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vapor damage on elements (was: crystalline glazes -lower temp)

updated fri 2 mar 01


Fabienne Micheline Cassman on thu 1 mar 01

At 12:59 AM 03/01/2001 -0500, you wrote:
> I quarrel a bit with your statement that ZnO starts volatilizing
>at 950 deg C (C08). You may be confusing Zn metal with Zinc Oxide. And
>since you are firing in oxidative conditions there is no way that ZnO will
>convert to Zn metal even at C6 (1230 C). ZnO starts to melt at 1975 C and
>it would not have an appreciable vapour pressure (ie, give off vapours)
>until it was molten. Hence, ZnO vapour will not migrate throughout the
>kiln during the firing of pots covered in runny, high-ZnO crystalline

Thank you for the reply, Tom :)

I don't have a handle on this topic at all and was hoping for a reply like
yours to set me straight. It's a lot for my brain to take in for one
element (Zn) so let me see if I actually understand what you're writing.

Essentially, ZnO will not convert to Zn metal because the temperature is
too low; although the glaze is melted the Zn is still "locked" in there.
So, there are no vapors, thus no damage to the elements, at least from the Zn.

The next question would be, what is in those vapors that could damage the
elements at c/6?

Thank you,

Milky Way Ceramics

Yes, I have learned from my mistakes...
I can reproduce them exactly.