Ron & Nancy Hughes on fri 10 sep 04
Hi,
I was just wondering if this has happened to anyone else or any one =
knows the cause of it.=20
I have a small gallery and I was dusting it the other day, ( a =
rarity in it's self) and I found a small pit fire vase that had =
started descenagrating. Now it was bisqued before put in a pit fire. I =
have no idea how old it is ( 2 to 5 years maybe). I cover all my pieces =
with tile wax after they are washed. I put this display up last year in =
December and the vase was solid ( or I thought it was). The surface has =
deep flaking going on and the vase it's self has cracked apart. It =
looks a lot like drywall that has been water damaged. My other pieces =
are intact and looking good. I haven't a clue. I just can't imagine as =
I have other pieces that sit in the rain and the heat that have gone =
through the same process and are in good enough shape to use as shards =
for raku to sit in the kiln.
Just curious??? any one have a clue?
Thanks Nance
Barbara Lewis on fri 10 sep 04
Nance: If you did any salting of the work, such as with copper sulfate,
prior to the pit firing, that could account for the disintegration of the pot. I
had a situation with some saggar fired work where the piece was in contact
with the salt during the firing, as opposed to being fumed by the salt during the
firing. Just an idea. Barbara
Kim Lindaberry on fri 10 sep 04
Nance,
Since this piece was pit fired I can't but help wonder if the clay body
became completely vitrified or if it was still somewhat porous? If it
is still porous and it is out in the elements, going through freeze and
thaw cycles it may have become eroded. Did this pot go through
freeze/thaw cycles? That's all I can think or, other than maybe there
were bits of plaster in the clay body causing lime pops. Sometimes lime
pops happen months after a piece comes out of a firing.
Kim
On Sep 10, 2004, at 10:48 AM, Ron & Nancy Hughes wrote:
> Hi,
> I was just wondering if this has happened to anyone else or any
> one knows the cause of it.
> I have a small gallery and I was dusting it the other day, ( a
> rarity in it's self) and I found a small pit fire vase that had
> started descenagrating. Now it was bisqued before put in a pit fire. I
> have no idea how old it is ( 2 to 5 years maybe). I cover all my
> pieces with tile wax after they are washed. I put this display up last
> year in December and the vase was solid ( or I thought it was). The
> surface has deep flaking going on and the vase it's self has cracked
> apart. It looks a lot like drywall that has been water damaged. My
> other pieces are intact and looking good. I haven't a clue. I just
> can't imagine as I have other pieces that sit in the rain and the heat
> that have gone through the same process and are in good enough shape
> to use as shards for raku to sit in the kiln.
> Just curious??? any one have a clue?
> Thanks Nance
>
> _______________________________________________________________________
> _______
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
At least you're not a tail wheel. . .
Ron & Nancy Hughes on fri 10 sep 04
mmm Thanks Barbara, Bonnie H. wrote off line and said something similar. I
use lots of salt and cobalt sulfate in my pit firings. but I have never had
this happen. It makes me concerned for the many I have sold. I wonder why
just this one vase? and armed with info about the salts I am wondering
about the evaporative cooling in the gallery adding moisture to the
salts??
And is this to be expected from more pots down the road? I have been doing
pit fires for about 8 years. This is a first.
Thanks
Nance
Ron & Nancy Hughes on fri 10 sep 04
Kim,
I live in Tucson, Arizona....nope not to many freezes.
It was bisque to 05. I am no longer sure of the clay body as I have done
some searching in that area. I am just wondering if there is a test to see
if it happens or is going to happen to others. I cover them in a wax that
more or less water proof's them , although I do not use water in them and do
recommend against buyers using it as a water vessel.
If it is caused by salt as suggested, it seems it would happen to all of
them.
More and more ????'s
Nance
Ivor and Olive Lewis on sat 11 sep 04
Dear Nance Hughes,
Sound to me as though this piece might have cooled very fast after the
pit firing and that delayed action of the Beta to Alpha Quartz phase
change is doing the damage----- Best regards,
Ivor Lewis.
Redhill,
S. Australia.
Barbara Lewis on sat 11 sep 04
Hi: I have done many saggar fired pieces and this "spalling" type reaction
only happened to a couple, and it was those pieces that I experimented with by
painting the pieces with a diluted solution of copper and iron sulphates. So,
it was in my case that the salts were responsible. But I think in these
uncontrolled environments such as pit firing/saggar firing, it may be that only a
few are affected. Barbara
Bonnie Staffel on sat 11 sep 04
Dear Nance,
I also have pit fired my work using rock salt right next to my pots as well
as copper sulfate completely covering the pot. I have not experienced any
disintegration of the surfaces for several years. I have two of mine that I
particularly liked in my bathroom. With the changing climate in that room,
I have seen no change in the surface. I did not use any terra sig on these
pots either. I have not had mine outside in the winter but will make that
test this year on a waster pot. The colors and markings are remarkable,
IMO. In fact, the "color scheme" used in my new apartment was based on my
pit fired work, from plum/eggplant, putty, to copper red. Check out the
pitcher on Page 2 Recent Works on my web site for the colors.
Anyway, a friend of mine applies terra sig on all of his pots, uses the same
copper sulfate and salt, but after putting one of his pots outside over a
period of time, the surface started to disintegrate. He attributed it to
the salt. IMO I think there were other factors playing here. It could be
the clay used did not fit with the terra sig, or the terra sig was put on
too thickly. Also the changes in the weather, perhaps not being properly
waterproofed, got damp and then froze in the winter weather. At any rate,
he stopped using the salt. I recall that he was going through some clay
body testing from various sources. His pots do not have the problem any
more but he is using a new waterproofer. It is hard to pinpoint the source
of a problem when various factors are tested all at once.
I continue to use salt as I like the effects I get from the fire. I feel
that my bathroom test is good as I seal the clay with an excellent
waterproofing material. Never put much value on Future Floor polish, but
for a while it was the only thing I had available.
Warm regards,
Bonnie Staffel
http://webpages.charter.net/bstaffel
http://www.vasefinder.com/
Potters Council member
Marc Hudson on thu 16 sep 04
Hi Nance,
Sounds like you might have contimation in that pot by something that swel=
ls,=20
like plaster from an aging wedging table. When small particles of plaste=
r=20
are inadvertantly become wedged into a clay body and fired, the plaster=20
looses its chemical water and becomes anhydrous. The plaster will soak u=
p=20
any moisture, even humidity in the air, to rehydrate, thus swelling and=20
exerting enough pressure from inside the clay pot to cause spalling and/o=
r=20
flaking. There is oftem a small white, visually noticeable speck of plas=
ter=20
lacated at the deepest point of the "crater" left in the side of the pot.=
=20
Marc Hudson
Playing with Fire
Espa=F1ola, NM, USA
www.artfulnm.org/hudson.html
---------- Original Message -----------
From: Ron & Nancy Hughes
To: CLAYART@LSV.CERAMICS.ORG
Sent: Fri, 10 Sep 2004 08:48:07 -0700
Subject: descenagrating vase
> Hi,
> I was just wondering if this has happened to anyone else or any=20
> one knows the cause of it. I have a small gallery and I was=20
> dusting it the other day, ( a rarity in it's self) and I found a=20
> small pit fire vase that had started descenagrating. Now it was=20
> bisqued before put in a pit fire. I have no idea how old it is ( 2=20
> to 5 years maybe). I cover all my pieces with tile wax after they=20
> are washed. I put this display up last year in December and the vase=20
> was solid ( or I thought it was). The surface has deep flaking=20
> going on and the vase it's self has cracked apart. It looks a lot=20
> like drywall that has been water damaged. My other pieces are intact=20
> and looking good. I haven't a clue. I just can't imagine as I have=20
> other pieces that sit in the rain and the heat that have gone=20
> through the same process and are in good enough shape to use as=20
> shards for raku to sit in the kiln. Just curious??? any one have=20
> a clue? Thanks Nance
>=20
>=20
_________________________________________________________________________=
_____
> Send postings to clayart@lsv.ceramics.org
>=20
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>=20
> Moderator of the list is Mel Jacobson who may be reached at=20
melpots@pclink.com.
------- End of Original Message -------
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