mel jacobson on sun 18 oct 09
i just turned my kiln off of two hours of down firing.
i am convinced that more things happen when you cool
than when you fire.
many have proven that correct.
and lots of icky things happen when you bisque fire too fast.
if you depend on books written in 1930 you may
just fire like 1930.
it is almost 2010.
and, my favorite form of ceramics is when
you peek in the kiln with a flashlight.
and you see a racer.
hooooooooooooooooooooozah
but, i still love leather hard.
from: minnetonka, mn
website: http://www.visi.com/~melpots/
clayart link: http://www.visi.com/~melpots/clayart.html
new book: http://www.21stcenturykilns.com
L TURNER on sun 18 oct 09
Mel,
I am appreciative and supportive of the new ideas that are being found
for firing.
The resulting pots are awesome
a couple of questions:
how big is your "big kiln"? I estimate from your posts that from
fires on to fires off was a total of 14-16 hours. Is this about
right?
Has anyone explained how and why a controlled cool down produces the
results that are being seen?
and especially for the reduction atmosphere?
What is your explanation for why these techniques were never tried
during the 1930's (your textbook reference)?
Regards,
L. Turner,
The Woodlands, TX
mel jacobson on sun 18 oct 09
here are some simple answers.
i sure do not have all the science in order, i just know
what works.
observation.
i have a 45 cube flat top.
mostly fires in 12 hours.
the theory is:
crystals grow best at 1900F.
and holding at that temp seem to develop the glaze.
same for reds/ they need that slow cool through the
1800F temp.
so, going up and down will sure change things.
carol marians has really done some work in electrics.
hank can fill us in again on his theories.
i just know it works.
in the old kilns/hard brick, the cooling was for days.
now, with these soft kilns they cool too fast.
many read old books and have no idea what modern kilns
are doing.
so.
just theories.
but, it works.
mel
from: minnetonka, mn
website: http://www.visi.com/~melpots/
clayart link: http://www.visi.com/~melpots/clayart.html
new book: http://www.21stcenturykilns.com
Jess McKenzie on sun 18 oct 09
I learned this in organic quant: Once you get above the
melting point of a compound--doesn't matter whether organic or
inorganic--the slower you reduce the temp, the bigger the
crystals get. I suspect this is related to the appearance of
the glaze: light diffraction (i.e., color) is surely
controlled by crystal size. For some compounds anyway.
~jess
....................
here are some simple answers.
i sure do not have all the science in order, i just know
what works.
observation.
i have a 45 cube flat top.
mostly fires in 12 hours.
the theory is:
crystals grow best at 1900F.
and holding at that temp seem to develop the glaze.
same for reds/ they need that slow cool through the
1800F temp.
so, going up and down will sure change things.
carol marians has really done some work in electrics.
hank can fill us in again on his theories.
i just know it works.
in the old kilns/hard brick, the cooling was for days.
now, with these soft kilns they cool too fast.
many read old books and have no idea what modern kilns
are doing.
so.
just theories.
but, it works.
mel
from: minnetonka, mn
website: http://www.visi.com/~melpots/
clayart link: http://www.visi.com/~melpots/clayart.html
new book: http://www.21stcenturykilns.com
Jess McKenzie on sun 18 oct 09
My apologies for the oversimplification. Melting point is
certainly a factor, but so is solubility. Briefly: Dissolve
a substance in a hot solvent, the reduce the temp slowly.
As the solvent's temp is reduced, the solubility of the
dissolved compound is decreased, and, for pure compounds,
crystals begin to form. If we drop the temp slow enough, the
crystals will grow larger. A good example is making rock
candy--dissolve sugar in almost-boiling water, then lower the
temp slowly, to develop really big crystals. Diffraction
characteristics, including color, are a function of crystal
size. We're speaking of microscopic crystals, of
course....~jess
I learned this in organic quant: Once you get above the
melting point of a compound--doesn't matter whether organic or
inorganic--the slower you reduce the temp, the bigger the
crystals get. I suspect this is related to the appearance of
the glaze: light diffraction (i.e., color) is surely
controlled by crystal size. For some compounds anyway.
~jess
....................
here are some simple answers.
i sure do not have all the science in order, i just know
what works.
observation.
i have a 45 cube flat top.
mostly fires in 12 hours.
the theory is:
crystals grow best at 1900F.
and holding at that temp seem to develop the glaze.
same for reds/ they need that slow cool through the
1800F temp.
so, going up and down will sure change things.
carol marians has really done some work in electrics.
hank can fill us in again on his theories.
i just know it works.
in the old kilns/hard brick, the cooling was for days.
now, with these soft kilns they cool too fast.
many read old books and have no idea what modern kilns
are doing.
so.
just theories.
but, it works.
mel
from: minnetonka, mn
website: http://www.visi.com/~melpots/
clayart link: http://www.visi.com/~melpots/clayart.html
new book: http://www.21stcenturykilns.com
Ron Roy on sat 31 oct 09
In other words - if any crystals did form on the way up they would be melte=
d
as the glaze reached maturity - so only slowing down the cooling will work
and only between certain temperatures.
RR
On Mon, Oct 19, 2009 at 8:06 PM, Des & Jan Howard wrot=
e:
> Rikki
> Downfiring means the soak is on the way 'down'.
> Soaking on the way up or at peak may help burn out
> organics, equalise kiln temp &/or heat work, but I
> doubt if anything else useful occurs.
> Des
>
>
> Rikki Gill wrote:
>
>> I have a question. What if I just decreased the gas pressure
>> when my kiln reached 1900 f. and stalled it for two hours?
>> I am a bit timid about changing what works pretty well for me now,
>> [okay, I'm a coward,] while I am doing my holiday production.
>> I will try your way next winter, but for now, I wonder if that would
>> do anything to enhance my pots?
>>
>> And why would it matter, or not matter, if it is the length
>> of time at a certain temp that creates the crystalline effect,
>> unless going to the higher temp somehow destroys it?
>>
>
> --
> Des & Jan Howard
> Lue Pottery
> Lue NSW
> Australia
> 2850
>
> 02 6373 6419
> www.luepottery.hwy.com.au
> -32.656072 149.840624
>
--
Ron Roy
15084 Little Lake Road
Brighton, Ontario, Canada
K0K 1H0
Steve Slatin on sun 1 nov 09
One thing to add here is that some things have an optimal
temperature for nucleation that is lower than their=3D20
optimal temperature from crystalline growth. The 'best'
way to grow these crystals is to drop to the optimal
nucleation temperature, hold, then rise to the optimal=3D20
growth temp, hold again, and then cool.
One of the reasons for the popularity of striking
iron glazes in a second firing is that it does this,
though of course it does so with a complete cool down
in the middle, which maximizes firing costs and the
risk of second-fire loss.
Steve Slatin --=3D20
--- On Sat, 10/31/09, Ron Roy wrote:
> In other words - if any crystals did
> form on the way up they would be melted
> as the glaze reached maturity - so only slowing down the
> cooling will work
> and only between certain temperatures.
>=3D20
> RR
>=3D20
> On Mon, Oct 19, 2009 at 8:06 PM, Des & Jan Howard
> wrote:
>=3D20
> > Rikki
> > Downfiring means the soak is on the way 'down'.
> > Soaking on the way up or at peak may help burn out
> > organics, equalise kiln temp &/or heat work, but
> I
> > doubt if anything else useful occurs.
> > Des
> >
> >
> > Rikki Gill wrote:
> >
> >> I have a question.=3DA0 What if I just decreased
> the gas pressure
> >> when my kiln reached 1900 f. and stalled it for
> two hours?
> >> I am a bit timid about changing what works pretty
> well for me now,
> >> [okay, I'm a coward,] while I am doing my holiday
> production.
> >> I will try your way next winter, but for now, I
> wonder if that would
> >> do anything to enhance my pots?
> >>
> >> And why would it matter, or not matter, if it is
> the length
> >> of time at a certain temp that creates the
> crystalline effect,
> >> unless going to the higher temp somehow destroys
> it?
> >>
> >
> > --
> > Des & Jan Howard
> > Lue Pottery
> > Lue=3DA0 NSW
> > Australia
> > 2850
> >
> > 02 6373 6419
> > www.luepottery.hwy.com.au
> > -32.656072 149.840624
> >
>=3D20
>=3D20
>=3D20
> --
> Ron Roy
> 15084 Little Lake Road
> Brighton, Ontario, Canada
> K0K 1H0
> =3D0A=3D0A=3D0A
Ron Roy on fri 6 nov 09
Hi agin Steve - Just read this and it answered my question - I'm working
backwards on the list today - way it is these days.
RR
On Sun, Nov 1, 2009 at 10:54 AM, Steve Slatin wrote=
:
> One thing to add here is that some things have an optimal
> temperature for nucleation that is lower than their
> optimal temperature from crystalline growth. The 'best'
> way to grow these crystals is to drop to the optimal
> nucleation temperature, hold, then rise to the optimal
> growth temp, hold again, and then cool.
>
> One of the reasons for the popularity of striking
> iron glazes in a second firing is that it does this,
> though of course it does so with a complete cool down
> in the middle, which maximizes firing costs and the
> risk of second-fire loss.
>
>
> Steve Slatin --
>
>
>
> --- On Sat, 10/31/09, Ron Roy wrote:
>
> > In other words - if any crystals did
> > form on the way up they would be melted
> > as the glaze reached maturity - so only slowing down the
> > cooling will work
> > and only between certain temperatures.
> >
> > RR
> >
> > On Mon, Oct 19, 2009 at 8:06 PM, Des & Jan Howard
> > wrote:
> >
> > > Rikki
> > > Downfiring means the soak is on the way 'down'.
> > > Soaking on the way up or at peak may help burn out
> > > organics, equalise kiln temp &/or heat work, but
> > I
> > > doubt if anything else useful occurs.
> > > Des
> > >
> > >
> > > Rikki Gill wrote:
> > >
> > >> I have a question. What if I just decreased
> > the gas pressure
> > >> when my kiln reached 1900 f. and stalled it for
> > two hours?
> > >> I am a bit timid about changing what works pretty
> > well for me now,
> > >> [okay, I'm a coward,] while I am doing my holiday
> > production.
> > >> I will try your way next winter, but for now, I
> > wonder if that would
> > >> do anything to enhance my pots?
> > >>
> > >> And why would it matter, or not matter, if it is
> > the length
> > >> of time at a certain temp that creates the
> > crystalline effect,
> > >> unless going to the higher temp somehow destroys
> > it?
> > >>
> > >
> > > --
> > > Des & Jan Howard
> > > Lue Pottery
> > > Lue NSW
> > > Australia
> > > 2850
> > >
> > > 02 6373 6419
> > > www.luepottery.hwy.com.au
> > > -32.656072 149.840624
> > >
> >
> >
> >
> > --
> > Ron Roy
> > 15084 Little Lake Road
> > Brighton, Ontario, Canada
> > K0K 1H0
> >
>
>
>
>
--
Ron Roy
15084 Little Lake Road
Brighton, Ontario, Canada
K0K 1H0
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