Dawn Raburn on fri 9 mar 07
Regarding a revision of Marty's Butterscotch cone 6.
The recipe is as follows;
3134 25
dolomite 12
lithium 2
g200 10
om4 26
silica 9
rutile 4
titanium diox 9
It is getting thick and crawling. Is there any fix or do I just need
to toss it? It is a nice color but a pain to apply.
Dawn
June Perry on sat 10 mar 07
That glaze is low in silica and a bit low in alumina for a cone 6 glaze. I
reformulated to bring up the silica and alumina, close to the recommended
cone 6 limit. I used some frit 3195 to satisfy some of the boron. It also
supplies more alumina than 3134, so that enabled me to lower your clay content
which should stop the crawling.
I pretty much kept the RO column the same, just altering the alumina and
silica.
I also used spodumene to get the lithium, which is a better choice than
using pure lithium carbonate. It also contributes a little alumina to the mix
which helped to lower the high clay content.
This version has a much lower expansion rate, so it will be less apt to
craze. The original has a high expansion rate.
I'm also enclosing another version with the original silica alumina but
altering the clay content as in the first revision. I'm doing that so you will
have a comparison to see if the color is altered greatly with the extra silica.
In reduction yellows too much silica is not desirable for good iron yellows.
It tends to dull/dirty the color or give it a mustard look instead of a nice
yellow.
I also brought the recipe up to 100% and of course, had to change the
percentage of oxides in relation to that, since in the original they were part of
the formula which was less than 100%. I also added a little bit of iron to
make up for what we lost by lowering the #OM4 ball clay.
June's c6 butterscotch revised #1(almost the minimum cone 6 silica limits
for silica,etc.)
7.2 Frit 3134
12 dolomite
12.6 OM #4 Ball Clay
19.1 G-200 Feldspar
18.3 silica
17.2 frit 3195
2.9 Whiting
10.7 spodumene
-------
100 Total
ADD: rutile 4.82%
titanium dioxide 10.84%
red iron oxide 0.41%
June's c6 Butterscotch revision #2 matching original but lowering clay and
getting other materials to supply the alumina and silica. There is a slight
different in the proportion of the potassium and sodium but the total Kna isthe
same. You'll notice that the titanium is higher. We lost some when we lowered
the ball clay, so I upped the titanium addition to make up for it. As in the
first revision, the RO column is the same; but in this one the silica and
alumina are as the original.
You'll also notice a slight addition of red iron oxide, as in the first
revision. That makes up for the iron we lost by lowering the OM #4 ball clay.
This version still has a high expansion rate which will probably cause crazing
if not immediately, then down the line.
21.51 Frit 3134
15.14 dolomite
12.32 OM #4 Ball Clay
17.15 G-200 Feldspar
10.50 silica
9.30 frit 3195
1.28 Whiting
12.70 spodumene
========
100 TOTAL
ADD: rutile 4.82%
titanium dioxide 11.39%
red iron oxide 0.41%
You might also try combing these two in equal parts as a third testing
option.
Let me know how they work.
Regards,
June
http://shambhalapottery.blogspot.com/
http://www.angelfire.com/art2/shambhalapottery
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Timothy Joko-Veltman on sat 10 mar 07
Dawn,
I could very easily be wrong, but my first impression is that this
glaze is really heavy on the ball clay - and hence sticks really
easily to the pot, giving an over thick layer that likes to crawl.
My first suggestion might be to try adding a little more water to the
glaze slurry. If that doesn't work, then maybe try switching out the
OM#4 for 19.4 EPK and +5.5 Quartz (so that Quartz totals 14.5).
Kaolin helps raw glaze adhere to the pot, too, but doesn't work quite
as well as ball clay, so it will be harder to apply really thick.
Some options - I hope they help. Let us know how it goes.
Regards,
Tim
On 3/9/07, Dawn Raburn wrote:
> Regarding a revision of Marty's Butterscotch cone 6.
>
> The recipe is as follows;
>
> 3134 25
> dolomite 12
> lithium 2
> g200 10
> om4 26
> silica 9
> rutile 4
> titanium diox 9
>
> It is getting thick and crawling. Is there any fix or do I just need
> to toss it? It is a nice color but a pain to apply.
>
> Dawn
>
> ______________________________________________________________________________
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