Ron Roy on sun 19 aug 01
Hi again Marianne,
It does not matter at all if a glaze has iron in it - to work on a high
iron body. What is of more importance is how and if a glaze breaks on
edges. I dark body will show those edges as darker - on a light body those
edged will probably show as lighter.
Dark bodies tend to show those differences better but the real key to
getting what you want is glaze application. Thinner meams more details show
through usually.
You need to make some test tiles or ware that have some raised lines as
decoration - even throwing marks will show with some glazes - thin your
glaze out a bit and dip or pour different thicknesses.
The Mid Red has nearly 4% iron in it by the way - this information is
always available in a MSDS (Materials Safety Data Sheet) from your supplier
- just ask - it's the law.
RR
>After trying out various Tucker's clay bodies over the past year, I have
>decided to stick with their mid red stoneware. The color on the foot is
>nice (hate those naked white feet from other claybodies), unglazed areas
>on the outside of pots look great, and the clay is nice to throw.
>
>Many glazes perform differently on my Tucker's white stoneware and the
>Tucker's mid red stoneware. I guess the mid red clay body must have a
>high iron content to produce the nice red/brown color.
>
>Is there a logical way to examine glaze recipes to determine which ones
>are most likely to perform well on the mid red clay? For instance, if a
>glaze has no RIO, is it logical to guess that it won't perform well on the
>mid red clay? If it has some RIO, is it logical to perhaps reduce a
>percentage of the RIO to accommodate the iron in the clay? Or, is my
>thinking all wrong on this?
>
>I realize actual firing tests will be necessary. But since I am still
>trying to get all of these candle holders made in a short timeframe for my
>son's wedding (most of the earlier ones already done will get the hammer,
>because my throwing has improved considerably now), my "tests" are going
>to have to be on these, and hope for the best.
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
Marianne Lombardo on sun 19 aug 01
After trying out various Tucker's clay bodies over the past year, I have =
decided to stick with their mid red stoneware. The color on the foot is =
nice (hate those naked white feet from other claybodies), unglazed areas =
on the outside of pots look great, and the clay is nice to throw.
Many glazes perform differently on my Tucker's white stoneware and the =
Tucker's mid red stoneware. I guess the mid red clay body must have a =
high iron content to produce the nice red/brown color. =20
Is there a logical way to examine glaze recipes to determine which ones =
are most likely to perform well on the mid red clay? For instance, if a =
glaze has no RIO, is it logical to guess that it won't perform well on =
the mid red clay? If it has some RIO, is it logical to perhaps reduce a =
percentage of the RIO to accommodate the iron in the clay? Or, is my =
thinking all wrong on this?
I realize actual firing tests will be necessary. But since I am still =
trying to get all of these candle holders made in a short timeframe for =
my son's wedding (most of the earlier ones already done will get the =
hammer, because my throwing has improved considerably now), my "tests" =
are going to have to be on these, and hope for the best.
Marianne Lombardo
Omemee, Ontario, Canada
email: mlombardo@nexicom.net
Paul Lewing on sun 19 aug 01
on 8/19/01 12:25 PM, Marianne Lombardo at mlombardo@NEXICOM.NET wrote:
> Is there a logical way to examine glaze recipes to determine which ones =
> are most likely to perform well on the mid red clay? For instance, if a =
> glaze has no RIO, is it logical to guess that it won't perform well on =
> the mid red clay? If it has some RIO, is it logical to perhaps reduce a =
> percentage of the RIO to accommodate the iron in the clay? Or, is my =
> thinking all wrong on this?
No, there isn't a logical way to examine glaze/clay interactions as you
hope. With experience, you would probably be able to extrapolate pretty
closely, but there are just too many variables. One of the biggest is your
phrase "perform well". No one but you has any idea what that means. If you
mean will a glaze that melts to a smooth, functional surface on a white
clay also melt to a smooth surface on a red clay, the answer is "probably".
The only variable there would be that iron is a flux in reduction and
refractory in oxidation, and that will affect the vitreousness off your
clay, and hence its interaction with glazes. If you mean will it look the
same, the answer is "probably not, unless it's a very opaque glaze". If you
mean, will it be as pleasing a color, the answer is "pleasing to whom and
for what?". If you mean will it fit as well, the answer is "maybe, maybe
not". If you stick with clay long enough, you eventually realize the answer
to every question is "It depends".
I find in teaching glaze workshops or discussing glaze software with people
who've never used it, that predicting color is one of the things they most
hope it will do. Well, it doesn't. The reasons that it doesn't is that
there are too many variables, and the results are too subjective. Computers
deal in numbers, and you can't quantify color, at least not in the way that
ceramic materials generate colors.
>
> I realize actual firing tests will be necessary.
And right there you have the only answer you'll ever need.
Happy testing!
Paul Lewing, Seattle
Marianne Lombardo on mon 20 aug 01
After opening up my latest glaze firing, I now realize that even testing
doesn't seem to mean a lot. Two different pots on two different shelves in
the kiln, exact same glaze combinations on each pot and are they ever
different. Both are lovely, but in a different way. Very, very different.
Now I have to stop just putting large witness cones on the middle shelf, and
use them on all levels to determine what's going on so I can duplicate these
glaze effects. I suspect that the lower level is probably a cone lower.
Marianne Lombardo
Omemee, Ontario, Canada
email: mlombardo@nexicom.net
----- Original Message -----
From: "Paul Lewing"
Subject: Re: Red Clay & Iron & Glaze Question
> on 8/19/01 12:25 PM, Marianne Lombardo at mlombardo@NEXICOM.NET wrote:
>
> not". If you stick with clay long enough, you eventually realize the
answer
> to every question is "It depends".
> >
> > I realize actual firing tests will be necessary.
>
> And right there you have the only answer you'll ever need.
> Happy testing!
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