David & Diane Chen on tue 10 aug 99
------------------
In spending my typical hour with coffee and archives a few days ago, I came
across this glaze called 69 Green (cone 5) that Paul Lewing provided and
indicated it would break. Well I tried it and break it did. Very =
interesting,
but I am confused. In my limited experience, I couldn't understand which of=
the
glaze ingredients provided the magic =22break=22. The glaze ingredients =
are:
Neph Sye 50
Whiting 20
Frit 3134 20
Ball Clay 10
Rutile 5
Copper Carb 2
I am using this on non-functional ware, but still would like to understand =
the
=22why=22 of the breaking glaze. I thought it was mainly titanium and =
lithium(?)
that provided this ability.
Can anyone enlighten me?
Diane
in Massachusetts where the dogs on their walk this morning wanted to chase =
down
the two deer we spotted. Since the dogs have the ability to fell the deer, =
(and
both out-weigh their owner) it is no small feat that their objective was
thwarted=21
Mike Bailey on wed 11 aug 99
In message , David & Diane Chen writes
Dear Diane,
Have a look at the names of the molecules that make up the mineral
rutile - it's really titanium dioxide plus a bit of iron and, as you
say, it's the TiO2 that gives a break to the glaze.
The other factor which is a bit more complicated is the alumina:silica
balance - There are certain limits in which the break will either show
up well or will barely be apparent. For example, if you had a high
alumina matt glaze the addition of rutile/titanium wouldn't give much
evidence of a 'break'.
Obviously the glaze you mention has an alumina:silica balance that gives
you a base glaze that works well for this effect.
Cheers,
Mike.
>----------------------------Original message----------------------------
>------------------
>
>Diane
>in Massachusetts where the dogs on their walk this morning wanted to chase =
>down
>the two deer we spotted. Since the dogs have the ability to fell the deer, =
>(and
>both out-weigh their owner) it is no small feat that their objective was
>thwarted=21
>
--
Mike Bailey
Dwiggins, Sandra (NCI) on wed 11 aug 99
In my experience of glaze chemistry (limited, though), it's usually the Rutile.
Sandy
Sandra Dwiggins
Sandra Dwiggins
Technical Information Specialist
Office of Cancer Information, Communication and Education
National Cancer Institute
National Institutes of Health
e-mail: sdwiggin@exchange.nih.gov
fax:301-480-8105
phone: 301-496-7406
-----Original Message-----
From: David & Diane Chen [SMTP:parishrd@netway.com]
Sent: Tuesday, August 10, 1999 2:01 PM
To: CLAYART@LSV.UKY.EDU
Subject: green break from Paul Lewing
----------------------------Original message----------------------------
------------------
In spending my typical hour with coffee and archives a few days ago, I came
across this glaze called 69 Green (cone 5) that Paul Lewing provided and
indicated it would break. Well I tried it and break it did. Very interesting,
but I am confused. In my limited experience, I couldn't understand which of the
glaze ingredients provided the magic "break". The glaze ingredients are:
Neph Sye 50
Whiting 20
Frit 3134 20
Ball Clay 10
Rutile 5
Copper Carb 2
I am using this on non-functional ware, but still would like to understand the
"why" of the breaking glaze. I thought it was mainly titanium and lithium(?)
that provided this ability.
Can anyone enlighten me?
Diane
in Massachusetts where the dogs on their walk this morning wanted to chase down
the two deer we spotted. Since the dogs have the ability to fell the deer, (and
both out-weigh their owner) it is no small feat that their objective was
thwarted!
Kris Griffith on wed 11 aug 99
Glazes with rutile are usually "breakers" At least that is my experience,
however their are those more knowledgeable on this list that could tell you
why that was.
Kris
-----Original Message-----
From: David & Diane Chen
To: CLAYART@LSV.UKY.EDU
Date: Tuesday, August 10, 1999 1:33 PM
Subject: green break from Paul Lewing
----------------------------Original message----------------------------
------------------
In spending my typical hour with coffee and archives a few days ago, I came
across this glaze called 69 Green (cone 5) that Paul Lewing provided and
indicated it would break. Well I tried it and break it did. Very
interesting,
but I am confused. In my limited experience, I couldn't understand which of
the
glaze ingredients provided the magic "break". The glaze ingredients are:
Neph Sye 50
Whiting 20
Frit 3134 20
Ball Clay 10
Rutile 5
Copper Carb 2
I am using this on non-functional ware, but still would like to understand
the
"why" of the breaking glaze. I thought it was mainly titanium and
lithium(?)
that provided this ability.
Can anyone enlighten me?
Diane
in Massachusetts where the dogs on their walk this morning wanted to chase
down
the two deer we spotted. Since the dogs have the ability to fell the deer,
(and
both out-weigh their owner) it is no small feat that their objective was
thwarted!
Paul Lewing on wed 11 aug 99
David & Diane Chen wrote:
>
> ----------------------------Original message----------------------------
> ------------------
> In spending my typical hour with coffee and archives a few days ago, I came
> across this glaze called 69 Green (cone 5) that Paul Lewing provided and
> indicated it would break. Well I tried it and break it did. Very interesting
> but I am confused. In my limited experience, I couldn't understand which of t
> glaze ingredients provided the magic "break". The glaze ingredients are:
>
> Neph Sye 50
> Whiting 20
> Frit 3134 20
> Ball Clay 10
> Rutile 5
> Copper Carb 2
>
> I am using this on non-functional ware, but still would like to understand the
> "why" of the breaking glaze. I thought it was mainly titanium and lithium(?)
> that provided this ability.
>
> Can anyone enlighten me?
>
> Diane
Hi, Diane,
I think two things are causing this glaze to "break". One you
identified yourself. Rutile is 90+% titanium, with a little yellow iron
and other stuff.
The other is that this is a pretty unbalanced glaze. It has alumina at
the very top of the limit formula levels and the silica is way under
what limit formulas suggest. Consequently, it has a Si:Al ratio of only
a little over 5, which is pretty low.
There was a little talk of layering glazes recently. I've observed that
the most spectacular interactions betwen glazes occurs when the Si:Al
ratios of the two glazes have a difference of 7 or more. So find a
glaze with a ratio of 12 or more (low alumina/ high silica) and watch
them really produce some action.
Paul Lewing, Seattle,
tired after a great 12-mile day hike in the Alpine Lakes Wilderness
Area. Nice to be able to have breakfast at the regular time, get up
there, do the 12 miles, with 2500' elevation gain, see about six lakes
and make it home by dinner time.
David & Diane Chen on thu 12 aug 99
Okay, now Paul, for a really stupid question. You say that the Si:Al ratio
is a little over 5 which is low. What is optimum in terms of this ratio,
and what happens with a low Si:Al ratio. Is the glaze more likely to crawl,
or craze, or what?
PS, I am traveling to Seattle next week. Anything thing I should
specifically see?
Diane in a very unusual cloudy, yes cloudy, day in Massachusetts
Paul Lewing on fri 13 aug 99
David & Diane Chen wrote:
>
> ----------------------------Original message----------------------------
> Okay, now Paul, for a really stupid question. You say that the Si:Al ratio
> is a little over 5 which is low. What is optimum in terms of this ratio,
> and what happens with a low Si:Al ratio. Is the glaze more likely to crawl,
> or craze, or what?
Hi, Diane,
That's not at all a stupid question. Even if you learned how to do the
math for glaze calc in school years ago, they didn't tell you about
Si:Al ratio, so it's only people who are now familiar with glaze-calc
programs that are used to looking at this number.
This ratio is one of the main indicators in predicting what kind of
surface you're going to get, whether matt or glossy. It's not a simple
linear relationship (is it ever in ceramics?) but generally, the lower
the ratio, the more matt the glaze. The presence or absence of boron
complicates this enormously, and so does the fact that matt glazes can
be produced in other ways than low Si:Al ratios.
But it would be very rare for a glaze with a ratio below about 4.5 to be
anything other than very matt, and just as rare for a glaze with a ratio
over about 13 to not be runny. To illustrate, so-called "lichen" glazes
typically have a ratio of 2 or 3, and crystalline glazes typically have
a ratio over 50, sometimes as high as 100.
By the way, this holds true across the range of firing temperatures.
And only in a very general way does this number have anything to do with
crazing or crawling.
>
> PS, I am traveling to Seattle next week. Anything thing I should
> specifically see?
>
> Diane in a very unusual cloudy, yes cloudy, day in Massachusetts
The best thing anywhere around Seattle is Mount Rainier. I hope it's
"out" while you're here. And maybe summer will arrive by next week and
hopefully even last out the week.
Paul Lewing, Seattle
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