Gerholdclay on fri 13 jan 12
If your tiles are cracking one thing to try that has not been mentioned is =
t=3D
o compress the 4 sides. I have found this to be very helpful and do it on =
a=3D
ll big tiles. =3D20
Also be aware that many of the ideas suggested while improving cracking wil=
l=3D
also increase probability of warping- this seems particllarly true of firi=
n=3D
g on the edges. Underfiring the clay body reduces a lot of problems but do=
e=3D
sn't work well for outside applications.
Experimentation is the only real way to evaluate the tradeoffs for your cla=
y=3D
and applications. For myself since I can spend a lot of time on one piece=
a=3D
nd the clay cost is not really a factor I have found that a sculpture body =
m=3D
ade into paper clay cannot be equaled.
Paul
Sent from my iPad
On Jan 12, 2012, at 11:15 AM, Rimas VisGirda wrote:
> I've fired the triangles to cone 10, but at the moment can't remember why=
I=3D
would do that... Mostly I use them on larger plates and slabs that I do se=
c=3D
ondary firings to 05 and/or 018-012. I need to test a c/10 glaze I just mix=
e=3D
d so will throw in some triangles to the firing and let you know if they ar=
e=3D
OK in a few days.
>=3D20
> Not sure what you mean by slumping, the triangles lie flat on the kiln sh=
e=3D
lf. If you mean the clay object slumping around the triangles, my work is n=
o=3D
t super thin. For round pieces I put 3 triangles radially out from the cent=
e=3D
r; if it's a very wide plate I put 6 or 8 triangle under the foot rim also =
p=3D
ositioned radially outward. For rectilinear slabs, I just space them around=
u=3D
nder the slab...
>=3D20
> I also use the triangles when I fire gold luster on the inside of cylindr=
i=3D
cal pieces, vases, teabowls, yunomis, etc. I've found that if the work is d=
i=3D
rectly on the shelf the gold on the bottom comes out with bare spots. I thi=
n=3D
k that may be because the bottom stays cooler (longer to heat) than the sid=
e=3D
s and when it does get there it boils the vehicle out of the luster to gene=
r=3D
ate bare spots. Lusters should be dry when fired but a coating of luster is=
h=3D
ard to dry at the inside of a cylinder and I think the luster is not quite =
d=3D
ry when it gets to the temperature where the resin starts to react. Raising=
t=3D
he work off of the shelf has solved that problem, I think by allowing the b=
o=3D
ttom to heat up and dry the luster inside.
>=3D20
> -Rimas
> ________________________________
> From: Personal Gmail
>=3D20
> Rimas thanks for the tip about the triangles. The ones I saw for sale wi=
t=3D
h you link say to fire 04 maximum. Do you fire higher than that with them =
a=3D
nd do you have any problem with slumping? Thx, mJ
>=3D20
> Sent from my iPhone
>=3D20
> On Jan 10, 2012, at 7:05 AM, Rimas VisGirda wrote:
>=3D20
>> I multifire most of my work and have had larger tiles, over 10x10 inches=
o=3D
r so, crack. I have surmised that it typically occurs at quartz inversion, =
1=3D
063.4 F. I like to fire fast. I like to first-fire my terra cotta to around=
c=3D
one 3 as the color gets a nice rich orange; my stoneware and porcelain is f=
i=3D
rst bisque fired to cone 05 then to cone 10-11. My subsequent firings are t=
o=3D
cone 05 when deemed necessary and then to cone 018-012 as many times as ne=
e=3D
ded. I treat the terra cotta slightly differently from the stoneware/porcel=
a=3D
in. My kilns are vented and computer driven.
>>=3D20
>> I slow at quartz inversion, only if I have large
>> plates or tiles in the kiln, I have also started to lift the tiles and
>> plates off of the shelf with stilts or triangles.
>>=3D20
>> For porcelain/stoneware I bisque to cone 05, fast up fast down; then fas=
t=3D
up to cone 10 and slow the cooling down at quartz inversion. I ramp 25F/hr=
f=3D
rom 1075 to 1055. For successive firings I will slow at quartz inversion go=
i=3D
ng up as well as coming down, same ramp.
>>=3D20
>>=3D20
>> For terra cotta the first firing from greenware is cone 3 which in a sen=
s=3D
e is also the bisque firing, so I up fast and slow the cooling at quartz in=
v=3D
ersion, then successive firings are slowed at quartz inversion up and down =
a=3D
s for stoneware/porcelain.
>>=3D20
>> Regards, -Rimas
stephani stephenson on sat 14 jan 12
=3D20
Paul wrote:
.." many of the ideas suggested while=3D20
improving cracking will also increase probability of warping-=3D20
this seems particularly true of firing on the edges. "
Paul , that has not been true at all in my experience. I have noticed
no increase in warping as a result of firing tiles on edge .=3D20
none whatsoever,
the only similar thing I could envision where it would be an issue
=3DA0would be if you were firing a very thin slab or tile with a claybody =
yo=3D
u=3D20
were firing to the point where it began to vitrify and slump, and had no=
=3D
=3D20
side support.=3D20
my tiles are generally 1/2 to 5/8 inch thick, sometimes as thin=3D20
as 3/8 inch and fire easily without warping or cracking on end.=3D20
even large tiles.=3D20
In my experience the seeds for warping are sown in the forming process
whenever you introduce a differential in compression and tension .=3D20
For example ,you mention compressing the edges of a tile.=3D20
that's a good idea, just like compressing the rim of a wheel thrown bowl or=
=3D
plate.=3D20
and when you do that you basically strive for even compression all around.
When pressing a tile you also want to strive not only for compression=3D20
but for even compression over the entire surface area of the tile.
Warping can result when , for example , you compress the tile=3D20
pretty evenly across half it's length, but then end up stretching=3D20
the clay, ( putting it under tension), in order to get it to fill
=3DA0the entire mold.Or maybe your mind wanders and you just don't=3D20
compress as much on one side of the tile as you do the other.
=3DA0or it can result if you cut tiles from
plugs of clay that are more compressed on one end and more stretched on th=
=3D
e other.
Where the clay is subject to uneven and increased tension, it may tend to=
=3D
crack.
Where it is subject to uneven and increased compresion ,it may tend to war=
=3D
p. It will probably show=3D20
up in drying . You may have a chance to right it if you catch it and before=
=3D
it gets too hard. or sometimes=3D20
the warping won't show up til firing.=3D20
A forgiving clay body, such as the paperclay you use, or the body with a go=
=3D
od dollop of grog that=3D20
I use, allows us more leeway in this area, but if there are problems with w=
=3D
arping, look to either the drying or
the forming process, not so much the firing. that's my observation anyway.=
=3D
=3D20
for me, firing on end also allows me to fit a lot more tile=3D20
in each kiln load, using less shelving .( I don't use tile
setters)
cheers !
Stephani
Gerholdclay on sun 15 jan 12
Increased warping from firing tiles on their side has been my experience us=
i=3D
ng pretty consistant forming techniques. That being said my tiles are 20 i=
n=3D
ches square, about three eights inch thick =3D20
and fired to about 2 percent absorption.=3D20
I have not tried firing the tiles made from Pclay on their side. I will do=
t=3D
he test since saving energy and being able to fire a lot of tiles at one ti=
m=3D
e would be a plus.
Paul
Sent from my iPad
On Jan 15, 2012, at 1:38 AM, stephani stephenson w=
r=3D
ote:
>=3D20
> Paul wrote:
> .." many of the ideas suggested while=3D20
> improving cracking will also increase probability of warping-=3D20
> this seems particularly true of firing on the edges. "
>=3D20
> Paul , that has not been true at all in my experience. I have noticed
> no increase in warping as a result of firing tiles on edge .=3D20
> none whatsoever,
> the only similar thing I could envision where it would be an issue
> would be if you were firing a very thin slab or tile with a claybody yo=
u=3D
=3D20
> were firing to the point where it began to vitrify and slump, and had n=
o=3D
=3D20
> side support.=3D20
> my tiles are generally 1/2 to 5/8 inch thick, sometimes as thin=3D20
> as 3/8 inch and fire easily without warping or cracking on end.=3D20
> even large tiles.=3D20
>=3D20
> In my experience the seeds for warping are sown in the forming process
> whenever you introduce a differential in compression and tension .=3D20
> For example ,you mention compressing the edges of a tile.=3D20
> that's a good idea, just like compressing the rim of a wheel thrown bowl =
o=3D
r plate.=3D20
> and when you do that you basically strive for even compression all around=
.=3D
> When pressing a tile you also want to strive not only for compression=3D2=
0
> but for even compression over the entire surface area of the tile.
> Warping can result when , for example , you compress the tile=3D20
> pretty evenly across half it's length, but then end up stretching=3D20
> the clay, ( putting it under tension), in order to get it to fill
> the entire mold.Or maybe your mind wanders and you just don't=3D20
> compress as much on one side of the tile as you do the other.
> or it can result if you cut tiles from
> plugs of clay that are more compressed on one end and more stretched on =
t=3D
he other.
>=3D20
> Where the clay is subject to uneven and increased tension, it may tend =
t=3D
o crack.
> Where it is subject to uneven and increased compresion ,it may tend to w=
a=3D
rp. It will probably show=3D20
> up in drying . You may have a chance to right it if you catch it and befo=
r=3D
e it gets too hard. or sometimes=3D20
> the warping won't show up til firing.=3D20
> A forgiving clay body, such as the paperclay you use, or the body with a =
g=3D
ood dollop of grog that=3D20
> I use, allows us more leeway in this area, but if there are problems with=
w=3D
arping, look to either the drying or
> the forming process, not so much the firing. that's my observation anyway=
.=3D
=3D20
> for me, firing on end also allows me to fit a lot more tile=3D20
> in each kiln load, using less shelving .( I don't use tile
> setters)
> cheers !
> Stephani
stephani stephenson on sun 15 jan 12
HI Paul, I totally trust what you are saying regarding your tiles,(quoted b=
=3D
elow).
The fact that your tiles are thin, large and w/low=3DA0 absorption indicate=
s =3D
this.
=3DA0You have learned how to work with your clay , your dimensions, etc.You=
m=3D
ight be pushing that clay to it's limits and I'm sure=3DA0 they are well co=
ns=3D
tructed.=3DA0 And that's exactly how it should be.
Of all the questions throughout the years regarding tile, the most common o=
=3D
nes by far involve warping and cracking. Over and over again, that's where =
=3D
people have problems.
I guess my crusade has been that if someone is having consistent problems ,=
=3D
or is going through excessive time consuming rituals=3DA0 in drying and fir=
in=3D
g a tile=3DA0 ,they need to look at their claybody and also issues in formi=
ng=3D
and other factors such as=3DA0 thickness,=3D0A etc.
Many people start out trying to make a tile that looks like a commercial ti=
=3D
le, often 1/4 inch thick. commercial tiles are made from dry pressed clay t=
=3D
hat never had water in it from the beginning, so that is the wrong hare to =
=3D
chase, IMHO.
If you look at tiles from the craftsman era, for example, which were made f=
=3D
rom wet clay, you'll see they are thicker,=3DA0 and have clay bodies which =
ha=3D
ve grog in them (pulp, fiber would do the same thing).
It's a lovely thing when you can press tiles=3DA0 and then let them dry and=
f=3D
ire without having to worry that they are going to warp and crack . I also =
=3D
make quite large tiles. I dry them on their sides as well as bisque fire th=
=3D
em that way.
Occasionally I make tiles that need to be thinner or need to be made with a=
=3D
smoother clay fired to a higher temp. i take more care in the intial dryin=
=3D
g and will even stack=3DA0 field tiles verically and weight them till they =
go=3D
from moist leather hard to=3D0A dryer=3DA0 leather hard, before I turn the=
m on=3D
end. i still bisque them on end.=3D20
Glazed tile ,of course, i don't fire on end.
I understand people will want to push the envelope for aesthetic reasons, b=
=3D
ut if you make=3DA0 bales of tile like I do, , fussing with stuff you don't=
h=3D
ave to fuss with doesn't make sense. I'd rather spend time on making new de=
=3D
signs or handbuilding.
Yet what you say reminds us all=3DA0 that they need to test their own metho=
ds=3D
always.=3DA0=3D20
Just try to find a claybody that best suit your needs and=3DA0 listen to wh=
at=3D
the clay is telling you.=3D20
regards !
Stephani
"Increased warping from firing tiles on their side has been my experience=
=3D
=3D0A using pretty consistant forming techniques.=3DA0 That being said my t=
iles=3D
=3D0Aare 20 inches square, about three eights inch thick=3DA0 and fired to=
abo=3D
ut 2 percent absorption. "
-
stephani stephenson on sun 15 jan 12
I noticed that , in her haste, smart cookie left a few crumbs in the last p=
=3D
ost:
=3DA0i said I ," will even stack=3DA0 field tiles =3D0Avertically and weigh=
t them=3D
till they go from moist leather hard to=3D0A dryer=3DA0 leather hard, befo=
re I=3D
turn them on end. "
What I meant to say is that if I am using a finer bodied clay,=3DA0 I take =
fi=3D
eld tiles that are starting to stiffen, not wet but=3DA0 still flexible and=
m=3D
ake a vertical stack with horizontal tiles, and place a weight on the stack=
=3D
. paper can be placed between=3DA0 the tiles. Relief tiles of course, can't=
b=3D
e stacked if the relief is protruding.=3D20
with my coarser clays, i don't need to do this, i let them stiffen up on ha=
=3D
rdibacker=3DA0 or plaster board , and as soon as they can hold their own sh=
ap=3D
e, i stack them on end, like slices of bread in a loaf, compress the loaf=
=3D
=3DA0 a bit on each end with a brick., and leave them til they are dry.
hasty cookie,
Stephani
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