Ben on tue 10 aug 04
I'm looking for a test approach with a dolomite matte I'm working with. =
I overfired it recently (a ways past ^10) and it beaded up into a nice =
ashy/salt looking texture with some nice matte crystals(mmmmacro) where =
it was over a more fluid glaze. I thought it might have been the rutile =
affecting the overall matte(ie macro crystallization) so I tested that, =
but it is clearly a temperature issue. So I'd like to find the verge =
of mattness while still maintaining the high surface tension from the =
dolomite (though it may be the Si/Al ratio is involved as well) and =
potentially matte. I'm firing to ^10 on the bottom and ^8 on top. I'm =
thinking maybe a triaxial with a silica increase on one corner and a Mg =
drop on the other. As it is on the third. Any suggestions would be =
appreciated. Especially understanding on the Mg/Al/Si realtionship as =
it relates to surface. Also, it appears this is both fluid and matte =
???
Thanks,
Ben
45.00 Custer Feldspar
5.00 Whiting
25.00 EP Kaolin
25.00 Dolomite
7.00 Rutile
0.25 *Cobalt Oxide
0.48* CaO
0.34* MgO
0.13* K2O
0.05* Na2O
0.21 TiO2
0.42 Al2O3
1.78 SiO2
Incidentally, This is a cobalt green. (the rutile shifts it from =
purple at about 6%)
I also found another cobalt green the other day. Whoops the were =
supposed to be blue. It's to fluid by itself at ^ 8-10 but its a nice =
accent and could be adjusted. It's definitely the borate/rutile yellow =
with the cobalt as Ivor has pointed out long ago (it's in the archive's)
31.80 Custer Feldspar
0.70 Whiting
18.30 EP Kaolin
8.70 Silica
40.50 Frit 3134
Add:4% rutile
1% cobalt oxide
0.5 % cobalt carbonate=20
Ivor and Olive Lewis on wed 11 aug 04
Dear Ben,
Sounds to me as though the best way to go is to use Ian Currie's
methodology. Get his books or register for one of his workshops.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
May Luk on wed 11 aug 04
Hi Ben;
I'm working with high magnesium matte with cobalt with my glaze group. One
of the currie grid test results is here:
http://www.londonpotters.com/photos/glazetest.jpg
This is a high magnesium matte with 2% cobalt and 5% tin. [not the one I'm
having problem with on my other post] We are firing in 3 different kilns and
we'll review our results in the sept meeting. [cone 8 and up ox] I had
tested the same glaze with 2% cobalt and 7.5% titanium and I got a teal
green with gold speckles. The surface is very nice eventhough I overfired
it.
Following is the analysis if you are interested:
Na2O______0.043
K2O_______0.112
MgO_______0.446
CaO_______0.302
ZnO_______0.097
Al2O3_____0.347
Fe2O3_____0.007
SiO2______2.447
TiO2______0.002
Si:Al_____7.06
COE_______63.08
Regards
May
London, UK
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