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iron red refired

updated wed 12 mar 03

 

William Jacob on sun 9 mar 03


I've looked in the archives, but haven't found any answer to this question. Can anyone tell me why I have to refire ^6 iron red glazes to ^04 to get them to come out a decent red/orange color? Can you explain what's going on chemically or physically? If I fire it again back to ^6 it goes back to the original green brown snotty color.
Just curious. And I don't expect an answer anytime soon because I know all you lucky bastards will be living it up in sunny San Diego. Have a great time, wish I was there.
Thanks,
joebugs

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John Hesselberth on sun 9 mar 03


Hi Joebugs,

Crystal growth is the answer to your question. If you cool slowly from=20=

1900 down to about 1500 instead of just turning the kiln off, you can=20
get the effect with a single cone 6 firing. Slow the cooling rate down=20=

to 125=B0F/hr through that zone. You may have to adjust it up or down a=20=

little from there to get the best results. When you just shut your=20
kiln off after reaching cone 6 it drops through that temperature range=20=

too fast to allow good crystal growth.

Regards,

John

On Sunday, March 9, 2003, at 11:56 AM, William Jacob wrote:

> I've looked in the archives, but haven't found any answer to this=20
> question. Can anyone tell me why I have to refire ^6 iron red glazes=20=

> to ^04 to get them to come out a decent red/orange color? Can you=20
> explain what's going on chemically or physically? If I fire it again=20=

> back to ^6 it goes back to the original green brown snotty color.
> Just curious. And I don't expect an answer anytime soon because I=20
> know all you lucky bastards will be living it up in sunny San Diego.=20=

> Have a great time, wish I was there.
http://www.frogpondpottery.com
http://www.masteringglazes.com

Carol Tripp on mon 10 mar 03


I'll have to wade in here and say that some iron reds need both a slow cool
from ^6 and a refire to ^04.
Best regards,
Carol
Dubai, UAE






>From: John Hesselberth
>>Hi Joebugs,
>
>Crystal growth is the answer to your question. If you cool slowly from
>1900 down to about 1500 instead of just turning the kiln off, you can get
>the effect with a single cone 6 firing. Slow the cooling rate down to
>125F/hr through that zone. You may have to adjust it up or down a little
>from there to get the best results. When you just shut your kiln off after
>reaching cone 6 it drops through that temperature range too fast to allow
>good crystal growth.
>Regards,
>
>John
>
>On Sunday, March 9, 2003, at 11:56 AM, William Jacob wrote:
>
>>I've looked in the archives, but haven't found any answer to this
>>question. Can anyone tell me why I have to refire ^6 iron red glazes to
>>^04 to get them to come out a decent red/orange color? Can you explain
>>what's going on chemically or physically? If I fire it again back to ^6 it
>>goes back to the original green brown snotty color.
>> Just curious. And I don't expect an answer anytime soon because I know
>>all you lucky bastards will be living it up in sunny San Diego. Have a
>>great time, wish I was there.
>

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Ron Roy on tue 11 mar 03


Hi Carol,

This means they need a slower cool - when you refire you get crystal
forming on the way up and on the way down - if you don't go high enough to
start melting them again. If you calculate how much extra time it takes for
the 2nd firing - say from 800C up to bisque temp - you can simply extend
the slow cool cycle and get the same results - may take some trial and
error but it would be well worth it.



>I'll have to wade in here and say that some iron reds need both a slow cool
>from ^6 and a refire to ^04.
>Best regards,
>Carol
>Dubai, UAE

Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513

William Jacob on tue 11 mar 03


Thanks to all.
Sorry in my first post I didn't mention my firing scchhedule.
I've been cooling from ^6 down to 1950F naturally. Then from 1950-1500 at 150F per hour. Then naturally down from that.
I'll try three things.
1. I got some RIO which is not so liver colored.
2. I'll try slowing the cooling from 1950-1500 at 125F per hour.
3. I'll try a soak at 1900F. Maybe 30 minutes.
We'll see. Again, thanks.

To John & Ron: You guys are a gift to us all. Thanks for sharing your knowledge. Great book. And to think, before I found clayart, I thought I was a freak for loving glaze testing.


--- Carol Tripp wrote:
>I'll have to wade in here and say that some iron reds need both a slow cool
>from ^6 and a refire to ^04.
>Best regards,
>Carol
>Dubai, UAE
>
>>From: John Hesselberth
>>>Hi Joebugs,
>>
>>Crystal growth is the answer to your question. If you cool slowly from 1900 down to about 1500 instead of just turning the kiln off, you can get the effect with a single cone 6 firing. Slow the cooling rate down to 125F/hr through that zone. You may have to adjust it up or down a little from there to get the best results. When you just shut your kiln off after reaching cone 6 it drops through that temperature range too fast to allow good crystal growth.
>>Regards,
>>
>>John
>>
>>On Sunday, March 9, 2003, at 11:56 AM, William Jacob wrote:
>>
>>>I've looked in the archives, but haven't found any answer to this question. Can anyone tell me why I have to refire ^6 iron red glazes to ^04 to get them to come out a decent red/orange color? Can you explain what's going on chemically or physically? If I fire it again back to ^6 it goes back to the original green brown snotty color.

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John Post on tue 11 mar 03


Here's another couple of things to try...
Try cooling at 150F from 1900-1300. I get good iron reds that way...another
thing to try is an iron red line blend. Double the amount of iron in your
glaze and do a line blend by volume with your original glaze... What I have
found by doing this is that the faster you cool, the more iron you need in
the glaze, the slower the cool, the less iron you need to get the same
effect...

Cheers,
John Post

Sorry in my first post I didn't mention my firing scchhedule.
I've been cooling from ^6 down to 1950F naturally. Then from 1950-1500 at
150F per hour. Then naturally down from that.
I'll try three things.
1. I got some RIO which is not so liver colored.
2. I'll try slowing the cooling from 1950-1500 at 125F per hour.
3. I'll try a soak at 1900F. Maybe 30 minutes.
We'll see. Again, thanks.

Carol Tripp on wed 12 mar 03


Gee, Ron, I'm already cooling at 50C/hour, from 1037C down to 750C. How
much slower do I need to go? (Can you hear the whine in that question?) I
might add that it is only for one particular iron red, Persimmon, that I
need to do the glaze then refire to bisque routine. After a glaze fire, it
is ketchup and mustard and the bisque fire makes the mustard go away.
Best regards,
Carol
Dubai, UAE


Ron wrote:
>This means they need a slower cool - when you refire you get crystal
>forming on the way up and on the way down - if you don't go high enough to
>start melting them again. If you calculate how much extra time it takes for
>the 2nd firing - say from 800C up to bisque temp - you can simply extend
>the slow cool cycle and get the same results - may take some trial and
>error but it would be well worth it.
>
>
>
> >I'll have to wade in here and say that some iron reds need both a slow
>cool
> >from ^6 and a refire to ^04.
> >Best regards,
> >Carol
> >Dubai, UAE
>
>Ron Roy
>RR#4
>15084 Little Lake Road
>Brighton, Ontario
>Canada
>K0K 1H0
>Phone: 613-475-9544
>Fax: 613-475-3513
>
>______________________________________________________________________________
>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.


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