iandol on sat 30 mar 02
Nigel Wood (1999) writes interesting comments about the Jun Blue glazes. =
He contrasts the opinions of Tichane who has demonstrated the presence =
of a two liquid system with those of Kingery and Vandiver who propose =
the "breakdown" of P2O5(P4O10) to P2O3 as being the reaction responsible =
for the release of gas which forms the bubbles.
Without access to thermodynamic information giving values for Heats of =
Formation and Entropy it is not possible to say much about the chemical =
reaction proposition or to calculate the equilibrium temperature for the =
reaction P2O5 <-> P2O3 + O2, but the idea of two immiscible fluids has =
been demonstrated by a Russian team who mapped this in the =
Na2O-CaO-Al2O3-SiO2-P2O5 System.
Nigel Wood does confirm my suspicion that thin slivers of Jun glaze =
viewed against the light show the complement of blue. I think if bubbles =
can be seen with the naked eye or even through an optical microscope =
they are much too large to cause the physical effect of "Back =
Scattering" and that they cause opacity because of the large difference =
in refractive indices of a gas and the glass.
I suppose we should ask the Geologists if there are precedents where, in =
a silicate system, you can have immiscible silicate fluids forming, with =
or without the presence of Phosphorus. A search for information about =
the production and properties of Phosphorus Glasses is not very =
rewarding, except that they seem to be water soluble.
Certainly an interesting topic,
Hoping all are having a peaceful Holiday.
Best regards,
Ivor Lewis. Redhill, South Australia
Lee Love on sat 30 mar 02
----- Original Message -----
From: "iandol"
>show the complement of blue. I think if bubbles can be seen with the naked eye
or
>even through an optical microscope they are much too large to cause the
physical
>effect of "Back Scattering"
If you have Hamer's dictionary, you can see a black & white photo of the
bubbles at the end of the Chun listing. I don't know how small the bubbles
get (just because there are big bubbles, doesn't mean there aren't small ones)
but I do know that there are ones visible to the naked eye. When the glaze is
thick, it is opaque white, with only a hint of blue.
--
Lee In Mashiko Ikiru@kami.com
"Far too many of us use our hands like inert flippers." -Philip Rawson
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