plasterjfl@AOL.COM on wed 4 jan 12
Interesting suggestion David. Thank you.
I've done the "little balls rolled in alumina" trick before, when I fired a
salt/wood kiln with Craig Edwards (years ago) but I didn't think that
would necessarily apply to cone 6 porcelain in an electric kiln.
I see your point about the cookie technique though.
Looks like I have some experimentation in front of me.
take care
Jeff
plasterjfl@AOL.COM on wed 4 jan 12
A question for those who may know: does anyone know how the ancient potters
made thin porcelain pots with thin porcelain foot rims without having the
foot rim deform in anyway?
I slip cast. My plates are cast upside down such that the sprew hole, as it
were, becomes the foot rim when I separate the two mold halves. The wall
of a slip cast pot is thin. Consequently the foot rim of my plates are thi=
n
as well. For this reason the feet of my porcelain plates deform to various
degrees. I'd like to eliminate this deformation.
I know we've talked about adding alumina hydrate to wax resist but is that
really the solution? The foot rim still slides along the surface of the
rough kiln shelf does it not?
I've wondered if the ancients fired their pots on porcelain cookies
instead. (i.e. a thin porcelain disc that shrinks along with the porcelain =
piece
so deformation is prevented.)
Suggestions would be appreciated.
Thanks
Jeff Longtin
Minneapolis
_www.jefflongtin.etsy.com_ (http://www.jefflongtin.etsy.com)
Steve Mills on wed 4 jan 12
Jeff,
You've just answered your own question.=3D20
At college all pots were fired on "cookies" (we know them as "Setters"), pa=
r=3D
tly to prevent warping, but also so that they released easily from the shel=
f=3D
, and where a glaze might run off the foot. That's how I use them.=3D20
Steve M
Steve Mills
Bath
UK
Sent from my iPod
On 4 Jan 2012, at 18:03, plasterjfl@AOL.COM wrote:
?
>=3D20
> I've wondered if the ancients fired their pots on porcelain cookies
> instead. (i.e. a thin porcelain disc that shrinks along with the porcelai=
n=3D
piece
> so deformation is prevented.)
>=3D20
> Suggestions would be appreciated.
>=3D20
> Thanks
>=3D20
> Jeff Longtin
> Minneapolis
> _www.jefflongtin.etsy.com_ (http://www.jefflongtin.etsy.com)
David Woof on wed 4 jan 12
Hi Jeff=3D2C
I fire all my plates=3D2C platters and wide bottom anything=3D2C footed or =
othe=3D
rwise=3D2C on (epk=3D2C alumina=3D2C and sawdust) balls=3D2C Elmers glued t=
o the fe=3D
et as they are loaded to accommodate rough and irregular or warped shelves =
=3D
etc. Try to center straddle two=3D2C even new=3D2C half shelves with a larg=
e fo=3D
ot rim on a kiln filling platter!!!=3DA0 Self leveling when fresh=3D2C and =
with=3D
enough roll/give to accommodate the shrinkage without drag.=3DA0 Wood=3D2C=
Gas=3D
=3D2C Electric=3D2C...all the same to me.
As I'm sure you know=3D2C at vitrification=3D2C the vessel is also pyroplas=
tic =3D
enough to cause it to deform on the uneven shelf=3D2C so friction drag from=
s=3D
hrinkage is not your only issue or cause of warping and cracking.
Added very important bonus from using the balls is that heat is allowed to =
=3D
convect/radiate under the ware for more even heating and cooling. Thus no c=
=3D
racked or warped rims and bottoms.=3D20
When large ware sits directly on the shelf and heating is "rapid=3D2C" the =
ar=3D
ea under the base of a large vessel heats and cools at a different rate tha=
=3D
n sides and rim.
This causes many folks much frustration and wasters.
Put this accumulated waste over time=3D2C up against the time and effort of=
t=3D
his "extra" step in loading and it still comes out in the black for pots sa=
=3D
ved. Try if you will=3D2C and do your own math.
Trying to use sand as a rolling surface is such a mess to clean up with ris=
=3D
k of scratching your fine foot=3D2C and of sand getting into the ware next =
sh=3D
elves down!!!
Shrink pads usually warp a bit=3D2C so one must still use the balls to leve=
l =3D
the platter=3D2C and below the pad as well to level the shrink pad to the s=
he=3D
lf. Gets to be a time wasting cluster......!!!
Best for success=3D2C
David Woof
_______________________________________________________________
15. Thin porcelain foot rim
Posted by: "plasterjfl@AOL.COM" plasterjfl@AOL.COM=3D20
Date: Wed Jan 4=3D2C 2012 11:02 am ((PST))
=3D20
A question for those who may know: does anyone know how the ancient potters
made thin porcelain pots with thin porcelain foot rims without having the
foot rim deform in anyway?
=3D20
I slip cast. My plates are cast upside down such that the sprew hole=3D2C a=
s =3D
it
were=3D2C becomes the foot rim when I separate the two mold halves. The wa=
ll
of a slip cast pot is thin. Consequently the foot rim of my plates are thi=
=3D
n
as well. For this reason the feet of my porcelain plates deform to various
degrees. I'd like to eliminate this deformation.
=3D20
I know we've talked about adding alumina hydrate to wax resist but is that
really the solution? The foot rim still slides along the surface of the
rough kiln shelf does it not?
=3D20
I've wondered if the ancients fired their pots on porcelain cookies
instead. (i.e. a thin porcelain disc that shrinks along with the porcelain =
=3D
piece
so deformation is prevented.)
=3D20
Suggestions would be appreciated.
=3D20
Thanks
=3D20
Jeff Longtin
Minneapolis
_www.jefflongtin.etsy.com_ (http://www.jefflongtin.etsy.com)
=3D
David Woof on thu 5 jan 12
Hi Jeff=3D2C everyone=3D2C
Not to discredit the usefulness of=3D3B "cookies" A.K.A "shrink pads" "sett=
er=3D
s" etc.=3DA0 I use them also where appropriate for application in my work. =
I =3D
find them especially good for vessels with four delicate "pedestal" feet.=
=3D
=3DA0=3D20
Again as I said below=3D3B I layer the pad between balls on feet to pad=3D2=
C an=3D
d balls on underside of pad to shelf.=3DA0 Luxury ride/glide for the vessel=
.
And Jeff=3D2C I'm sure you don't under estimate cone 6 as a temp for deform=
at=3D
ion which root cause is due to pyroplasticity.=3DA0 For cone 10 stoneware=
=3D3B =3D
cone 6 is where notable vitrification and thus shrinkage usually just begin=
=3D
s. On the other hand=3D2C Porcelain formulated to go translucent at cone 6 =
wo=3D
uld obviously be at maturation and thus susceptible to deformation and even=
=3D
cracking from friction drag and uneven shelf settings due to its pyroplast=
=3D
ic condition.
Also have you considered the possible differences between the compression d=
=3D
ensity and structural integrity of slip cast bodies vs. thrown ware?=3DA0 S=
om=3D
e rules apply to both=3D2C some may be different.
Good to refresh with new research when we are faced with solving a good hea=
=3D
d scratcher.=3D20
David Woof
____________________________________________
1c. Re: Thin porcelain foot rim
Posted by: "plasterjfl@AOL.COM" plasterjfl@AOL.COM=3D20
Date: Thu Jan 5=3D2C 2012 4:28 am ((PST))
=3D20
Interesting suggestion David. Thank you.
=3D20
I've done the "little balls rolled in alumina" trick before=3D2C when I fir=
ed=3D
a
salt/wood kiln with Craig Edwards (years ago) but I didn't think that
would necessarily apply to cone 6 porcelain in an electric kiln.
=3D20
I see your point about the cookie technique though.
=3D20
Looks like I have some experimentation in front of me.
=3D20
take care
=3D20
Jeff
__________________________________________________
1b. Re: Thin porcelain foot rim
Posted by: "David Woof" woofpots@HOTMAIL.COM=3D20
Date: Wed Jan 4=3D2C 2012 7:47 pm ((PST))
=3D20
Hi Jeff=3D2C
=3D20
I fire all my plates=3D2C platters and wide bottom anything=3D2C footed or =
othe=3D
rwise=3D2C on (epk=3D2C alumina=3D2C and sawdust) balls=3D2C Elmers glued t=
o the fe=3D
et as they are loaded to accommodate rough and irregular or warped shelves =
=3D
etc. Try to center straddle two=3D2C even new=3D2C half shelves with a larg=
e fo=3D
ot rim on a kiln filling platter!!!=3DA0 Self leveling when fresh=3D2C and =
with=3D
enough roll/give to accommodate the shrinkage without drag.=3DA0 Wood=3D2C=
Gas=3D
=3D2C Electric=3D2C...all the same to me.
=3D20
As I'm sure you know=3D2C at vitrification=3D2C the vessel is also pyroplas=
tic =3D
enough to cause it to deform on the uneven shelf=3D2C so friction drag from=
s=3D
hrinkage is not your only issue or cause of warping and cracking.
=3D20
Added very important bonus from using the balls is that heat is allowed to =
=3D
convect/radiate under the ware for more even heating and cooling. Thus no c=
=3D
racked or warped rims and bottoms.=3D20
=3D20
When large ware sits directly on the shelf and heating is "rapid=3D2C" the =
ar=3D
ea under the base of a large vessel heats and cools at a different rate tha=
=3D
n sides and rim.
This causes many folks much frustration and wasters.
=3D20
Put this accumulated waste over time=3D2C up against the time and effort of=
t=3D
his "extra" step in loading and it still comes out in the black for pots sa=
=3D
ved. Try if you will=3D2C and do your own math.
=3D20
Trying to use sand as a rolling surface is such a mess to clean up with ris=
=3D
k of scratching your fine foot=3D2C and of sand getting into the ware next =
sh=3D
elves down!!!
=3D20
Shrink pads usually warp a bit=3D2C so one must still use the balls to leve=
l =3D
the platter=3D2C and below the pad as well to level the shrink pad to the s=
he=3D
lf. Gets to be a time wasting cluster......!!!
=3D20
=3D20
Best for success=3D2C
=3D20
David Woof
_______________________________________________________________
=3D20
15. Thin porcelain foot rim
Posted by: "plasterjfl@AOL.COM" plasterjfl@AOL.COM=3D20
Date: Wed Jan 4=3D2C 2012 11:02 am ((PST))
=3D20
A question for those who may know: does anyone know how the ancient potters
made thin porcelain pots with thin porcelain foot rims without having the
foot rim deform in anyway?
=3D20
I slip cast. My plates are cast upside down such that the sprew hole=3D2C a=
s =3D
it
were=3D2C becomes the foot rim when I separate the two mold halves. The wa=
ll
of a slip cast pot is thin. Consequently the foot rim of my plates are thi=
=3D
n
as well. For this reason the feet of my porcelain plates deform to various
degrees. I'd like to eliminate this deformation.
=3D20
I know we've talked about adding alumina hydrate to wax resist but is that
really the solution? The foot rim still slides along the surface of the
rough kiln shelf does it not?
=3D20
I've wondered if the ancients fired their pots on porcelain cookies
instead. (i.e. a thin porcelain disc that shrinks along with the porcelain =
=3D
piece
so deformation is prevented.)
=3D20
Suggestions would be appreciated.
=3D20
Thanks
=3D20
Jeff Longtin
Minneapolis
_www.jefflongtin.etsy.com_ (http://www.jefflongtin.etsy.com)
________________________________________________________________________
=3D
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