Pfeiffer, Dan R (Dan) on mon 24 jan 05
We did a test tile with a copper wire sitting in a small dent in a slab of
clay. fired to ^10. What would you expect to happen?
On a different tile we had wire and clear glaze, the result was the same but
I do not understand why things worked as they did. The copper when through
the tile and the cookie under the tile and into the shelf. It would seem a
high copper content is not a good idea for more reasons than food safety!
Any ideas as to what happened? Did the copper flux the clay and shelf or
just "leak" through the clay. The shelf has holes like the copper melted it
and not just sank into it. No holes in the clay tile that we could see but
it would be much harder to tell as it left a black smooth surface with the
tile wielded to what was under it.
Can the shelf still be used? I was thinking maybe I could put kiln wash over
the hole after removing a bit of the shelf top.
Dan & Laurel in Elkmont AL
Snail Scott on tue 25 jan 05
At 01:03 PM 1/24/2005 -0600, you wrote:
>...The copper when through
>the tile and the cookie under the tile and into the shelf....
>Can the shelf still be used? I was thinking maybe I could put kiln wash=
>the hole after removing a bit of the shelf top...
The melting point of metallic copper is=20
around 1800 =BAF - still basically solid at=20
low bisque temperatures, but very, very=20
runny at stoneware temps - enough to=20
dissolve the clay surrounding it. If you=20
want to keep using the shelf, make sure you=20
grind out ALL of the copper, not just the=20
top, or it will continue to eat away at=20
the shelf. (Try one of those carbide stone=20
bits in your drill.) If the resulting divot=20
is not too huge, just fill it with kiln=20
putty and use the shelf normally. If it=20
is a BIG pothole ;) reserve that shelf for=20
Lou Roess on tue 25 jan 05
on 1/25/05 6:33 AM, Snail Scott at snail@MINDSPRING.COM wrote:
If the resulting divot
> is not too huge, just fill it with kiln
> putty and use the shelf normally.
Snail, What is kiln putty? something you buy or something you mix up
Lou in Colorado
Ivor and Olive Lewis on wed 26 jan 05
Dear Snail Scott,
You say <still basically solid at low bisque temperatures, but very, very runny
at stoneware temps - enough to dissolve the clay surrounding it. >>
Accepting a ball park figure for the melting point of metallic copper,
say 1950=BA F, what sort of refractories are used during the smelting of
the metal if the molten metal can dissolve ceramic materials ?
Do we really know what chemistry is taking place in the example given
? Isn't copper one of those metals that rapidly oxidises when heated
to red heat?
I would have liked to have had my hands on the specimens.
Snail Scott on wed 26 jan 05
At 09:31 AM 1/25/2005 -0700, you wrote:
>Snail, What is kiln putty?
Kiln putty is the same as kiln wash, only
thicker. If you have a big jar of kiln wash,
that thickened glop that accumulates on the
sides is it! (Or you can make a separate
batch with less water.) That's all.