Alisa Clausen on thu 4 mar 04
>What you don't want to do is start remelting the crystals that have
already
>formed when refiring - I would guess a low bisque (06) might work better
>than one at cone 04 for many cone 6 glazes by the way - especially those
>high in boron.
Ron, this is excellent information. I had refired some small pots that
were lined with a crystal glaze, in a luster firing, straight up to 850c
and shut off kiln. The crystals, that had been small and clear, were gone
and the entire glaze went muddy and murky. I understand now why this
occured.
I wonder if I fired a luster up to 850c with a hold on the way down to 600c,
if the cyrstals would reform. Or, what is the miniumum temp. I could get
the lusters to melt, while not melting the crystals? I would have to make
a lot of tries I think. I do very little of this type of work, so I am not
sure how much time I would spend on the firings and the expense of it.
Intersting information for sure.
regards from Alisa in Denmark
Ron Roy on sat 6 mar 04
Hi Alisa,
Yes - each glaze will have a different melting point as will each crystal
type. The smaller the crystal the faster it will melt.
The only way to find out what the best temperature to go to - to not melt a
crystal - is to do the experiments.
There is a type of kiln - called a gradient kiln - that will fire a bar of
clay at different temperatures That would be the ideal way to do it. All
you have to do is fine someone who has one and who will fire some samples
for you.
Yes - the crystals will reform if you hold at the right temperature - it is
a reversible process. If - you have melted the "seed" material the crystals
will take longer to reform. Seeds (refractory material - not melted) give
crystals a head start - some thing to form on - it's why rutile is added to
some crystalline glazes because TiO2 is hard to melt.
RR
>I wonder if I fired a luster up to 850c with a hold on the way down to 600c,
>if the cyrstals would reform. Or, what is the miniumum temp. I could get
>the lusters to melt, while not melting the crystals? I would have to make
>a lot of tries I think. I do very little of this type of work, so I am not
>sure how much time I would spend on the firings and the expense of it.
>Intersting information for sure.
>
>regards from Alisa in Denmark
>
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Ron Roy
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