John Miller on wed 25 feb 04
Hi All, After paper clay is fired and the paper fibers have burned out,
how can this be stronger than regular clay.
It would seem that the fibers that do make it stronger in dry form, but
the same with thousands of holes burned through it would weaken the body.
Enlighten me on this.
Thanks, John
Roly Beevor on wed 25 feb 04
John Miller wrote
> Hi All, After paper clay is fired and the paper fibers have burned out,
> how can this be stronger than regular clay.
>
Now I'm not an engineer but I'd hazard that the holes prevent crack
propogation. Also weight for weight the paper clay will be stronger, and it
may therefore be better able to support itself than the same construction
solid.
Roly
Angela Davis on wed 25 feb 04
HI John,
I really have no certain knowledge but your question made me think
of honeycombs, corrugated cardboard, I beams and arches. I imagine
the fired paperclay has millions of these structures internally where the
paper
has burned away and this could be the reason.
Maybe an engineer out there will tell us the whole story.
Angela Davis
"Have joy in everything you make."
----- Original Message -----
From: "John Miller"
To:
Sent: Wednesday, February 25, 2004 1:30 AM
Subject: Paper clay burnout?
> Hi All, After paper clay is fired and the paper fibers have burned out,
> how can this be stronger than regular clay.
>
> It would seem that the fibers that do make it stronger in dry form, but
> the same with thousands of holes burned through it would weaken the body.
>
> Enlighten me on this.
>
> Thanks, John
>
>
____________________________________________________________________________
__
> Send postings to clayart@lsv.ceramics.org
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Ababi Sharon on wed 25 feb 04
In some cases it will be the same in some cases it will be fragile like
hell!
Depends on the claybody you use and the amount of paper.
Yet I vote PPclay!
Ababi Sharon
Glaze wizard
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://ababi.active.co.il
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
A fast link Ceramics forum in Hebrew:
http://www.botzpottery.co.il/kishurim.html
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of John Miller
Sent: Wednesday, February 25, 2004 8:31 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Paper clay burnout?
Hi All, After paper clay is fired and the paper fibers have burned out,
how can this be stronger than regular clay.
It would seem that the fibers that do make it stronger in dry form, but
the same with thousands of holes burned through it would weaken the
body.
Enlighten me on this.
Thanks, John
________________________________________________________________________
______
Send postings to clayart@lsv.ceramics.org
You may look at the archives for the list or change your subscription
settings from http://www.ceramics.org/clayart/
Moderator of the list is Mel Jacobson who may be reached at
melpots@pclink.com.
Snail Scott on thu 26 feb 04
At 01:30 AM 2/25/04 -0500, you wrote:
>Hi All, After paper clay is fired and the paper fibers have burned out,
>how can this be stronger than regular clay.
>
>It would seem that the fibers that do make it stronger in dry form, but
>the same with thousands of holes burned through it would weaken the body.
Yes, that is exactly right. It is extremely strong
as greenware, but less strong after firing than
a conventional clay would be.
-Snail
Ababi Sharon on fri 27 feb 04
Yes I think Snail, you are right.
The point is: If the clay is thin it might be a problem. However I found
out some claybodies hardly effected while others disaster
Ababi Sharon
Glaze wizard
Kibbutz Shoval Israel
ababisha@shoval.org.il
http://ababi.active.co.il
http://www.matrix2000.co.nz/Matrix%20Demo/Ababi.htm
A fast link Ceramics forum in Hebrew:
http://www.botzpottery.co.il/kishurim.html
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Snail Scott
Sent: Thursday, February 26, 2004 6:45 PM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Re: Paper clay burnout?
.
rosette@SPEAKEASY.NET on fri 27 feb 04
Someone forwarded me an email regards some confusion--so maybe I can clar=
ify the misunderstandings that seem to abound...
First- as suspected-yes a miniature cappilary network of intewining strin=
gy rootlike voids remains after early burnout of the cellulose fibers in =
a clay body--hold on though...thats just the beginning...see electron mic=
rographs in my books...as you know paper burns out nearly the same time w=
as burnoff occurs about 450F--just after the boiling point of water steam=
hopefully escapes out the pores as well....there is in fact less paper b=
urnoff from the interior body of most paperclay than the average person s=
tuffs crumpled newsprint inside sometimes..to put it in perspective.....
Second...by bisque temperatures about cone 04-- you have an open clay bod=
y for most all clays even the earthenwares and terracottas... at bisque t=
his is why paperclay bisque repairs can sometimes be accomplished with fr=
esh paperclay slip--the paperclay slip being like a liquid velcro of fibe=
r free floating--when it hits the porous bisque, a water osmosic sucks te=
ndrils of fiber down in the micro pores-hollow tubes at the surface, the =
tendrils harden up stiff as the water drys out and snag is the name of th=
e game! This happens also at bone dry stage of paperclay when wet p'slip =
is added...hence the adhesion is more mechanical at this stage between bo=
th parts...godd adhesion wet to dry requires enough pulp in the mix...too=
little and no go...
Third...There is a cone 5-6 threshold so for stonewares and porcelains mo=
re interior melting is going on....mullite crystals are forming and so on=
...just as they do in traditional clay... however-- I believe micromelt i=
nside the clay body starts to occur gradually as the interior voids slowl=
y fillup with seeping driplets of micro glass...in most clay bodies..espe=
cially porcelains.... thus high firing requires attentiveness to amount o=
f reduction and even heat and so on to avoid slumping a few degrees earli=
er than would be...This is not the case in low fires... So at a certain t=
empreature just before vitirfication you would have as strong a body as t=
he original recipe or possibly stronger depending on what is in there... =
and there are lots of clay body hardeners, kyanite being one...but lots a=
nd detailed research would be great. of some one were to undertake it....=
.
Fourth--have done water of asorbtion testing for various paperclay bodie=
s all over the world... and its not the paper content--necessarily that a=
ffects porousity as the single factor--have gotten to less than 1/2 of 1%=
water of absorbtion in even some kinds of of lowfire paperclay bodies...=
Glass like vitirification is not necessarily what is wanted or needed for=
art purposes.... since glaze seals pores well . Theres another way to ap=
proach this subject than what I learned in school...that works. Generally=
the shrinkage difference is only about one percent less than traditional=
clay--not significant...per se.... I've got alt more info on this in cha=
pter three of the new book...large scale work has its own set of new rule=
s it turns out.
Fifth...for sculpture I'm finding that the cappilary network of pores in =
paperclays... is more beneficial- for thermal expansion--not just in raku=
for any body..no grog is required at all!...but also for temperature cha=
nges after fire...such as freeze thaw... "breathing" claybody even porcel=
ain is surviving the 40below zero deep freeze Canadian winter testing I'v=
e been giving it!!!!! wow..
Its hard to give a simple answer because clays, papers and climates and u=
sers and kilns...vary so much...but hopefully this helps...
Sincerely, Thanks for your post...
Rosette
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