Sharon31 on sat 9 sep 00
As a result of correspondence with Tom Buck and some tests I did after
that, I come to you with this idea:
FFFloating Blue
Opal Blue(Zakin)
speckles Blue gray.
(perhaps Sapphire blue)
Later in the letter, I will add them.
What do they have in common?
High alumina
Cobalt ox. 1 or 2%
Ruttile 4%
Red iron ox 0-2%
Any of them , when I applied on the bare clay turned out different than it
should be.
Speckle brown+green
Floating green,
And Opal green.
But when I applied them above clear glazes with low alumina, the result
improved.
I started with this combination:
Speckles blue Gray
==================
GERSTLEY BORATE..... 20.00 18.60%
NEPHELINE SYENITE... 20.00 18.60% The original recipe was with potash
feldspar my variation good for ^5 too
FRIT 3110........... 15.00 13.95%
BALL CLAY........... 15.00 13.95%
QUARTZ.............. 30.00 27.91%
IRON OXIDE RED...... 1.50 1.40%
TITANIUM DIOXIDE.... 5.00 4.65%
COBALT OXIDE........ 1.00 0.93%
========
107.50
CaO 0.42* 5.39%
MgO 0.12* 1.08%
K2O 0.06* 1.37%
Na2O 0.40* 5.58%
TiO2 0.28 5.07%
Al2O3 0.46 10.61%
B2O3 0.40 6.28%
SiO2 4.60 62.89%
Fe2O3 0.05 1.72%
Cost/kg 11.10
Si:Al 10.06
SiB:Al 10.93
Expan 7.45
4)DARK BLUE: 3COBALT OXIDE
Below, a glaze I posted too, lately I changed the barium carbonate into
Strontium carbonate(0.75of it, ) also a ^5 glaze basically
Koren 27
========
QUARTZ.............. 26.00 26.53%
WHITING............. 13.00 13.27%
ENGLISH KAOLIN(Puraf 5.00 5.10%
ZINC OXIDE.......... 10.00 10.20%
FELDSPAR soda....... 35.00 35.71%
BARIUM CARBONATE.... 9.00 9.18%
========
98.00
BaO 0.12* 7.80%
CaO 0.38* 8.80%
MgO 0.00* 0.02%
K2O 0.05* 2.04%
Na2O 0.11* 2.69%
ZnO 0.33* 11.16%
TiO2 0.00 0.01%
Al2O3 0.23 9.64%
SiO2 2.34 57.79%
Fe2O3 0.00 0.06%
Cost/kg 4.85
Si:Al 10.17
SiB:Al 10.17
Expan 7.71
Lately saw in Clay Times (I get it whenever my nice niece is sending it to
me) a
glaze of Paul Lewing.
I tested the glaze. The results can be a subject to another letter, but also
tested it, with less alumina.
Paul Lewing glaze with my local materials(local English, Norwegian, Spanish
and so on)
LEWING'S ZINC BASE^4-^6
=======================
SILICA.............. 25.74 25.74%
ZINC OXIDE.......... 11.10 11.10%
WHITING............. 7.86 7.86%
FRIT 6004........... 10.93 10.93%
ENGLISH KAOLIN(Puraf 29.14 29.14%
POTASH FELDSPAR NR.. 15.23 15.23%
========
100.00
CaO 0.27* 4.74%
MgO 0.00* 0.03%
K2O 0.16* 4.91%
Na2O 0.10* 2.04%
ZnO 0.46* 11.93%
TiO2 0.00 0.03%
Al2O3 0.36 11.58%
B2O3 0.14 3.00%
SiO2 3.23 61.49%
Fe2O3 0.00 0.25%
Cost/kg 6.03
Si:Al 9.01
SiB:Al 9.39
Expan 7.25
Maybe different than the original as...Local.
These two recipes are similar, except that Lewig base is more friendly.
Thank you Paul!
I decrease the alumina
Low Alumina Lewing
==================
WHITING............. 10.08 10.08%
ENGLISH KAOLIN(Puraf 23.25 23.25%
ZINC OXIDE.......... 14.23 14.23%
QUARTZ.............. 18.90 18.90%
FRIT 6004........... 14.01 14.01%
POTASH FELDSPAR NR.. 19.52 19.52%
========
100.00
CaO 0.27* 6.10%
MgO 0.00* 0.04%
K2O 0.15* 5.86%
Na2O 0.11* 2.62%
ZnO 0.47* 15.34%
TiO2 0.00 0.02%
Al2O3 0.23 9.47%
B2O3 0.14 3.85%
SiO2 2.34 56.50%
Fe2O3 0.00 0.20%
Cost/kg 6.79
Si:Al 10.13
SiB:Al 10.72
Expan 8.02
Notes:
Glossy translucent , with a bit of bluish cast.
Now the test: I use small saucers, I make them by pushing claybody into a
plastic saucer, so there are kind of "valleys and hills".
The clay was buff mottled German clay.
Floating blue: Blue in the "valleys" somehow light-brown in the "hills"
The same, but more interesting variations of color in speckles
gray-blue.(there is iron too)
Opal blue:blue in the valleys and... green on the hills.
On the next ^6 firing I will try this combination on terra cota.(Floating
blue)
I made one batch of speckle blue, with frit instead of G.B. turned almost
the same.
This combination can be very nice on textured surface!
I do not know if the Zinc plays here anything.
These of you that do not have a software might even try Tony Hansensv
20/5,(I don't have anymore frit 3134) decrease the kaolin into 10 increase
the silica to 30 or the wollastonit to 30.
you will have less alumina and may find a good soft bedding to these wild
horses.
Ababi Sharon
sharon@shoval.org.il
http://www.milkywayceramics.com/cgallery/asharon.htm
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