MJ on mon 4 apr 11
Hello John - I just bought laguna cone 5 b-mix and I would like to get some
input on the firing schedule that you use. After I bought it, a friend tol=
d
me that they had gotten bloating when they fired that clay to cone 6. I
have had others tell me that it works fine at cone 6 and they have actually
fired it to cone 7 with no problems. I usually bisque fire to cone 05 - bu=
t
I see that you bisque to cone 06. When I do my glaze firing, I fire to con=
e
5 but I add a 30 minute hold and the witness cones show the cone 6 cone
completely down and the cone 7 cone just starting to tip. I do a slow glaz=
e
and also a slow cool using a somewhat modified MC6G schedule. I am just
starting to use some of the MC6G glazes and their firing schedule actually
goes a bit higher, but with a shorter hold. I am curious to know how high
you fire your b-mix. Sounds like it works well for you. I looked through
the clayart archives and I have seen talk about both bloating and successfu=
l
firings higher. The posts are a couple of years old and I wonder if Laguna
would have addressed the bloating issue at cone 6. My b-mix is coming from
the Los Angeles plant in case that makes a difference. Thanks in advance
for your help. MJ
On Sun, Apr 3, 2011 at 7:23 PM, John Rodgers wrote:
> Kristina,
>
> First, I think firing your bisque B-mix to 03 is a little hot. I guess
> some may do it, but through experience, I find that 06 works well for
> Laguna's C-5 B-mix.
>
> I use Laguna C-5 B-mix for nearly all my work. It is my core clay. When
> I make plates, I do not stack them. I bisque the plate on a flat
> surface, no stacking. Like you, I had cracking when I started out. Now I
> begin by coating the surface of a shelf with loose alumina hydrate
> spread thin, then put the plate on that, bisque firing it right side up
> to cone 06. The alumina hydrate acts like little ball bearings allowing
> the plate to slide as it shrinks during the firing. If any part of the
> plate sticks while the rest shrinks - the plate will crack. So the
> sliding action helps. This works for me. Others do it different.
>
> One last thing .... absolutely DO NOT open your kiln until it is at room
> temperature. It is very easy to set up a situation where the rim is
> cooling faster than the center of the plate and this will guarantee
> cracking every time. When I started out, in a full kiln load of plates,
> I cracked every plate in there but one right through the middle into two
> pieces trying to push it. Only the top plate survived. The plates down
> through the stack of shelves were hot in the center and cooling much to
> fast on the outside edge. CRACK!!! Lesson learned.
>
> Good luck.
>
> John
>
> John Rodgers
> Clayartist and Moldmaker
> 88'GL VW Bus Driver
> Chelsea, AL
> Http://www.moldhaus.com
>
>
> On 4/3/2011 6:24 PM, Kristina Chadwick wrote:
>
>> I have limited experience making plates, but due to a request I've been
>> making them without much success. During the bisque fire the majority of
>> the
>> plates are cracking in half, right down the middle. There are no S crack=
s
>> present. I am using Laguna B-mix, cone 5. I am bisque firing to cone 03 =
in
>> an electric kiln. Plates were stacked for firing (6 total, the bottom 4
>> cracked in half, top 2 survived intact).
>>
>> The plates are ~ 7-8" in diameter with a gradual rise along the edge lik=
e
>> a
>> traditional dinner plate. They are about 0.25" thick. The last time I ma=
de
>> plates there was also a lot of cracking (mostly in half), but I thought =
it
>> was related to S cracks, so I threw these thicker.
>>
>> All plates in this last batch were thrown the same day and dried the sam=
e
>> amount of time.
>>
>> I'd appreciate any advice, the low yield is utterly frustrating!
>>
>> Thanks,
>> Kristina
>>
>> P.S. I can take a picture if that would help diagnose the problem.
>>
>>
>>
Sumi von Dassow on wed 6 apr 11
MJ
I use Laguna cone 5 B-Mix for most of my work. I fire to cone 6 electric
and cone 7 reduction with no trouble. In fact I have even fired it at
cone 8 in my little tiny wood kiln. A couple of years ago when I was
first learning to fire my gas kiln I found that on the bottom of the
kiln where it got the hottest the cone 5 b-mix would bloat - but I think
that was largely in pots made from recycled clay, or clay that had been
badly wedged. I started getting cone 10 b-mix for the students until I
was sure they wouldn't have problems with it but we are all back to the
cone 5. I have the firing better under control now and the kiln is now
firing very evenly and I have not had any problems with bloating lately.
Certainly I have never had a problem at cone 6 oxidation.
Sumi
> Hello John - I just bought laguna cone 5 b-mix and I would like to get so=
me
> input on the firing schedule that you use. After I bought it, a friend t=
old
> me that they had gotten bloating when they fired that clay to cone 6. I
> have had others tell me that it works fine at cone 6 and they have actual=
ly
> fired it to cone 7 with no problems. I usually bisque fire to cone 05 - =
but
> I see that you bisque to cone 06. When I do my glaze firing, I fire to c=
one
> 5 but I add a 30 minute hold and the witness cones show the cone 6 cone
> completely down and the cone 7 cone just starting to tip. I do a slow gl=
aze
> and also a slow cool using a somewhat modified MC6G schedule. I am just
> starting to use some of the MC6G glazes and their firing schedule actuall=
y
> goes a bit higher, but with a shorter hold. I am curious to know how hig=
h
> you fire your b-mix. Sounds like it works well for you. I looked throug=
h
> the clayart archives and I have seen talk about both bloating and success=
ful
> firings higher. The posts are a couple of years old and I wonder if Lagu=
na
> would have addressed the bloating issue at cone 6. My b-mix is coming fr=
om
> the Los Angeles plant in case that makes a difference. Thanks in advance
> for your help. MJ
>
> On Sun, Apr 3, 2011 at 7:23 PM, John Rodgers wrote:
>
>
>> Kristina,
>>
>> First, I think firing your bisque B-mix to 03 is a little hot. I guess
>> some may do it, but through experience, I find that 06 works well for
>> Laguna's C-5 B-mix.
>>
>> I use Laguna C-5 B-mix for nearly all my work. It is my core clay. When
>> I make plates, I do not stack them. I bisque the plate on a flat
>> surface, no stacking. Like you, I had cracking when I started out. Now I
>> begin by coating the surface of a shelf with loose alumina hydrate
>> spread thin, then put the plate on that, bisque firing it right side up
>> to cone 06. The alumina hydrate acts like little ball bearings allowing
>> the plate to slide as it shrinks during the firing. If any part of the
>> plate sticks while the rest shrinks - the plate will crack. So the
>> sliding action helps. This works for me. Others do it different.
>>
>> One last thing .... absolutely DO NOT open your kiln until it is at room
>> temperature. It is very easy to set up a situation where the rim is
>> cooling faster than the center of the plate and this will guarantee
>> cracking every time. When I started out, in a full kiln load of plates,
>> I cracked every plate in there but one right through the middle into two
>> pieces trying to push it. Only the top plate survived. The plates down
>> through the stack of shelves were hot in the center and cooling much to
>> fast on the outside edge. CRACK!!! Lesson learned.
>>
>> Good luck.
>>
>> John
>>
>> John Rodgers
>> Clayartist and Moldmaker
>> 88'GL VW Bus Driver
>> Chelsea, AL
>> Http://www.moldhaus.com
>>
>>
>> On 4/3/2011 6:24 PM, Kristina Chadwick wrote:
>>
>>
>>> I have limited experience making plates, but due to a request I've been
>>> making them without much success. During the bisque fire the majority o=
f
>>> the
>>> plates are cracking in half, right down the middle. There are no S crac=
ks
>>> present. I am using Laguna B-mix, cone 5. I am bisque firing to cone 03=
in
>>> an electric kiln. Plates were stacked for firing (6 total, the bottom 4
>>> cracked in half, top 2 survived intact).
>>>
>>> The plates are ~ 7-8" in diameter with a gradual rise along the edge li=
ke
>>> a
>>> traditional dinner plate. They are about 0.25" thick. The last time I m=
ade
>>> plates there was also a lot of cracking (mostly in half), but I thought=
it
>>> was related to S cracks, so I threw these thicker.
>>>
>>> All plates in this last batch were thrown the same day and dried the sa=
me
>>> amount of time.
>>>
>>> I'd appreciate any advice, the low yield is utterly frustrating!
>>>
>>> Thanks,
>>> Kristina
>>>
>>> P.S. I can take a picture if that would help diagnose the problem.
>>>
>>>
>>>
>>>
>
>
>
--
Sumi von Dassow
www.herwheel.com
sumi@herwheel.com
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