John Britt on tue 7 aug 07
Hi Ron,
I know we have had a discussion about =93black coring=94 but not about this.=
My objection is to the two terms you use: =93should=94 be =93evenly reduced=94=
.
The laminated explanation doesn=92t hold up because the same =93lamination=94=
problem would be present in your example. You say: =93If there is iron
present then the body should be the same grey or black all the way through
with a thin skin of reoxidized clay if the body is properly vitrified so
as not to leak.=94
So you can have a thin skin of reoxidized clay and that doesn=92t cause
the =93lamination=94 problems you are referring to?
Secondly, if this were the case you would think that you would see more
evidence of severe =93lamination=94 problems.
Also, it seems to me that it is almost impossible to achieve =93evenly
reduced=94 in every firing, in every spot in the kiln. So almost no one
has =93evenly reduced=94 bodies. (Unless, of course, you define =93evenly
reduce=94 very loosely. But I doubt that because you are being very specific=
about what is right and wrong.)
I don=92t think that a clay body =93should=94 be anything. It depends on wha=
t
you are trying to do. If you are firing for celadons, shinos or iron
spotting, etc. then reduce early and try to keep it consistent. I am not
against that!
But is it possible?
If you are firing for kaki=92s, oil spots, rutile blues, then oxidize and
reduce later (cone 9- 11). If you do this on a higher iron body this will
darken the iron on the surface and leave the interior light. This means
that when you break it open, it will be lighter inside and the top 1mm
will be darker. I cannot see that this is a problem. I have never
had =93lamination=94 problems. This is a way to have strong bodies that appe=
ar
to be reduced early.
Maybe I am being overly sensitive but I object to blanket statements about
what is right and wrong. There are many ways and reasons. And there is a
relatively wide range for =93error=94 in ceramics.
Another example I object to is where you say: =93If it is not then you need
to adjust your firing to make sure the clay is properly reduced before the
glazes seal over. The fault I see most often is reoxidized clay due to
slipping out of reduction before the clay is vitrified - usually where
there is no glaze.=94
I have a problem with the term =93properly reduced=94. What is the definitio=
n
of this term? And how is it achieved? Should it be heavily reduced,
lightly reduced or somewhere in the middle?
Thanks,
John Britt
www.johnbrittpottery.com
Ron Roy on thu 9 aug 07
Hi John,
No, the lamination due to the reoxidation happens only where there is no
glaze and it is too thin to be of concern.
There may be some kilns that will never fire evenly I'm sure - but I think
most can be made to fire and reduce evenly. The laminations are the clues
about how to cure the problems.
I'm not trying to imply it is easy with all kilns and it may be that some
potters will not want to fire slow enough to cure the faults.
I do know that if the clay under the glaze - in reduction - is not reduced
properly the potter is not happy.
To get even reduction is, or should be, the aim for every reduction firing
in order to get the most number of succesful pots.
If some of the clay in a pot is oxidized and some reduced - and there is
iron present - then the reduced clay will be vitrified more - surely you
can see that is not the best situation?
I think of reduction as either reduced or not. If the clay is semi reduced
I think of it as unevenly reduced.
RR
>I know we have had a discussion about =93black coring=94 but not about this=
.
>
>My objection is to the two terms you use: =93should=94 be =93evenly reduced=
=94.
>
>The laminated explanation doesn=92t hold up because the same =93lamination=
=94
>problem would be present in your example. You say: =93If there is iron
>present then the body should be the same grey or black all the way through
>with a thin skin of reoxidized clay if the body is properly vitrified so
>as not to leak.=94
>
>So you can have a thin skin of reoxidized clay and that doesn=92t cause
>the =93lamination=94 problems you are referring to?
>
>Secondly, if this were the case you would think that you would see more
>evidence of severe =93lamination=94 problems.
>
>Also, it seems to me that it is almost impossible to achieve =93evenly
>reduced=94 in every firing, in every spot in the kiln. So almost no one
>has =93evenly reduced=94 bodies. (Unless, of course, you define =93evenly
>reduce=94 very loosely. But I doubt that because you are being very specifi=
c
>about what is right and wrong.)
>
>I don=92t think that a clay body =93should=94 be anything. It depends on wh=
at
>you are trying to do. If you are firing for celadons, shinos or iron
>spotting, etc. then reduce early and try to keep it consistent. I am not
>against that!
>
>But is it possible?
>
>If you are firing for kaki=92s, oil spots, rutile blues, then oxidize and
>reduce later (cone 9- 11). If you do this on a higher iron body this will
>darken the iron on the surface and leave the interior light. This means
>that when you break it open, it will be lighter inside and the top 1mm
>will be darker. I cannot see that this is a problem. I have never
>had =93lamination=94 problems. This is a way to have strong bodies that app=
ear
>to be reduced early.
>
>Maybe I am being overly sensitive but I object to blanket statements about
>what is right and wrong. There are many ways and reasons. And there is a
>relatively wide range for =93error=94 in ceramics.
>
>Another example I object to is where you say: =93If it is not then you need
>to adjust your firing to make sure the clay is properly reduced before the
>glazes seal over. The fault I see most often is reoxidized clay due to
>slipping out of reduction before the clay is vitrified - usually where
>there is no glaze.=94
>
>I have a problem with the term =93properly reduced=94. What is the definiti=
on
>of this term? And how is it achieved? Should it be heavily reduced,
>lightly reduced or somewhere in the middle?
>
>
>Thanks,
>
>
>John Britt
>www.johnbrittpottery.com
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
| |
|
