dalecochoy on tue 30 mar 04
I have a question about refiring glazed pots.
I've seen a few comments on this, mostly for re-coating to cover better, but
here's the interest I have.
If I final fire a cone 6, or cone 10 glaze on a corresponding cone clay
and then want to try some further techniques at a lower firing temp, say 04
temp glaze , at what point does the previously fired glaze become fluid
enough so the other glaze won't slide off or pop off later. Does a cone 10
glaze, for instance, need that temp AGAIN to be fluid or once fired has that
chemical function disappeared. Does it get "fluid" at some earlier temp
after it's been fired ?
Is there a temp range where ANY glaze will again become fluid once fired.
I've tried a few things and thusfar haven't seen any problems but have
always wondered about the chemical/heat reaction AFTER the glaze has gone
through it's set technique.
Regards,
Dale Cochoy
Ron Roy on tue 30 mar 04
Hi Dale,
I have some understanding about this because - when I measure the
expansion/contraction of glazes in my dilatometer I can see when the glaze
softens - in fact if I let the heating go too far - the sample starts
sticking to the holder, push rod and thermocouple - an expensive repair.
The cone 10 glazes I have measured - maybe 50 - have all started to soften
between 700C and 900C. It depends on a number of factors - how high or low
the viscosity of the glass is - the running glazes tend to soften at the
lower temperature - and the stiff glazes at the higher temp.
A more important factor perhaps would be - once you are over the softening
stage - how slow you fire or how long you soak will probably have a greater
effect on the bonding and inter mixing.
Going to a lower temp and soaking will help the bond but minimize the
mixing for instance.
Keep good records and if you want help in predicting what to expect from
different types of glazes I will be happy to help.
RR
>I have a question about refiring glazed pots.
>I've seen a few comments on this, mostly for re-coating to cover better, but
>here's the interest I have.
>If I final fire a cone 6, or cone 10 glaze on a corresponding cone clay
>and then want to try some further techniques at a lower firing temp, say 04
>temp glaze , at what point does the previously fired glaze become fluid
>enough so the other glaze won't slide off or pop off later. Does a cone 10
>glaze, for instance, need that temp AGAIN to be fluid or once fired has that
>chemical function disappeared. Does it get "fluid" at some earlier temp
>after it's been fired ?
>Is there a temp range where ANY glaze will again become fluid once fired.
>I've tried a few things and thusfar haven't seen any problems but have
>always wondered about the chemical/heat reaction AFTER the glaze has gone
>through it's set technique.
>Regards,
>
>Dale Cochoy
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
dalecochoy on tue 30 mar 04
Thanks Ron, I may be getting back to you with some more precise questions.
Dale
----- Original Message -----
From: "Ron Roy"
To:
Sent: Tuesday, March 30, 2004 6:12 PM
Subject: Re: Firing different cone glazes over previously fired glazes?
> Hi Dale,
> I have some understanding about this because - when I measure the
> expansion/contraction of glazes in my dilatometer I can see when the glaze
> softens - in fact if I let the heating go too far - the sample starts
> sticking to the holder, push rod and thermocouple - an expensive repair.
>
> The cone 10 glazes I have measured - maybe 50 - have all started to soften
> between 700C and 900C. It depends on a number of factors - how high or low
> the viscosity of the glass is - the running glazes tend to soften at the
> lower temperature - and the stiff glazes at the higher temp.
>
> A more important factor perhaps would be - once you are over the softening
> stage - how slow you fire or how long you soak will probably have a
greater
> effect on the bonding and inter mixing.
>
> Going to a lower temp and soaking will help the bond but minimize the
> mixing for instance.
>
> Keep good records and if you want help in predicting what to expect from
> different types of glazes I will be happy to help.
>
> RR
>
> >I have a question about refiring glazed pots.
> >I've seen a few comments on this, mostly for re-coating to cover better,
but
> >here's the interest I have.
> >If I final fire a cone 6, or cone 10 glaze on a corresponding cone clay
> >and then want to try some further techniques at a lower firing temp, say
04
> >temp glaze , at what point does the previously fired glaze become fluid
> >enough so the other glaze won't slide off or pop off later. Does a cone
10
> >glaze, for instance, need that temp AGAIN to be fluid or once fired has
that
> >chemical function disappeared. Does it get "fluid" at some earlier temp
> >after it's been fired ?
> >Is there a temp range where ANY glaze will again become fluid once fired.
> >I've tried a few things and thusfar haven't seen any problems but have
> >always wondered about the chemical/heat reaction AFTER the glaze has gone
> >through it's set technique.
> >Regards,
> >
> >Dale Cochoy
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
> Phone: 613-475-9544
> Fax: 613-475-3513
dalecochoy on wed 31 mar 04
Thanks for the below Ron,
I was going to pusue this off-line with Ron but thought others might be
interested since he was the only one who responded with any knowledge of
what I was asking about.
Do I understand correctly then that if I would be refiring an already fired
cone 6 glaze (with something lower fire over top) that it would ALSO
resoften at the same 700-900C range that you found cone 10 glazes do., OR is
does cone 6 glaze resoften at a different temp?
I understand your point about slow firing/soaking once I reach that range.
This should not be a problem as I don't think anyone on earth fires slower
than me! :>)
In the few I've done I have had good ( apparent) bonding but don't see
"mixing" to my eyes. I don't really want them mixed anyhow for my
purposes, just bonded.
Thanks,
Dale
----- Original Message -----
From: "Ron Roy"
Subject: Re: Firing different cone glazes over previously fired glazes?
> I have some understanding about this because - when I measure the
> expansion/contraction of glazes in my dilatometer I can see when the glaze
> softens - in fact if I let the heating go too far - the sample starts
> sticking to the holder, push rod and thermocouple - an expensive repair.
>
> The cone 10 glazes I have measured - maybe 50 - have all started to soften
> between 700C and 900C. It depends on a number of factors - how high or low
> the viscosity of the glass is - the running glazes tend to soften at the
> lower temperature - and the stiff glazes at the higher temp.
>
> A more important factor perhaps would be - once you are over the softening
> stage - how slow you fire or how long you soak will probably have a
greater
> effect on the bonding and inter mixing.
>
> Going to a lower temp and soaking will help the bond but minimize the
> mixing for instance.
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