Lisa E on tue 30 jan 07
> This is probably a silly question but one I have to know.
>
> Other than temperature and saving on electrical costs, what is the
> difference between ^6 and ^10?
>
> I realize recipes have to be different based on the temperature and I am
> aware of how oxidation versus reduction affects glazes BUT what is the
> difference between choosing to fire at ^6 versus ^10?
>
> One of my pottery friends says it is easier to get the results she wants
> at ^10. But maybe that is because she has so much experience at ^10?!?!
>
> Due to the fact that the pot/glaze is fired at a hotter temperature, is
> the piece stronger and less inclined for breakage and chipping?
>
> Thank you in advance!
>
> Lisa
> --
> Lisa E
> Sunny Daze Design Pottery Studio
> SunnyDazeDesign@gmail.com
> Squamish, BC Canada
>
>
--
Lisa E
Sunny Daze Design Pottery Studio
SunnyDazeDesign@gmail.com
Squamish, BC Canada
www.lisaelbertsen.com http://picasaweb.google.com/SunnyDazeDesign
Snail Scott on wed 31 jan 07
At 08:24 AM 1/30/2007 -0800, you wrote:
>> Other than temperature and saving on electrical costs, what is the
>> difference between ^6 and ^10?
>> One of my pottery friends says it is easier to get the results she wants
>> at ^10. But maybe that is because she has so much experience at ^10?!?!
Some of the differences that people ascribe
to ^10 versus ^6 is actually one of atmosphere.
Most people who fire ^6 do so in electric
kilns, in an oxidizing atmosphere, while ^10
is more likely to occur in a gas kiln, in
reduction. Additionally, since gas kilns are
generally built thicker than electric ones,
the cooling times are significantly slowed.
For these reasons, it can be like comparing
apples and oranges. You have to be careful
to isolate the differences which are due to
temperature alone.
One reason for choosing ^10 is that many
more materials will melt at that temperature,
so there are more choices when creating a
glaze formula. At ^6, the choice of fluxes
is more limited. Nowadays, there are many
manufactured frits to serve this role,
however, not just natural feldspars and
boron minerals, so this discrepancy is much
less than it was just a few decades ago.
An advantage to ^6 is that although fewer
materials are available as fluxes, more
materials are available as colorants,
including stains that can burn out at ^10.
Of course, some colors need temperatures
even lower than ^6; that's a big reason
for the continued popularity of earthenware.
Recent innovations in stain manufacture
have made this less of an issue than
previously, too, although the new
encapsulated stains are somewhat expensive.
Wear and tear on kiln elements (if you are
assuming an electrical firing in either case)
is a genuine factor. Even electric kilns
rated for ^10 will need new elements much
sooner if fired to ^10 often instead of to
lower temperatures. It's a fairly big
difference. If you do heavy work, you will
also risk eventually warping shelves at ^10,
while they would be less affected at ^6.
A ^6 firing will also take less time, and
if you intend to monitor your firings
personally, it will be easier to make the
timing work out so you needn't stay up
late to shut it off.
>> Due to the fact that the pot/glaze is fired at a hotter temperature, is
>> the piece stronger and less inclined for breakage and chipping?
In principle, clay fired at ^10 can be
harder and more durable than at ^6, but
this assumes an optimally-formulated body
fired to the optimum level of vitrification.
In the real world, I suspect the difference
is somewhat reduced, and a bigger distinction
lies in how well a particular body suits its
temperature. An appropriately fired clay at
any temperature will be stronger than one
that's not properly vitrified. So, it's
possible but not necessarily the case for
every ^10-fired object; just for the ones
done right. How much stronger? Not a lot, I
believe, but some. The glaze/clay interface
is nearly always a bit better integrated,
and that creates more strength as well.
It's the clay body itself the matters most,
though. Some are stronger than other, and
many well-designed ^6 ones are stronger
than many ^10 ones, even with optimum
firing for each. In this case, the specific
circumstances trump broad generalities.
For me, the element wear-and-tear has been
a major factor in deciding to fire lower
in electric kilns. I originally switched
to mid-range stoneware (^4 at the time)
when I was doing gas firings, though. It
is easier to build a kiln that will reach
lower temperatures, and to do it with more
types of brick. The length-of-firing issue
was not a huge one, but after many nights
of nursing not-quite-well-designed kilns
through those last three or four cones of
heat-work until the wee hours of the
morning, the knowledge that I could have
been home in bed by midnight if I'd only
been aiming for ^5 was cause for thought.
Not every kiln is an ill-designed, leaky,
badly maintained beast with inadequate
burners and air, but life is easier if you
don't require high performance of every
machine you use.
My work is not functional pottery, either.
I believe that many potters prefer the
higher temperatures for the sake of the
incremental improvement in strength, which
is less relevant in work which is handled
less. More potters, though, seem to stick
with it for reasons of tradition, dating
to the day when only a higher temperature
firing would allow good melting of varied
glaze materials. It's what they learned,
and they've stuck with it. Nothing wrong
with tradition, but reevaluation is good,
too.
-Snail
>>
>>
>> Thank you in advance!
>>
>> Lisa
>> --
>> Lisa E
>> Sunny Daze Design Pottery Studio
>> SunnyDazeDesign@gmail.com
>> Squamish, BC Canada
>>
>>
>
>
>
>--
>Lisa E
>Sunny Daze Design Pottery Studio
>SunnyDazeDesign@gmail.com
>Squamish, BC Canada
>
>www.lisaelbertsen.com http://picasaweb.google.com/SunnyDazeDesign
>
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The Fuzzy Chef on wed 31 jan 07
Snail,
> An advantage to ^6 is that although fewer
> materials are available as fluxes, more
> materials are available as colorants,
> including stains that can burn out at ^10.
> Of course, some colors need temperatures
> even lower than ^6; that's a big reason
> for the continued popularity of earthenware.
> Recent innovations in stain manufacture
> have made this less of an issue than
> previously, too, although the new
> encapsulated stains are somewhat expensive.
Are there colorants other than stains available at cone 6 I should know
about?
>
> Wear and tear on kiln elements (if you are
> assuming an electrical firing in either case)
> is a genuine factor. Even electric kilns
> rated for ^10 will need new elements much
> sooner if fired to ^10 often instead of to
> lower temperatures. It's a fairly big
> difference. If you do heavy work, you will
> also risk eventually warping shelves at ^10,
> while they would be less affected at ^6.
This is a big issue. I used to have a decommissioned light industrial
kiln from Paragon, and pretty much had to replace the elements every
12-15 glaze firings. At $300 per set, that's no small issue.
The shelf warping issue is easily solved by buying 3/4" shelves.
However, those do cut space in the kiln, strain your back and make it
slower to heat.
--Josh Berkus
Ron Roy on fri 2 feb 07
Hi Lisa,
I think you can make perfectly good pottery at both temperatures - much
depends on the skill of the potter because making durable pots depends a
lot on how much the potter understands about their craft.
A well fitting glaze on a properly fired clay body at cone 6 is superior to
a badly fitting glaze on a poorly fired clay at cone 10 and visa versa.
When John and I wrote our book on cone 6 glazes - when we showed some
potters our glazes - they could not believe they were not cone 10 reduced
glazes. Slow cooling was the reason those glazes did not look like typical
cone 6 glazes. Part of the reason that cone 10 glazes look like they do is
because they usually cool slower in a gas kiln - compared to a small
electric kiln.
I fire at cone 10 reduction and the main difference is clay colour - I
prefer the way some clays look at cone 10 reduction. But I am not saying my
work is superior to anyone who works at cone 6 - in fact I will go so far
as to say it is easier to solve the technical issues at cone 6 because of
what reduction can do to some clay bodies.
RR
>> This is probably a silly question but one I have to know.
>>
>> Other than temperature and saving on electrical costs, what is the
>> difference between ^6 and ^10?
>>
>> I realize recipes have to be different based on the temperature and I am
>> aware of how oxidation versus reduction affects glazes BUT what is the
>> difference between choosing to fire at ^6 versus ^10?
>>
>> One of my pottery friends says it is easier to get the results she wants
>> at ^10. But maybe that is because she has so much experience at ^10?!?!
>>
>> Due to the fact that the pot/glaze is fired at a hotter temperature, is
>> the piece stronger and less inclined for breakage and chipping?
>>
>> Thank you in advance!
>>
>> Lisa
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
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