones in oxidation. I use Tucker's
MCS, but I have also tested these glazes on Pottery Supply House 910;
Tuckers's Smooth White, Mid Smooth Spec, 650, Mid Porcelain Five.
Two Recipes: REV C & CR#4
===========================================
G-200 FELDSPAR G200. 32.00 16.00%
WOLLASTONITE........ 28.00 14.00% 29.29 14.65%
F12 (FERRO3134)..... 24.00 12.00% 22.78 11.39%
STRONTIUM CARBONATE. 20.00 10.00% 3.45 1.72%
TALC................ 4.00 2.00% 6.51 3.25%
EPK KAOLIN.......... 48.00 24.00% 55.25 27.62%
SILICA.............. 44.00 22.00% 63.20 31.60%
CADYCAL............. 8.14 4.07%
MAGNESIUM CARBONATE. 11.39 5.70%
======== ========
200.00 200.00
CaO 0.53* 9.30% 0.57* 10.83%
MnO2 0.00 0.00% 0.00 0.01%
MgO 0.07* 0.90% 0.32* 4.37%
K2O 0.07* 1.94% 0.00* 0.13%
Na2O 0.10* 1.90% 0.06* 1.36%
Fe2O3 0.00 0.22% 0.00 0.25%
TIO2 0.00 0.08% 0.00 0.09%
B2O3 0.14 2.98% 0.21 4.99%
AL2O3 0.41 13.14% 0.34 11.74%
SiO2 3.31 61.97% 3.20 64.88%
P2O5 0.00 0.03% 0.00 0.03%
SrO 0.23* 7.54% 0.04* 1.33%
COST/KG 2.52 1.88
Si:Al 8.02 9.40
SiB:Al 8.35 10.02
EXPAN 445.51 295.76
PS: Here is a glaze that appears to be crazless on all the aforementioned
clay
bodies and its c.o.e is 426.23.
Go Figure! I test for crazing by submersing my glazed tiles into 20*cent.
Water after heating them in an oven by 50*cent increments with the started
point of 100*cent. Please explain why and how this can be so.
RED TEM C/6 CANADORE (STEVE)
TA = TEM REV A
============================================
F12 (FERRO3134)..... 12.00 5.08%
TALC................ 36.00 15.25%
SILICA.............. 52.00 22.03%
CADYCAL............. 34.00 14.41%
F-4 FELDSPAR........ 62.00 26.27%
BELL DARK BALL CLAY. 4.00 1.69%
BENTONITE........... 4.00 1.69%
RED IRON OXIDE...... 32.00 13.56%
========
236.00
CaO 0.41* 6.89%
MnO2 0.00 0.03%
MgO 0.41* 4.90%
K2O 0.05* 1.34%
Na2O 0.14* 2.58%
Fe2O3 0.30 14.41%
TIO2 0.00 0.03%
B2O3 0.40 8.35%
AL2O3 0.21 6.37%
SiO2 3.06 55.10%
SrO 0.00* 0.01%
COST/KG 1.60
Si:Al 14.70
SiB:Al 16.63
EXPAN 426.23
Notes:
THIS RECIPE FROM CANADORE ELIMINATES GERST BOR BY SUB CADY CAL. RED IRON IS
FORCED PHANTOM.
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