sharonia628 on mon 9 jan 12
Hi all:
I've been making large address tiles (about 18"x 20"), earthenware, fired
to 04. The last two tiles cracked in the bisque. After some research I've
found my mistakes (the clay needs to have grog - duh, I should have known
this), and the firing should be slow cooled.
My question is: slow cooled to what temp? And how slow? I do have an
electronic controller, I can slow cool if need be, but I'd sort of like to
have more specific parameters.
Thanks all,
Sharon
--
Sharon La Rocca Miranda
www.sharonmiranda.com
stephani stephenson on mon 9 jan 12
Have you considered firing the tiles on end?=3DA0 stand them n end next to =
ea=3D
ch
other like pieces of bread in a loaf. If need be 'sandwich ' them between
two upright bricks or shelves backed bybricks to hold them nicely=3DA0 vert=
ic=3D
al.=3D20
I don't think you have to go abnormally=3DA0 slow in the cooldown, unless y=
ou
have a claybody that is prone to=3DA0 dunting=3DA0 in general....just don't=
go =3D
fast
with larger pieces! especially through quartz inversion or=3DA0 down from r=
ed
heat to about 200 - 400 degrees F. 200,(or stone cold if you really are
wanting to make sure)=3DA0 . my cooldowns=3DA0 are often from 12 -24 hours.=
but
seriously, try firing them on end. some claybodies=3DA0 which are fine for
smaller tiles=3DA0=3DA0 can be=3DA0 quite problematic when making tiles thi=
s size=3D
. If
firing on end doesn't solve the problem, adjusting the thickness or adding
grog or fiber or pulp might help.
Stephani Stephenson
Rimas VisGirda on tue 10 jan 12
I multifire most of my work and have had larger tiles, over 10x10 inches or=
so, crack. I have surmised that it typically occurs at quartz inversion, 1=
063.4 F. I like to fire fast. I like to first-fire my terra cotta to around=
cone 3 as the color gets a nice rich orange; my stoneware and porcelain is=
first bisque fired to cone 05 then to cone 10-11. My subsequent firings ar=
e to cone 05 when deemed necessary and then to cone 018-012 as many times a=
s needed. I treat the terra cotta slightly differently from the stoneware/p=
orcelain. My kilns are vented and computer driven.
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.
For porcelain/stoneware I bisque to cone 05, fast up fast down; then fast u=
p to cone 10 and slow the cooling down at quartz inversion. I ramp 25F/hr f=
rom 1075 to 1055. For successive firings I will slow at quartz inversion go=
ing up as well as coming down, same ramp.
For terra cotta the first firing from greenware is cone 3 which in a sense =
is also the bisque firing, so I up fast and slow the cooling at quartz inve=
rsion, then successive firings are slowed at quartz inversion up and down a=
s for stoneware/porcelain.
Regards, -Rimas
ronroy@CA.INTER.NET on tue 10 jan 12
Hi Sharon,
Kilns cool unevenly so you probably have to start your slow cool
earlier than you would think - I would suggest 700C (1300F) - slow to
50C (100F) till 500C (950F) that should work.
RR
Quoting sharonia628 :
> Hi all:
> I've been making large address tiles (about 18"x 20"), earthenware, fired
> to 04. The last two tiles cracked in the bisque. After some research I've
> found my mistakes (the clay needs to have grog - duh, I should have know=
n
> this), and the firing should be slow cooled.
>
> My question is: slow cooled to what temp? And how slow? I do have an
> electronic controller, I can slow cool if need be, but I'd sort of like t=
o
> have more specific parameters.
>
> Thanks all,
> Sharon
>
> --
> Sharon La Rocca Miranda
> www.sharonmiranda.com
>
ronroy@CA.INTER.NET on tue 10 jan 12
Hi Rimas,
Not sure when the cracking is happening and to what clays - If I can
see your clay recipes I might be able to help from that angle.
If it's happening to the high fire stoneware it could also be cristobalite.
Is it happening in a certain part of your kilns?
RR
Quoting Rimas VisGirda :
> I multifire most of my work and have had larger tiles, over 10x10
> inches or so, crack. I have surmised that it typically occurs at
> quartz inversion, 1063.4 F. I like to fire fast. I like to
> first-fire my terra cotta to around cone 3 as the color gets a nice
> rich orange; my stoneware and porcelain is first bisque fired to
> cone 05 then to cone 10-11. My subsequent firings are to cone 05
> when deemed necessary and then to cone 018-012 as many times as
> needed. I treat the terra cotta slightly differently from the
> stoneware/porcelain. My kilns are vented and computer driven.
>
> 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.
>
> For porcelain/stoneware I bisque to cone 05, fast up fast down; then
> fast up to cone 10 and slow the cooling down at quartz inversion. I
> ramp 25F/hr from 1075 to 1055. For successive firings I will slow at
> quartz inversion going up as well as coming down, same ramp.
>
>
> For terra cotta the first firing from greenware is cone 3 which in a
> sense is also the bisque firing, so I up fast and slow the cooling
> at quartz inversion, then successive firings are slowed at quartz
> inversion up and down as for stoneware/porcelain.
>
> Regards, -Rimas
>
Rimas VisGirda on tue 10 jan 12
Hi, I was replying to sharona628's post who was having problems with large =
tiles cracking. I've got my problem solved with the slow ramp past quartz i=
nversion and elevating the work when the clay is mature or vitrified. I use=
lots of different clays primarily high fire and only have multifiring prob=
lems with flat pieces, tiles and plates, that are wider than about 10 inche=
s; all other shapes and sizes take the many firings in stride. Some of my p=
ieces are fired 10-20 times... Thanks for your offer. Regards, -Rimas
________________________________
From: "ronroy@ca.inter.net"
To: Rimas VisGirda
Cc: Clayart@LSV.CERAMICS.ORG
Sent: Tuesday, January 10, 2012 11:31 AM
Subject: Re: large tiles cracking
Hi Rimas,
Not sure when the cracking is happening and to what clays - If I can see yo=
ur clay recipes I might be able to help from that angle.
If it's happening to the high fire stoneware it could also be cristobalite.
Is it happening in a certain part of your kilns?
RR
Quoting Rimas VisGirda :
> I multifire most of my work and have had larger tiles, over 10x10 inches =
or so, crack. I have surmised that it typically occurs at quartz inversion,=
1063.4 F. I like to fire fast. I like to first-fire my terra cotta to arou=
nd cone 3 as the color gets a nice rich orange; my stoneware and porcelain =
is first bisque fired to cone 05 then to cone 10-11. My subsequent firings =
are to cone 05 when deemed necessary and then to cone 018-012 as many times=
as needed. I treat the terra cotta slightly differently from the stoneware=
/porcelain. My kilns are vented and computer driven.
>
> 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.
>
> For porcelain/stoneware I bisque to cone 05, fast up fast down; then fast=
up to cone 10 and slow the cooling down at quartz inversion. I ramp 25F/hr=
from 1075 to 1055. For successive firings I will slow at quartz inversion =
going up as well as coming down, same ramp.
>
>
> For terra cotta the first firing from greenware is cone 3 which in a sens=
e is also the bisque firing, so I up fast and slow the cooling at quartz in=
version, then successive firings are slowed at quartz inversion up and down=
as for stoneware/porcelain.
>
> Regards, -Rimas
>
sharonia628 on tue 10 jan 12
Thanks for the good info about firing down. According to Ron Roy :
"Kilns cool unevenly so you probably have to start your slow cool earlier
than you would think - I would suggest 700C (1300F) - slow to 50C (100F)
till 500C (950F) that should work."
Others suggested grog on the shelves and firing the kiln full, as well as
firing the tiles on their edges. This last is not something I can do -
these are really big tiles, in odd shapes (see my website for examples).
BTW, I did find a good website with good info about this:
http://www.lakesidepottery.com/HTML%20Text/Tips/Making%20Ceramic%20Tiles.ht=
m
I'm now on my third attempt and biting my fingernails. But hopeful because
of all this good advice.
Thanks, guys!
Sharon
--
Sharon La Rocca Miranda
www.sharonmiranda.com
Personal Gmail on wed 11 jan 12
Rimas thanks for the tip about the triangles. The ones I saw for sale with=
y=3D
ou link say to fire 04 maximum. Do you fire higher than that with them and=
d=3D
o you have any problem with slumping? Thx, mJ
Sent from my iPhone
On Jan 10, 2012, at 7:05 AM, Rimas VisGirda wrote:
> 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 fast=
u=3D
p to cone 10 and slow the cooling down at quartz inversion. I ramp 25F/hr f=
r=3D
om 1075 to 1055. For successive firings I will slow at quartz inversion goi=
n=3D
g up as well as coming down, same ramp.
>=3D20
>=3D20
> For terra cotta the first firing from greenware is cone 3 which in a sens=
e=3D
is also the bisque firing, so I up fast and slow the cooling at quartz inv=
e=3D
rsion, then successive firings are slowed at quartz inversion up and down a=
s=3D
for stoneware/porcelain.
>=3D20
> Regards, -Rimas
Rimas VisGirda on wed 11 jan 12
Triangles are 3 sided sticks of clay. I first saw and got some at the Royal=
=3D
Copenhagen factory in Denmark, recently AMACO has started to carry a simil=
=3D
ar product. I also use their tile setters for firing commercial tile. -Rima=
=3D
s=3D0A=3D0Ahttp://www.amaco.com/shop/product-468-triangles.html=3D0Ahttp://=
www.am=3D
aco.com/shop/product-161-tile-plate-setters.html=3D0A=3D0A_________________=
____=3D
___________=3D0AFrom: Dan Bowman =3D0ATo: rtv1942@YAHOO=
.COM=3D
=3D0ASent: Wednesday, January 11, 2012 7:25 AM=3D0ASubject: re: large tile=
s cr=3D
acking=3D0A=3D0ARimas,=3D0AI appreciate your post as I am getting ready to =
fire s=3D
ome tiles. =3DA0Just curious, could you be more specific on what you mean b=
y =3D
"triangles" that you use to support the tiles?=3DA0=3D0A=3D0AThanks,=3D0A=
=3D0AAlice D=3D
eLisle=3D0A=3D0A919-210-5299=3D0Awanderland@att.net=3D0Ahttp://www.etsy.com=
/shop/Is=3D
landTextures=3D0Ahttp://www.flickr.com/photos/alice_delisle/
Lee on thu 12 jan 12
Rimas,
If your cracking is caused by quartz inversion, you might
consider crash cooling to 1100*C Slow cooling causes increased *
cristabolite* . It is the same phenomenon that MC6 uses to cause crystals
in glazes by holding temp.
Mick Casson found that crash cooling in high silica clay bodies
decreases the chance of dunting. It also helps create red color in
unglazed high alumina clay bodies in wood and soda firing.
One size does no fit all.
--
Lee Love in Minneapolis
http://mingeisota.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he land
of eternal youth is behind the house, a beautiful land fluent within
itself." -- John O'Donohue
Rimas VisGirda on thu 12 jan 12
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=
=3D
condary firings to 05 and/or 018-012. I need to test a c/10 glaze I just mi=
=3D
xed so will throw in some triangles to the firing and let you know if they =
=3D
are OK in a few days.=3D0A=3D0ANot sure what you mean by slumping, the tria=
ngle=3D
s lie flat on the kiln shelf. If you mean the clay object slumping around t=
=3D
he triangles, my work is not super thin. For round pieces I put 3 triangles=
=3D
radially out from the center; if it's a very wide plate I put 6 or 8 trian=
=3D
gle under the foot rim also positioned radially outward. For rectilinear sl=
=3D
abs, I just space them around under the slab...=3D0A=3D0AI also use the tri=
angl=3D
es when I fire gold luster on the inside of cylindrical pieces, vases, teab=
=3D
owls, yunomis, etc. I've found that if the work is directly on the shelf th=
=3D
e gold on the bottom comes out with bare spots. I think that may be because=
=3D
the bottom stays cooler (longer to heat) than the sides and when it does g=
=3D
et there it boils the vehicle out of the luster to generate bare spots. Lus=
=3D
ters should be dry when fired but a coating of luster is hard to dry at the=
=3D
inside of a cylinder and I think the luster is not quite dry when it gets =
=3D
to the temperature where the resin starts to react. Raising the work off of=
=3D
the shelf has solved that problem, I think by allowing the bottom to heat =
=3D
up and dry the luster inside.=3D0A=3D0A-Rimas=3D0A_________________________=
______=3D
_=3D0AFrom: Personal Gmail =3D0A=3D0ARimas thanks for=
the t=3D
ip about the triangles.=3DA0 The ones I saw for sale with you link say to f=
ir=3D
e 04 maximum.=3DA0 Do you fire higher than that with them and do you have a=
ny=3D
problem with slumping?=3DA0 Thx, mJ=3D0A=3D0ASent from my iPhone=3D0A=3D0A=
On Jan 10,=3D
2012, at 7:05 AM, Rimas VisGirda wrote:=3D0A=3D0A> I m=
ulti=3D
fire most of my work and have had larger tiles, over 10x10 inches or so, cr=
=3D
ack. I have surmised that it typically occurs at quartz inversion, 1063.4 F=
=3D
. I like to fire fast. I like to first-fire my terra cotta to around cone 3=
=3D
as the color gets a nice rich orange; my stoneware and porcelain is first =
=3D
bisque fired to cone 05 then to cone 10-11. My subsequent firings are to co=
=3D
ne 05 when deemed necessary and then to cone 018-012 as many times as neede=
=3D
d. I treat the terra cotta slightly differently from the stoneware/porcelai=
=3D
n. My kilns are vented and computer driven.=3D0A> =3D0A> I slow at quartz i=
nver=3D
sion, only if I have large=3D0A> plates or tiles in the kiln, I have also s=
ta=3D
rted to lift the tiles and=3D0A> plates off of the shelf with stilts or tri=
an=3D
gles.=3D0A> =3D0A> For porcelain/stoneware I bisque to cone 05, fast up fas=
t do=3D
wn; then fast up to cone 10 and slow the cooling down at quartz inversion. =
=3D
I ramp 25F/hr from 1075 to 1055. For successive firings I will slow at quar=
=3D
tz inversion going up as well as coming down, same ramp.=3D0A> =3D0A> =3D0A=
> For =3D
terra cotta the first firing from greenware is cone 3 which in a sense is a=
=3D
lso the bisque firing, so I up fast and slow the cooling at quartz inversio=
=3D
n, then successive firings are slowed at quartz inversion up and down as fo=
=3D
r stoneware/porcelain.=3D0A> =3D0A> Regards, -Rimas
Rimas VisGirda on thu 12 jan 12
Lee, you are not reading my posts, my original post was in response to some=
=3D
ones question. I laid out the parameters through which I fire then I indica=
=3D
ted I solved my problem and continued to illustrate how. And yes, one size =
=3D
does not fit all, I don't think I said it did. -Rimas=3D0A_________________=
__=3D
_____________=3D0AFrom: Lee =3D0A=3D0A=3DA0 =3DA0 =
=3DA0 =3DA0 =3DA0=3D
=3DA0 =3DA0If your cracking is caused by quartz inversion, you might consi=
der =3D
crash cooling to 1100*C =3DA0 =3DA0 Slow cooling causes increased=3DA0crist=
abolit=3D
e=3DA0. =3DA0 It is the same phenomenon that MC6 uses to cause crystals in =
glaz=3D
es by holding temp.=3D0A=3D0A=3DA0 =3DA0 =3DA0 =3DA0 =3DA0 =3DA0 Mick Casso=
n found that cra=3D
sh cooling in high silica clay bodies decreases the chance of dunting. =3DA=
0 =3D
=3DA0It also helps create red color in unglazed high alumina clay bodies in=
w=3D
ood and soda firing.=3D0A=3D0A=3DA0 =3DA0 =3DA0 =3DA0 =3DA0 One size does n=
o fit all.=3D0A-=3D
-=3D0A=3DA0Lee Love in Minneapolis
Lee on thu 12 jan 12
Rimas, I was writing for the original questioner. Below is for them too.
Also, multiple firings increase the chances of cristobalite formation.
Each time you fire, more crystals are formed in the clay. Crash
cooling can reduce this effect.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Eleanora Eden on thu 12 jan 12
Hi Sharon,
I noticed that Ron mentioned the placement in the kiln, just as I was
remembering his advice years ago to put large platters in the top half
of the kiln, as the bottom half tends to cool faster.
This advice helped me a whole lot.
Eleanora
>Hi all:
>I've been making large address tiles (about 18"x 20"), earthenware, fired
>to 04. The last two tiles cracked in the bisque. After some research I've
>found my mistakes (the clay needs to have grog - duh, I should have known
>this), and the firing should be slow cooled.
>
>My question is: slow cooled to what temp? And how slow? I do have an
>electronic controller, I can slow cool if need be, but I'd sort of like to
>have more specific parameters.
>
>Thanks all,
>Sharon
>
>--
>Sharon La Rocca Miranda
>www.sharonmiranda.com
--
Bellows Falls Vermont
www.eleanoraeden.com
Alice DeLisle on fri 13 jan 12
=3D46rom MJ: "Rimas thanks for the tip about the triangles. The ones I =
=3D
saw for sale with you link say to fire 04 maximum. "
The triangles from Amaco are rated to cone 10. See page 116 of their =3D
catalog. Some distributors carry them.
http://amacofiles.com/files/amaco-2011-fullcatalog-web.pdf
Alice DeLisle
wanderland@att.net
http://www.etsy.com/shop/IslandTextures
http://www.flickr.com/photos/alice_delisle/
Rimas VisGirda on fri 13 jan 12
Thanks Alice, the link I sent WAS from AMACO's website and now I see that i=
=3D
t says cone 04 there. I looked them up in my paper catalog and there they a=
=3D
re good for cone 10 (2009/p109). So it appears if you fire to cone 10 bette=
=3D
r not buy them online ;-)... I thought they were good to cone 10; I fired s=
=3D
ome yesterday but the kiln had an error code when I checked it (no cone bac=
=3D
k-up). I'll be firing again in a day or two and will put a cone in for refe=
=3D
rence.Regards, -Rimas=3D0A=3D0A=3D0A=3D0A----- Original Message -----=3D0AF=
rom: Alice=3D
DeLisle =3D0A=3D0AFrom MJ:=3DA0 "Rimas thanks for the =
tip ab=3D
out the triangles.=3DA0 The ones I saw for sale with you link say to fire 0=
4 =3D
maximum. "=3D0A=3D0AThe triangles from Amaco are rated to cone 10.=3DA0 See=
page =3D
116 of their catalog.=3DA0 Some distributors carry them.=3D0A=3D0Ahttp://am=
acofil=3D
es.com/files/amaco-2011-fullcatalog-web.pdf=3D0A=3D0AAlice DeLisle=3D0A=3D0=
Awanderl=3D
and@att.net=3D0Ahttp://www.etsy.com/shop/IslandTextures=3D0Ahttp://www.flic=
kr.c=3D
om/photos/alice_delisle/
stephani stephenson on sat 14 jan 12
Sharon, you don't mention how you are making your address tiles.=3D20
One other thing that could be contributing to cracking is increased=3DA0 an=
d =3D
uneven stretching of the clay=3DA0 when you are forming it.
=3DA0If the clay is under an uneven amount of tension in an area, (getting =
st=3D
reched around a form in one area and getting highly compressed in another f=
=3D
or example),=3DA0 cracks can show up at that place.=3DA0 some clays=3DA0 ha=
ve les=3D
s tolerance for variation than others when it comes to large slabs. thickne=
=3D
ss, amount of grog, etc=3DA0 are also factors when it comes to how precise =
yo=3D
u need to be in the forming process. just a thought, which may or may not a=
=3D
pply in your case, but thought it was worth a mention
cheers,
Stephani S.
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