Ron Roy on fri 26 aug 05
maturation temp)
Hi Ben,
Some glaze programs allow you to include the Fe2O3 (It's FeO after being
reduced) as a flux - that should give you a better picture of what to do.
As you do more experiments you will get a feel for just how accurate that
technique is.
If you are using Insight there is a "reduction" button that include iron in
with the fluxes.
RR
>I have done some experiments with iron and rutile and titanium in glazes at
>cone 10 reduction. I have added these to clear or white "base" glazes just
>to see what they look like. I have a result that I like the color of with
>about 4% ea of iron and rutile.
>
>The only problem is that the glaze seems over fired at ^10. I wondered if
>there is a general way to calculate the fluxing effects of iron at this temp
>or just some general guidelines for raising the matuation temp of a glaze.
>
>Logic would point me towards increasing the silica and alumina in relation
>to the fluxes (or lowering the flux content) BUT the other day I was reading
>up on Eutectic effects. WHOOOOOOAAA that throws a monkey wrench into it.
>
>If I had the glaze recipe with me, I'd post it. I'll have to do that later
>but for now, is there any general info that might benefit my understanding
>of why a white, non-gloss glaze would be overfired when adding 4% iron and
>rutile?
>
>Thanks
>
>Ben
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on fri 26 aug 05
maturation temp)
Hi Ben,
The problem with adding kaolin - you will upset the ratio of the glaze -
unless the ratio of the kaolin matches that of the glaze.
The ratio of silica to alumina in EPK is about 2 - much lower than any
pottery glaze we use.
A better way is to reduce the amount of one of the fluxes - depending on
what you want to happen to the expansion of the glaze.
I find glaze and clay calculation to be rather accurate most of the time -
paying attention to the material definitions is a must of course.
RR
>I'll be using Glaze master if ever I get my "shop" computer up and running.
>I don't know if it has this feature or not.
>Lee Love's suggestions from Leach is add 0.5% Kaolin for every 1% of added RIO.
>
>This should be enough for a nice test. I never really expect calculations to
>be 100% accurate when tested out. They do provide a great place to start for
>a test of this nature. I am sure that I will have to run a series of tests
>with added kaolin above and below the calculated value. Now I have abetter
>idea of a point to start from and a feel for what size increments to use for
>the tests.
>
>Thanks
>
>Ben
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Tom at Hutchtel.net on sun 28 aug 05
maturation temp)
> include iron in flux unity. You can toggle between alumina unity
> (sometimes used in clay body calculations) and iron in flux unity.
>
Hi John,
Talk to me a bit more about how using an alumina unity works in formulating
a clay body.. Are there limit guidelines, and if so, where are these found.
I understand that you can't really use calculation software for clay bodies,
other than directionally, but how can it be legitimately used to assist in
clay body work? Ron or others, chime in if you would
Tom Wirt
Hutchinson, MN
twirt@hutchtel.net
www.claycoyote.com
Ron Roy on wed 31 aug 05
maturation temp)
Hi Bruce,
As you begin to make comparisons - particularly with clays and glazes that
you have information about - you can see the numbers and compare them.
For instance - say you know the absorbency of a white clay body and you
calculate it - you will see the amount of alumina and silica. That gives
you the clue you need to get some idea of how much is needed in a dark clay
- with Fe2O3 in it. If you want to fire it in oxidation you leave the iron
out of the unity flux group - if you are firing in reduction put it in with
the fluxes - just get the amount of alumina right for each situation and
you have an excellent starting point.
When you do include it with the fluxes you will see the amount of alumina
and silica will be less.
It is always so when calculating the Seger formula - add flux and the other
oxides go down - which is like saying they will melt at a lower
temperature.
If you find your absorbency is to low - increase the alumina and silica -
if to open reduce the alumina and silica - or add flux
I am very fortunate in all this because I have clay body test results going
back 20 years - I make changes to clay bodies for a number of reasons
constantly - and all I am doing is comparing recipes and molecular
formulas. It works like a charm - when a clay is no longer available I can
usually insert a new clay and get the absorbency right the first time.
I'm pretty sure this is not enough to answer your question - so let me know
if you need more. If you want to send an example of a clay body - or a
glaze perhaps I can show you an example of how I do it.
>Ron Roy wrote:
>>Some glaze programs allow you to include the Fe2O3 (It's FeO after being
>>reduced) as a flux - that should give you a better picture of what to do.
>
>>If you are using Insight there is a "reduction" button that include iron in
>>with the fluxes.
>
>But how does that tell you anything about the melt temperature? I can
>compare my unity formula with published limits, but how do we get from
>clicking the "reduction" checkbox in Insight to something like "adding 1%
>RIO will drop my maturation temperature by 20 degrees"?
>
>Is there any way at all to predict a maturation temperature using any of the
>glaze calc programs?
>
>Bruce "babes in the forest" Girrell
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
Ron Roy on wed 31 aug 05
maturation temp)
Hi Tom,
I do use calculation for clay bodies - constantly - see my post to Bruce.
I'm sure my answer will lead to other questions and I will try to explain.
For instance - If you calculate the classic c10 porcelain and replace the
g200 with Neph Sy to bring it down to cone 6 - you will have a good model
to develop other porcelains for cone 6, cone 8 and cone 10 - once you know
that you can more easily proceed to even higher temperatures.
Classic cone 10 porc.
25 G200
25 Ball clay (OM#4) for instance
25 Porcelain (EPK)
25 Silica
If you calculate that out - using different ball clays and kaolins for
instance you will soon see a range of the amount of Al2O3 and SiO2. Once
you have tested a few you can really start to see what is needed and how to
get what you want.
The beauty of the Seger unity is - if the fluxes all total 1 then you can
compare alumina and silica to "see" what cone it fires at and how to move
temperature up and down.
I use the flux unity for bodies by the way - I do take a look at them using
alumina unity - it is usable either way I suppose - I just find the flux
unity works fine for me.
There is some confusion about alumina unity I think - when entering clays
in a material table - when computers were slow - the molecular weight of a
clay when - entered with unity on the fluxed - was very large - and slowed
the already slow results even further. With current speeds I don't think it
makes much of a difference.
Many of the clays in my MDT are entered with unity on the fluxes.
There are some who only use mol percent - or even percent when working on
clays and glazes - it's what you get used to.
I got used to working with unity on fluxes and it was easy for me to simply
keep doing it that way when I started working on bodies.
RR
>> include iron in flux unity. You can toggle between alumina unity
>> (sometimes used in clay body calculations) and iron in flux unity.
>>
>
>
>Hi John,
>
>Talk to me a bit more about how using an alumina unity works in formulating
>a clay body.. Are there limit guidelines, and if so, where are these found.
>
>I understand that you can't really use calculation software for clay bodies,
>other than directionally, but how can it be legitimately used to assist in
>clay body work? Ron or others, chime in if you would
>
>Tom Wirt
>Hutchinson, MN
>twirt@hutchtel.net
>www.claycoyote.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
| |
|
