Cold spots in kiln - usual or unusual ?

Hi All
I've been using a little Paragon SC2 front-loading kiln for the last 6
weeks or so - mostly making small fused pendant pieces, dichro,
earrings - that sort of thing.

I'd noticed that not all of the pieces in each firing were fusing
fully - and recently seem to have discovered that the 'bad' pieces are
located at the front and right side of the kiln.

Things came to a head the other day when I tried fusing a large piece
of glass (well - 5" diameter - which is large in relation to the size
of the kiln). The left side of the piece fused well - but the right
side was less well fused.

I wondered if there was a problem with the kiln door not closing
tightly, and tried, on the last couple of firings, to introduce a
'gasket' of fiber-paper around the door - not sure yet if it makes any
great difference. Paragon say that the door gap is to allow for
expansion.... and suggest that I 'bring the glass up slower as to heat
soak the ware to it maximum'

I guess the question I'm asking is - 'Is it normal that you get hot /
cold spots in a small kiln like this ?'
If it's normal, should I simply increase the time at the top
temperature so that the 'cold' spots get hot enough to fully fuse -
it's a pain and time-consuming at the moment to have to re-fire pieces
that didn't work the first time around..

Any sugestions welcomed
Thanks
Adrian

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Adrian Brentnall wrote:
Hi All
I've been using a little Paragon SC2 front-loading kiln for the last 6
weeks or so - mostly making small fused pendant pieces, dichro,
earrings - that sort of thing.

I'd noticed that not all of the pieces in each firing were fusing
fully - and recently seem to have discovered that the 'bad' pieces are
located at the front and right side of the kiln.

Things came to a head the other day when I tried fusing a large piece
of glass (well - 5" diameter - which is large in relation to the size
of the kiln). The left side of the piece fused well - but the right
side was less well fused.

I wondered if there was a problem with the kiln door not closing
tightly, and tried, on the last couple of firings, to introduce a
'gasket' of fiber-paper around the door - not sure yet if it makes any
great difference. Paragon say that the door gap is to allow for
expansion.... and suggest that I 'bring the glass up slower as to heat
soak the ware to it maximum'

I guess the question I'm asking is - 'Is it normal that you get hot /
cold spots in a small kiln like this ?'
If it's normal, should I simply increase the time at the top
temperature so that the 'cold' spots get hot enough to fully fuse -
it's a pain and time-consuming at the moment to have to re-fire pieces
that didn't work the first time around..

Any sugestions welcomed
Thanks
Adrian

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Try approaching the top temperature and/or soak a bit longer. Then note
if the "hot" side is overdone.

--
Jack

bobo1148atxmissiondotcom


http://photos.yahoo.com/bc/xmissionbobo/

HI Jack

On Thu, 01 Dec 2005 15:59:50 -0700, nJb wrote:

Adrian Brentnall wrote:
Hi All
I've been using a little Paragon SC2 front-loading kiln for the last 6
weeks or so - mostly making small fused pendant pieces, dichro,
earrings - that sort of thing.

I'd noticed that not all of the pieces in each firing were fusing
fully - and recently seem to have discovered that the 'bad' pieces are
located at the front and right side of the kiln.

Things came to a head the other day when I tried fusing a large piece
of glass (well - 5" diameter - which is large in relation to the size
of the kiln). The left side of the piece fused well - but the right
side was less well fused.

I wondered if there was a problem with the kiln door not closing
tightly, and tried, on the last couple of firings, to introduce a
'gasket' of fiber-paper around the door - not sure yet if it makes any
great difference. Paragon say that the door gap is to allow for
expansion.... and suggest that I 'bring the glass up slower as to heat
soak the ware to it maximum'

I guess the question I'm asking is - 'Is it normal that you get hot /
cold spots in a small kiln like this ?'
If it's normal, should I simply increase the time at the top
temperature so that the 'cold' spots get hot enough to fully fuse -
it's a pain and time-consuming at the moment to have to re-fire pieces
that didn't work the first time around..

Any sugestions welcomed
Thanks
Adrian

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Try approaching the top temperature and/or soak a bit longer. Then note
if the "hot" side is overdone.

Thanks - I'll give that a try.
I'm currently soaking at 820c for 20-30 mins - guess I could increase
the time a bit. As pieces are fine after a 'second go' - I suppose 40
- 50 mins would be a good starting point..?

Thanks again
Adrian
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Adrian Brentnall wrote:


Thanks - I'll give that a try.
I'm currently soaking at 820c for 20-30 mins - guess I could increase
the time a bit. As pieces are fine after a 'second go' - I suppose 40
- 50 mins would be a good starting point..?

Thanks again
Adrian
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That should work but it does seem odd that the fusing would be that
uneven. Often I soak at a lower temp (1480F-805C) for an hour.

You might want to see this:

http://www.bullseyeglass.com/pdfs/te...chNotes_01.pdf


Pages of good info he

http://www.bullseyeglass.com/connection/education/


And the best fusing forum on the net:

http://www.warmglass.com/phpBB/index.php
--
Jack

bobo1148atxmissiondotcom


http://photos.yahoo.com/bc/xmissionbobo/

Every kiln has cold spots - some more serious than others. The trick
is to identify where they are and either work around or with them.

For firing schedules, I suggest a computer program that will provide
every one you'll ever need.
http://www.prleap.com/pr/18276

Dennis Brady
http://www.debrady.com
http://www.victorianartglass.biz
http://www.glasscampus.com

Hi

On Thu, 01 Dec 2005 18:50:26 -0700, nJb wrote:

Adrian Brentnall wrote:


Thanks - I'll give that a try.
I'm currently soaking at 820c for 20-30 mins - guess I could increase
the time a bit. As pieces are fine after a 'second go' - I suppose 40
- 50 mins would be a good starting point..?

Thanks again
Adrian
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That should work but it does seem odd that the fusing would be that
uneven. Often I soak at a lower temp (1480F-805C) for an hour.

Thanks - I might give that a try...


You might want to see this:

http://www.bullseyeglass.com/pdfs/te...chNotes_01.pdf

Looks interesting, I'll read it in the bath tonight g


Pages of good info he

http://www.bullseyeglass.com/connection/education/


And the best fusing forum on the net:

http://www.warmglass.com/phpBB/index.php

Been there - bags of info for the searching - but not an enormous
amount of response to my query....


I found a bit in Petra Kaiser's book - suggested that a possible
problem with small kilns like the SC2 is that they heat up very
quickly (compared to a large kiln).

She points out that the thermocouple measures air temp - not glass
temp - so even though the air might be at a good 820c then glass may
not have caught up quite.

Your plan of 'cooler for longer' might be the solution - I'll give it
a go g....

Many thanks
Adrian

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HI Dennis

On 1 Dec 2005 18:40:51 -0800, wrote:

Every kiln has cold spots - some more serious than others. The trick
is to identify where they are and either work around or with them.

Yes - understood... all part of the learning process g


For firing schedules, I suggest a computer program that will provide
every one you'll ever need.
http://www.prleap.com/pr/18276

Looks interesting - if a bit more than I need just at the moment -
thanks !

Adrian


Dennis Brady
http://www.debrady.com
http://www.victorianartglass.biz
http://www.glasscampus.com

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wrote:

Every kiln has cold spots - some more serious than others. The trick
is to identify where they are and either work around or with them.

For firing schedules, I suggest a computer program that will provide
every one you'll ever need.
http://www.prleap.com/pr/18276

I think that would take much of the creativity out of fusing. I wouldn't
want some programmer deciding my firing schedules. Might be great for
mass production.

--
Jack

bobo1148atxmissiondotcom


http://www.glassartguild.com/gallery/jack_bowman

HI Jack

On Fri, 02 Dec 2005 21:34:00 -0700, nJb wrote:

wrote:

Every kiln has cold spots - some more serious than others. The trick
is to identify where they are and either work around or with them.

For firing schedules, I suggest a computer program that will provide
every one you'll ever need.
http://www.prleap.com/pr/18276

I think that would take much of the creativity out of fusing. I wouldn't
want some programmer deciding my firing schedules. Might be great for
mass production.

Hmmm
I couldn't see where the price was stated (which always worries me
g) - also not sure how it would help my current problem with the
incomplete fusing.

Like the idea on the bullseye reference that you gave - making up
little test pieces and 'calibrating' the kiln's performance that way.

I've not had a chance to try the slower ramp-up times (displaying at
one art show and another small sale this weekend) - but when it gets
quieter I'll try it & report back ...

Thanks
Adrian
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Hey Guys,
This post from Dec. 1st has shown up on my news reader as new today even
though I have already read it and deleted it before. I have been noticing
this problem lately on my groups. Has anyone else had this problem? Are
the servers burping 8-}

--
Connie Ryman
Cryman Studio

"Adrian Brentnall" adrian-the papers and the wrote
in message ...
Hi All
I've been using a little Paragon SC2 front-loading kiln for the last 6
weeks or so - mostly making small fused pendant pieces, dichro,
earrings - that sort of thing.

I'd noticed that not all of the pieces in each firing were fusing
fully - and recently seem to have discovered that the 'bad' pieces are
located at the front and right side of the kiln.

Things came to a head the other day when I tried fusing a large piece
of glass (well - 5" diameter - which is large in relation to the size
of the kiln). The left side of the piece fused well - but the right
side was less well fused.

I wondered if there was a problem with the kiln door not closing
tightly, and tried, on the last couple of firings, to introduce a
'gasket' of fiber-paper around the door - not sure yet if it makes any
great difference. Paragon say that the door gap is to allow for
expansion.... and suggest that I 'bring the glass up slower as to heat
soak the ware to it maximum'

I guess the question I'm asking is - 'Is it normal that you get hot /
cold spots in a small kiln like this ?'
If it's normal, should I simply increase the time at the top
temperature so that the 'cold' spots get hot enough to fully fuse -
it's a pain and time-consuming at the moment to have to re-fire pieces
that didn't work the first time around..

Any sugestions welcomed
Thanks
Adrian

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