Veena Raghavan on sun 18 nov 01
Dear claybuds,
I hope that someone can help me with this problem. I made a large oval
lidded casserole for my daughter (at her request), in cone 6 white
stoneware (Highwater Buncombe), and glazed it with floating blue. It did
not look quite right to me, when it came out of the kiln, but then floati=
ng
blue does have its moods. However, when she put water in it, and this was=
several days after it came out of the kiln, the glaze crazed. I have not
had this happen to me with floating blue on stoneware of porcelain at con=
e
6 (all midfire clays), nor have I had this happen with this clay. I have =
a
feeling it was underfired.
My question: if I brush a thin layer of glaze on it and refire it to a tr=
ue
cone 6, would this eliminate the problem and vitrify the clay. I am
assuming that the kiln was underfired and that the clay did not vitrify.
Would this assumption be correct. As I do not do the firing myself as yet=
,
I and since this was in the middle of the holiday sale preparation rush, =
I
am not even sure who fired the kiln, so cannot get any information about
the firing.
Any help or advice would be appreciated. Thank you in advance.
All the best, and I hope everyone has a very Happy Thanksgiving.
Veena
Veena Raghavan
75124.2520@compuserve.com
Snail Scott on sun 18 nov 01
At 03:24 AM 11/18/01 -0500, you wrote:
>...filled with water
>several days after it came out of the kiln...the glaze crazed...
>My question: if I brush a thin layer of glaze on it and refire it to a true
>cone 6, would this eliminate the problem and vitrify the clay...
I think it's worth a try. Be careful, though! If it was
undervitrified, some water will have absorbed into the clay,
and the glaze will prevent it from escaping. Heat it slowly
for a long time, maybe in the oven on the lowest setting
with the door cracked, for a day or so, or candle the kiln
or a very extended time, to dry it out before firing. Or
put it on top of (or near) the kiln during your next few
firings. Anyway, dry it slowly!
-Snail
Cindy Strnad on sun 18 nov 01
Dear Veena,
A number of things could have caused your usually
reliable glaze to craze. I don't know if
underfiring is one of them. Might be, as you
mention that your glaze also had a different
visual appearance. It could also be that you got
the glaze on thicker than usual. Just a quick
eye-ball test to see if the clay is vitrified:
splash some water droplets on an unglazed portion
of the casserole. If it soaks in, it's *really*
underfired. Splash some water on the bottom of a
piece you know to be vitrified and note if there's
any difference in the behavior of the water. This
may or may not help--it depends on just how
underfired the casserole might be--but it's easy
and therefore worth a try.
Unless you know that your glaze was applied too
thinly, I think I'd skip applying another coat.
It's my experience that the bottoms of bowls,
casseroles, etc., tend to get a thicker coat than
the rest of the pieces anyhow. I don't use
Floating Blue and so I don't know how it reacts to
a second firing. But if you want to do this, just
place the clean, dry piece in the kiln as it is.
Be sure the entire firing, and especially the
original heating up, goes very slowly. I know this
is difficult as you're not personally controlling
the firing, but it's very important. If you fire a
glazed piece too quickly, you will often end up
with pieces of your glazed piece stuck to every
other pot in the kiln. Refiring will get rid of
the crazing--for a while. If the fit is bad or the
glaze too thick, the piece will craze all over
again. But this should fix your problem if it's
due to underfiring, and if the glaze can tolerate
a second firing.
Best of luck,
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com
Lorraine Pierce on sun 18 nov 01
Hi Veena...First I will say that I like Highwater clays, however, when I was
testing different ^6 commercial bodies, and Buncombe, ^3-^6 was mentioned,
my supplier said, "Oh, you don't want that for your ^6 functional
ware...thats earthenware". So I never tested it with my ^6 glazes. I assumed
he had experience I did not. Not very enlightening, but
perhaps when your answers all come in, it will help the overall picture.
Lori in New Port Richey, Fl.
Christena Schafale on mon 19 nov 01
Veena,
I don't know what will happen if you refire the casserole, though I can say
that I have had very limited success with refiring Floating Blue (tends to
change color in unattractive ways and/or to blister). I also have had a
lot of crazing on Buncombe White with glazes that don't seem to craze on
other clays, so, if you haven't been using this clay/glaze combo before, I
might be apt to attribute it to the clay.
Chris
>I hope that someone can help me with this problem. I made a large oval
>lidded casserole for my daughter (at her request), in cone 6 white
>stoneware (Highwater Buncombe), and glazed it with floating blue. It did
>not look quite right to me, when it came out of the kiln, but then floating
>blue does have its moods. However, when she put water in it, and this was
>several days after it came out of the kiln, the glaze crazed. I have not
>had this happen to me with floating blue on stoneware of porcelain at cone
>6 (all midfire clays), nor have I had this happen with this clay. I have a
>feeling it was underfired.
>
Consultation and Referral Specialist
Resources for Seniors
christenas@rfsnc.org
www.resourcesforseniors.com
Phone: (919) 713-1537
FAX: (919) 872-9574
1110 Navaho Dr, Suite 400
Raleigh, NC 27609
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