David Woof on tue 8 mar 05
now you get to try something new. please post your results.
commercial castable refractories usuall contain a high temp aluminous cement
and for very high temp up to (1800 c) a calcium aluminate with corundum as
aggregate is a likely composition.
In my experience the refractory industry and it's supply sources are
secretive about the composition and access to these raw materials. may I
suggest contacting AP Green, I'm sure they will assure you it contains no
portland if such is the truth when you explain your concern.
Lowell Baker published his research in castables some time ago. find him
through this group, or Ceramics monthly......American Ceramic Society.
It doesn't seem like you made a very large batch. I wouldn't put time in
to throwing fine utilitarian pottery but what about some more rugged
expressive sculpture, platters or wall pieces where pop outs make an ongoing
changing exhibit complementary to your other surface treatments.
every so-called screw-up is really so only when boxed in by preconcieved
expectation. use it as a doorway to new paths and adventure. Perhaps one
of your students is the next great master or clay messiah just waiting to
break out of the box. be there for her or him.
It's not new for us to put all sorts of stuff including portland in our clay
to see what will happen next.
Have fun, always
David Woof
peering over the edge, reverently taking an irreverent look at everything.
jsfreeman@DMCI.NET on sun 13 mar 05
Well, the problem solved itself. We made a pinch pot out of the stuff and
bisqued it with no problem. We were going to high fire it, but when we
opened the barrel containing the contaminated clay two days later, we found
that it had indeed set up into hard, unworkable chunks even from the tiny
amount of castable that was added. We broke it up and trashed it.
The supplier faxed over the chemical breakdown of the castable. It appears
to have about 5% portland cement in it, more than likely to give it
air-setting properties.
We thank everyone for their assistance.
...James
wjskw@BELLSOUTH.NET on mon 14 mar 05
Here's another interesting experiment, then.
Would adding a smaller percentage of Portland cement to a clay body
improve green strength, without "contaminating" the body, or
compromising another quality of the body?
Sounds like the answer for those folks complaining about porcelain
being like throwing "cottage cheese". Perhaps those thin droopy
rims on plates and platters could benefit? Hmmm...air setting
properties....
Just my 0.02...
Wayne Seidl
Well, the problem solved itself. We made a pinch pot out of the
stuff and
bisqued it with no problem. We were going to high fire it, but when
we
opened the barrel containing the contaminated clay two days later,
we found
that it had indeed set up into hard, unworkable chunks even from the
tiny
amount of castable that was added. We broke it up and trashed it.
The supplier faxed over the chemical breakdown of the castable. It
appears
to have about 5% portland cement in it, more than likely to give it
air-setting properties.
We thank everyone for their assistance.
...James
URL Krueger on wed 16 mar 05
On Monday 14 March 2005 07:57 am, wjskw@BELLSOUTH.NET wrote:
> Would adding a smaller percentage of Portland cement to a
> clay body improve green strength, without "contaminating"
> the body, or compromising another quality of the body?
Wayne,
Once moisture gets to the cement the hydration reaction that
causes it to "set" or harden would begin. Therefore, it
would have a limited pot life as opposed to a limited life
as a pot.
Earl K...
Bothell WA, USA
| |
|
