mel jacobson on wed 19 sep 07
just wanted to say that.
i love rutile.
i use it a great deal...it makes my pots
better and more beautiful.
l love rutile.
and, as ron has pointed out.
it does good things in its chemistry.
from: mel/minnetonka.mn.usa
website: http://www.visi.com/~melpots/
Clayart page link: http://www.visi.com/~melpots/clayart.html
Ivor and Olive Lewis on thu 20 sep 07
Dear Mel Jacobson ,
An interesting proposition but even with the support of Ron Roy,
<<...as ron has pointed out. it does good things in its chemistry..>>
...it can only do things because it does not seem to enter into any =
reactive chemistry in a vitreous silicate melt below about 1550 deg C. =
An even higher temperature is needed for it to react with Alumina.
The way we use Rutile relies its inertness. So there is not reactive or =
reconstructive chemistry. But as an insoluble substance I can see the =
point of using it as a nucleating agent. Perhaps some one might =
investigate its use as a Catalyst.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Bruce Girrell on thu 20 sep 07
Ivor Lewis wrote:
> ...it can only do things because it does not seem to enter into any
reactive chemistry in a vitreous silicate melt below about 1550 deg C.
> An even higher temperature is needed for it to react with Alumina. The way
we use Rutile relies its inertness.
> So there is not reactive or reconstructive chemistry. But as an insoluble
substance I can see the point of using it as a nucleating agent.
In my efforts to develop a rutile glaze that would create the effects that I
wanted, I have found that poorly melted rutile results in very muddy color
and that my best effects occur when the rutile has fully melted. In order to
check melting, I place drawrings in the kiln and start pulling them at ^10.
As soon as a ring cools sufficiently to handle it, I examine it with a
microscope to check the melt and I don't stop firing until I get a full
melt. At times I'm pushing ^13, but that's still well below 1550.
If the rutile melts, but is nonreactive, what is it doing? Why do you say
that it's nonreactive? I guess I'm not clear on what you mean by
nonreactive.
Bruce "always a troublemaker" Girrell
BTW, has anyone told mel that his pots might turn blue if he keeps up with
this rutile nonsense?
Ivor and Olive Lewis on fri 21 sep 07
Dear Bruce Girrell,
To answer your questions I would need more information, in a general =
way, about the composition of your recipes.
Best regards,
Ivor=20
Bruce Girrell on fri 21 sep 07
Ivor wrote: I would need more information, in a general way, about the
composition of your recipes.
Ivor,
We have achieved our most successful results using Pete Pinnel's Cash Blue
layered over Rutile Blue 51 (which I thought was David Hendley's, but found
out otherwise when I saw that David credits Big Creek Pottery). Since the
Rutile Blue 51 recipe is heavy in iron, you can't really see into it very
well. It is a dark brown at ^10.
My observations, then, are based on examination of the Cash Blue layer,
which is quite transparent at ^10. The drawrings are dipped like the pots:
RB51 first, then CB on top, though I tilt the rings first one way, then the
other as I dip them so that there is a little bit of each glaze that is
single layer. Melting in the single layer portion is no different from that
in the layered portion. Other experiments indicate that the thickness of the
RB51 is not very important, but that the CB should not be thin. Otherwise
the glaze does not flow properly and I consider flowing to be important in
achieving the effect that I like.
Cash Blue, cone 10 (from Pete Pinnell)
47.3 Nepheline Syenite
14.2 Gertsley Borate
27.5 Flint
9.3 Whiting
1.7 Zinc Oxide
+4 Rutile
#51 Rutile Blue, from Big Creek Pottery, Davenport, California, 1973
Feldspar (I've used all kinds, they all worked).....357 <-- David's
comment, not mine. I use Custer - BG
Flint.....436
Whiting.....159
Kaolin.....137
Red Iron Oxide.....50
Rutile.....50
Does that help?
Bruce
Gary Navarre on sat 22 sep 07
On Wed, 19 Sep 2007 16:04:45 -0500, mel jacobson wrote:
>just wanted to say that.
>
>i love rutile.
>i use it a great deal...it makes my pots
>better and more beautiful.
>l love rutile.
What first got me wondering what rutile would do was a brownish ^5 cup in
high school that had a bluish white squiggle of a cloud with some
iridescence in the bottom. Years later had some great results mixed with the
ash slip, especially in salt. I know it likes to be hot and have a slow cool
down soaking. Peter and Rick told me there is an outcrop of crystals a
couple miles from here up Pine Creek in the 300' pre-cambrian bluffs. If
Peter found them there probably won't be any high climbing involved. Maybe
I'll get a chance to find some to grind up and see what happens next year
when the kiln is firing hot enough.
G in da U.P.
Ivor and Olive Lewis on sun 23 sep 07
Dear Bruce Girrell,
Two complex recipes.=20
"Non Reactive".... is reluctant to enter into chemical =
reactions....Difficult to dissolve.
Titanium Dioxide is chemically unreactive and does not seem to do much =
with anything of interest. If it is melted with Silicon dioxide there is =
no chemical reaction. On cooling a mixture of these two compounds forms =
a blend of crystals of each, Rutile and Cristobalite.=20
TiO2 reacts with Iron oxide to give black Ilmenite.
In the presence of Lime, Rutile will dissolve in a silicate melt at =
temperatures above about 1250 deg C.=20
Since you are getting a transparent glaze I suggest that the Blue =
colouration is due to some form of optical effect. This is not unusual =
when you have Boron oxide in the glaze but difficult to explain =
otherwise, except where immiscibility of two fluids is involved.
Best regards,
Ivor.=20
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