search  current discussion  categories  kilns & firing - misc 

iron red refired - for carol in dubai

updated thu 27 mar 03


Ron Roy on wed 26 mar 03

Hi Carol,

Just back from a short vacation and someone saved this for me.

Something fishy here - could it be this particular glaze needs cooling at a
lower range. I do know from some of my dilatometry that some that some of
the high boron glazes simply do not solidify until below 600C - some even
below that. We need to remember that when refired in a bisque firing that
the crystallization process happen on the way up and on the way down so it
makes me think you should try slow cooling say from 750C down to 550C at
say 25C per hour.

The other factor might be the reduction that happens in bisque firing.

Keep talking about this - someone is going to come up with something sooner
or later.

I should add here - when I refired a test of my cone 10 reduction Tenmoku
I get a lot of "mustard" not a pretty sight - could this be a clue?


> 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,
> is ketchup and mustard and the bisque fire makes the mustard go away.
> Best regards,
> Carol
> Dubai, UAE

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