Firing disaster - input please

We have been having problems with our kilns but our last firing is the most
bizarre we have had to date. We fired 2 kilns starting at the same time
with the same ramping schedule. It is a modified version of MC6's posted
version (Oxidation - cone six - Skutt electric kilns).

Segment Rate Temp Hold

1 100 220 0
2 350 2000 0
3 150 2180 25
4 500 1900 0
5 125 1400 0

Both kilns had comparable pots and the same glazes. Both showed the same
cone characteristics (top shelf cone 5 flat cone six tipping and the other
shelves show cone six past middle but not quite flat). #1 kiln took 18+
hours to fire and #5 kiln took about 14+ hours. The firing unless my math is
way off should have been about 13hours.


The glazes in kiln #1 were perfect though still overfired (a little pitting
on one piece). The glazes in kiln #5 were a disaster. A large percentage
of them had severe crawling. The glazes this showed up on are floating
blue, MC6 Spearmint, MC6 Bone, Raspberry - I think that is it. The other
issue that we saw was a pot cracking as if their was a glaze fit problem but
I think this is a different issue because I have been finding people
sneaking in non-studio underglazes and clays.

So... what are the thoughts on this?

"dkat" wrote in message
...
We have been having problems with our kilns but our last firing is the
most
bizarre we have had to date. We fired 2 kilns starting at the same time
with the same ramping schedule. It is a modified version of MC6's posted
version (Oxidation - cone six - Skutt electric kilns).

Segment Rate Temp Hold

1 100 220 0
2 350 2000 0
3 150 2180 25
4 500 1900 0
5 125 1400 0

Both kilns had comparable pots and the same glazes. Both showed the same
cone characteristics (top shelf cone 5 flat cone six tipping and the
other
shelves show cone six past middle but not quite flat). #1 kiln took 18+
hours to fire and #5 kiln took about 14+ hours. The firing unless my math
is
way off should have been about 13hours.


The glazes in kiln #1 were perfect though still overfired (a little
pitting
on one piece). The glazes in kiln #5 were a disaster. A large percentage
of them had severe crawling. The glazes this showed up on are floating
blue, MC6 Spearmint, MC6 Bone, Raspberry - I think that is it. The other
issue that we saw was a pot cracking as if their was a glaze fit problem
but
I think this is a different issue because I have been finding people
sneaking in non-studio underglazes and clays.

So... what are the thoughts on this?



Crawling is usually more about dust or something on the pot before glazing.
I don't really have any answers, but maybe there were more odd underglazes
and clays there than you thought??
I found it difficult to work out your firing schedule, also I work in
centigrade. Why so complicated?
In my experience holding at different stages is not necessary usually. I
soak at top temp always for half an hour. I know when cooling periods of
soaking are necessary for crystaline glazes, but why so complicated for
these glazes?

This is the firing recommended on Mastering Cone 6 FAQ and I like it. We
are not doing the crystallized glazes (where you try to grow giant crystals)
but our glazes do form crystals which is what gives the glazes a feeling of
depth or color. Toby's red develops it's red color with slow cooling.
Floating Blue becomes opalescent. The glazes from MC6 for a satin matt
rather than a glossy clear.

Again, the two kilns had the exact same glazes, clay bodies for at least a
few of the pieces were clearly recognizable as 112, and there were problems
with pots of experienced potters that I trust to tell me if they had used
outside clay or glazes and I could recognize the clay body and glazes on
most pieces in any case. I noticed that I left out one piece of
information. The kiln that had the crawling had not come to temperature
with an Error 1 and had to be refired. There was no error with the refire
and the cones looked fine. Just the pots were a disaster.

Until the second glaze firing done at the same time and with the same
materials came out perfect I had tried to convince myself that it was a
glazing problem (dirty pots) but it clearly isn't. I have never seen
anything like this and can't for the life of me reason out why it happened.

"annemarie" wrote in message
...

"dkat" wrote in message
...
We have been having problems with our kilns but our last firing is the
most
bizarre we have had to date. We fired 2 kilns starting at the same time
with the same ramping schedule. It is a modified version of MC6's
posted
version (Oxidation - cone six - Skutt electric kilns).

Segment Rate Temp Hold

1 100 220 0
2 350 2000 0
3 150 2180 25
4 500 1900 0
5 125 1400 0

Both kilns had comparable pots and the same glazes. Both showed the
same
cone characteristics (top shelf cone 5 flat cone six tipping and the
other
shelves show cone six past middle but not quite flat). #1 kiln took 18+
hours to fire and #5 kiln took about 14+ hours. The firing unless my
math
is
way off should have been about 13hours.


The glazes in kiln #1 were perfect though still overfired (a little
pitting
on one piece). The glazes in kiln #5 were a disaster. A large
percentage
of them had severe crawling. The glazes this showed up on are floating
blue, MC6 Spearmint, MC6 Bone, Raspberry - I think that is it. The
other
issue that we saw was a pot cracking as if their was a glaze fit problem
but
I think this is a different issue because I have been finding people
sneaking in non-studio underglazes and clays.

So... what are the thoughts on this?



Crawling is usually more about dust or something on the pot before
glazing.
I don't really have any answers, but maybe there were more odd underglazes
and clays there than you thought??
I found it difficult to work out your firing schedule, also I work in
centigrade. Why so complicated?
In my experience holding at different stages is not necessary usually. I
soak at top temp always for half an hour. I know when cooling periods of
soaking are necessary for crystaline glazes, but why so complicated for
these glazes?

Any chance that the lowest kiln shelf was only a few inches away from
the kiln floor in either of the kilns. I have found this to have a
large effect on the firing of the kiln if there is not sufficient space
below the bottom shelf (at least 6 inches).

could be that the problem is in the refire.. If the kiln had got most of the
way to temp then the glazes MAY have started to melt, and then frozen before
they fused... Cooled down and then refired they may have stayed crawled...
Just a thought
Course you could always put it down to the bad kiln fairy...
Hugs
Eddie
"dkat" wrote in message
...
This is the firing recommended on Mastering Cone 6 FAQ and I like it. We
are not doing the crystallized glazes (where you try to grow giant
crystals)
but our glazes do form crystals which is what gives the glazes a feeling
of
depth or color. Toby's red develops it's red color with slow cooling.
Floating Blue becomes opalescent. The glazes from MC6 for a satin matt
rather than a glossy clear.

Again, the two kilns had the exact same glazes, clay bodies for at least a
few of the pieces were clearly recognizable as 112, and there were
problems
with pots of experienced potters that I trust to tell me if they had used
outside clay or glazes and I could recognize the clay body and glazes on
most pieces in any case. I noticed that I left out one piece of
information. The kiln that had the crawling had not come to temperature
with an Error 1 and had to be refired. There was no error with the refire
and the cones looked fine. Just the pots were a disaster.

Until the second glaze firing done at the same time and with the same
materials came out perfect I had tried to convince myself that it was a
glazing problem (dirty pots) but it clearly isn't. I have never seen
anything like this and can't for the life of me reason out why it
happened.

"annemarie" wrote in message
...

"dkat" wrote in message
...
We have been having problems with our kilns but our last firing is the
most
bizarre we have had to date. We fired 2 kilns starting at the same
time
with the same ramping schedule. It is a modified version of MC6's
posted
version (Oxidation - cone six - Skutt electric kilns).

Segment Rate Temp Hold

1 100 220 0
2 350 2000 0
3 150 2180 25
4 500 1900 0
5 125 1400 0

Both kilns had comparable pots and the same glazes. Both showed the
same
cone characteristics (top shelf cone 5 flat cone six tipping and the
other
shelves show cone six past middle but not quite flat). #1 kiln took
18+
hours to fire and #5 kiln took about 14+ hours. The firing unless my
math
is
way off should have been about 13hours.


The glazes in kiln #1 were perfect though still overfired (a little
pitting
on one piece). The glazes in kiln #5 were a disaster. A large
percentage
of them had severe crawling. The glazes this showed up on are floating
blue, MC6 Spearmint, MC6 Bone, Raspberry - I think that is it. The
other
issue that we saw was a pot cracking as if their was a glaze fit
problem
but
I think this is a different issue because I have been finding people
sneaking in non-studio underglazes and clays.

So... what are the thoughts on this?



Crawling is usually more about dust or something on the pot before
glazing.
I don't really have any answers, but maybe there were more odd
underglazes
and clays there than you thought??
I found it difficult to work out your firing schedule, also I work in
centigrade. Why so complicated?
In my experience holding at different stages is not necessary usually. I
soak at top temp always for half an hour. I know when cooling periods of
soaking are necessary for crystaline glazes, but why so complicated for
these glazes?

"Eddie Daughton" wrote in message
...
could be that the problem is in the refire.. If the kiln had got most of
the way to temp then the glazes MAY have started to melt, and then frozen
before they fused... Cooled down and then refired they may have stayed
crawled...
Just a thought
Course you could always put it down to the bad kiln fairy...
Hugs
Eddie

Eddie could be right, the part fired, then refired could be the culprit. I
would get the kiln checked, see that all the elements are in good working
order and as someone else suggested make sure your bottom shelf is high
enough.
Thanks for the schedule answer, makes sense, good luck.
Annemarie

"dkat" wrote in message
...
This is the firing recommended on Mastering Cone 6 FAQ and I like it. We
are not doing the crystallized glazes (where you try to grow giant
crystals)
but our glazes do form crystals which is what gives the glazes a feeling
of
depth or color. Toby's red develops it's red color with slow cooling.
Floating Blue becomes opalescent. The glazes from MC6 for a satin matt
rather than a glossy clear.

Again, the two kilns had the exact same glazes, clay bodies for at least
a
few of the pieces were clearly recognizable as 112, and there were
problems
with pots of experienced potters that I trust to tell me if they had used
outside clay or glazes and I could recognize the clay body and glazes on
most pieces in any case. I noticed that I left out one piece of
information. The kiln that had the crawling had not come to temperature
with an Error 1 and had to be refired. There was no error with the
refire
and the cones looked fine. Just the pots were a disaster.

Until the second glaze firing done at the same time and with the same
materials came out perfect I had tried to convince myself that it was a
glazing problem (dirty pots) but it clearly isn't. I have never seen
anything like this and can't for the life of me reason out why it
happened.

"annemarie" wrote in message
...

"dkat" wrote in message
...
We have been having problems with our kilns but our last firing is the
most
bizarre we have had to date. We fired 2 kilns starting at the same
time
with the same ramping schedule. It is a modified version of MC6's
posted
version (Oxidation - cone six - Skutt electric kilns).

Segment Rate Temp Hold

1 100 220 0
2 350 2000 0
3 150 2180 25
4 500 1900 0
5 125 1400 0

Both kilns had comparable pots and the same glazes. Both showed the
same
cone characteristics (top shelf cone 5 flat cone six tipping and the
other
shelves show cone six past middle but not quite flat). #1 kiln took
18+
hours to fire and #5 kiln took about 14+ hours. The firing unless my
math
is
way off should have been about 13hours.


The glazes in kiln #1 were perfect though still overfired (a little
pitting
on one piece). The glazes in kiln #5 were a disaster. A large
percentage
of them had severe crawling. The glazes this showed up on are
floating
blue, MC6 Spearmint, MC6 Bone, Raspberry - I think that is it. The
other
issue that we saw was a pot cracking as if their was a glaze fit
problem
but
I think this is a different issue because I have been finding people
sneaking in non-studio underglazes and clays.

So... what are the thoughts on this?



Crawling is usually more about dust or something on the pot before
glazing.
I don't really have any answers, but maybe there were more odd
underglazes
and clays there than you thought??
I found it difficult to work out your firing schedule, also I work in
centigrade. Why so complicated?
In my experience holding at different stages is not necessary usually.
I
soak at top temp always for half an hour. I know when cooling periods
of
soaking are necessary for crystaline glazes, but why so complicated for
these glazes?

On Sun, 1 May 2005 14:46:20 -0400, "dkat"
wrote:

We have been having problems with our kilns but our last firing is the most
bizarre we have had to date. We fired 2 kilns starting at the same time
with the same ramping schedule. It is a modified version of MC6's posted
version (Oxidation - cone six - Skutt electric kilns).

Segment Rate Temp Hold

1 100 220 0
2 350 2000 0
3 150 2180 25
4 500 1900 0
5 125 1400 0

Both kilns had comparable pots and the same glazes. Both showed the same
cone characteristics (top shelf cone 5 flat cone six tipping and the other
shelves show cone six past middle but not quite flat). #1 kiln took 18+
hours to fire and #5 kiln took about 14+ hours. The firing unless my math is
way off should have been about 13hours.


The glazes in kiln #1 were perfect though still overfired (a little pitting
on one piece). The glazes in kiln #5 were a disaster. A large percentage
of them had severe crawling. The glazes this showed up on are floating
blue, MC6 Spearmint, MC6 Bone, Raspberry - I think that is it. The other
issue that we saw was a pot cracking as if their was a glaze fit problem but
I think this is a different issue because I have been finding people
sneaking in non-studio underglazes and clays.

So... what are the thoughts on this?


OK, I'm grasping at straws here. But suppose there was some
problem with kiln #5 that caused one or more elements to
shut down temporarily. (Loose connection, whatever.) Then
the controller is calling for heat and none is coming, so it can't
hold the programmed curve. BUT, the connection jiggles
back into place later, causing the controller to go to maximum
output to catch up. It catches up as far as the cone melting goes,
but the wares have gotten a really rapid temperature rise
along the way.

I think this would give the results you saw, though I'm not sure how
to test this idea. Or do you have a recording pyrometer setup?
If not, maybe you can run a test load and have someone check
the temps every hour.

Just a thought....




Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

"Bob Masta" wrote in message
...
On Sun, 1 May 2005 14:46:20 -0400, "dkat"
wrote:

We have been having problems with our kilns but our last firing is the
most
bizarre we have had to date. We fired 2 kilns starting at the same time
with the same ramping schedule. It is a modified version of MC6's posted
version (Oxidation - cone six - Skutt electric kilns).

Segment Rate Temp Hold

1 100 220 0
2 350 2000 0
3 150 2180 25
4 500 1900 0
5 125 1400 0

Both kilns had comparable pots and the same glazes. Both showed the same
cone characteristics (top shelf cone 5 flat cone six tipping and the
other
shelves show cone six past middle but not quite flat). #1 kiln took 18+
hours to fire and #5 kiln took about 14+ hours. The firing unless my math
is
way off should have been about 13hours.


The glazes in kiln #1 were perfect though still overfired (a little
pitting
on one piece). The glazes in kiln #5 were a disaster. A large percentage
of them had severe crawling. The glazes this showed up on are floating
blue, MC6 Spearmint, MC6 Bone, Raspberry - I think that is it. The other
issue that we saw was a pot cracking as if their was a glaze fit problem
but
I think this is a different issue because I have been finding people
sneaking in non-studio underglazes and clays.

So... what are the thoughts on this?


OK, I'm grasping at straws here. But suppose there was some
problem with kiln #5 that caused one or more elements to
shut down temporarily. (Loose connection, whatever.) Then
the controller is calling for heat and none is coming, so it can't
hold the programmed curve. BUT, the connection jiggles
back into place later, causing the controller to go to maximum
output to catch up. It catches up as far as the cone melting goes,
but the wares have gotten a really rapid temperature rise
along the way.

I think this would give the results you saw, though I'm not sure how
to test this idea. Or do you have a recording pyrometer setup?
If not, maybe you can run a test load and have someone check
the temps every hour.

Just a thought....




Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator

We are a crafs center at a University so I can imagine this happening. I'm
actually hoping that it was a one time event due to something like this (in
the years the studio has been going we haven't had this happen). I'm real
uneasy about risking student's work by trying to run the ramp firing again
given that the old programmed 'slow cone 6' had worked just fine until it
failed on the last firing. I'm tempted at this point to just attribute that
to an interrupt in the schools electrical power and to stick with what has
been known to work.

In the mean time I have lots to chew on. Thank you all. Donna