Lynne Stone on thu 4 nov 99
I'm just joining the list so this subject may have already come up. I'm
currently using a cone 6 clay "with specks" (of manganese) fired in an
electric kiln. When I have reclaimed the scraps and pugged them for
reuse, the clay is much darker and when the thrown pots are dry they have
a brown stain on the surface which burns out in the bisque firing. (I
have a handy dandy vent system so I'm not concerned about fumes.) My
throwing water makes a black ring around the bucket when it sits for a
while. Apparently there is real concern about the toxic possibilities of
manganese in the raw state so I'm wondering if it is wise to recycle and
throw this clay since it seems the manganese is becoming more mixed into
the clay body instead of remaining in granular form. Anybody who knows
and cares to comment?
Lynne
Chris Schafale on fri 5 nov 99
I'll be interested to hear what others say about this, since I use
manganese-speckled clay as well. I have not observed the clay
body as whole getting darker with age or recycling (and I recycle
a lot). But it occurs to me that if the "brown stain" on the pots
burns out in the bisque firing, it's probably not due to manganese in
the clay, since that would certainly not burn out at cone 6. I've
had brown surface discoloration on some pots that did not burn out,
however, and it was suggested by folks here that this was due to
soluble salts/iron compounds coming to the surface in drying.
Chris
> ----------------------------Original message----------------------------
> I'm just joining the list so this subject may have already come up. I'm
> currently using a cone 6 clay "with specks" (of manganese) fired in an
> electric kiln. When I have reclaimed the scraps and pugged them for
> reuse, the clay is much darker and when the thrown pots are dry they have
> a brown stain on the surface which burns out in the bisque firing. (I
> have a handy dandy vent system so I'm not concerned about fumes.) My
> throwing water makes a black ring around the bucket when it sits for a
> while. Apparently there is real concern about the toxic possibilities of
> manganese in the raw state so I'm wondering if it is wise to recycle and
> throw this clay since it seems the manganese is becoming more mixed into
> the clay body instead of remaining in granular form. Anybody who knows
> and cares to comment?
> Lynne
>
>
Light One Candle Pottery
Fuquay-Varina, NC
candle@intrex.net
David Hendley on fri 5 nov 99
Lynne, I'll not comment on wisdom of using a clay that
contains granular manganese.
There has been lots of discussion about that here on
Clayart in years past. (Access the archives!)
>From your description, I think that your clay must contain
some soluble salts, and that, not the manganese, is
what is responsible for the 'brown stain on the surface
which burns out in the bisque firing', and the 'black ring
around the bucket' of your throwing water.
As long as this causes no problems with applying glazes
or the look of the finished piece, don't worry about
the brown stain or the black ring.
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: Lynne Stone
To:
Sent: Thursday, November 04, 1999 11:17 AM
Subject: Manganese in Cone 6 clay
| ----------------------------Original message----------------------------
| I'm just joining the list so this subject may have already come up. I'm
| currently using a cone 6 clay "with specks" (of manganese) fired in an
| electric kiln. When I have reclaimed the scraps and pugged them for
| reuse, the clay is much darker and when the thrown pots are dry they have
| a brown stain on the surface which burns out in the bisque firing. (I
| have a handy dandy vent system so I'm not concerned about fumes.) My
| throwing water makes a black ring around the bucket when it sits for a
| while. Apparently there is real concern about the toxic possibilities of
| manganese in the raw state so I'm wondering if it is wise to recycle and
| throw this clay since it seems the manganese is becoming more mixed into
| the clay body instead of remaining in granular form. Anybody who knows
| and cares to comment?
| Lynne
|
| |
|
