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glazes containing vanadium pentoxide

updated sat 15 feb 03

 

David Hewitt on wed 12 feb 03


I am currently testing a number of glazes with up to 10% Vanadium
Pentoxide added.

If I leave a mix for, say, two weeks, and open the container without
disturbing the mix, I find that orange 'crystals' have developed on the
top of the mix. The glaze is well suspended as if the Vanadium has acted
as a flocculant. A similar pot with the base glaze only has settled
quite a bit so I can see the difference quite clearly. If I try to
reconstitute the glaze with the Vanadium Pentoxide the 'crystals' do not
break up or go through a 100 mesh.

If I dip a test tile with the glaze containing the 'crystals' it dries
with a rough appearance, has some pin holes and tends to crack. If I dip
a test tile after sieving (anything over 100 mesh removed) it forms a
nice smooth deposit on the test tile. I have not yet fired these to see
the difference, but presumably there will be.

Has any other user of Vanadium Pentoxide had similar experience and, if
so, can you please explain the mechanism that is going on? Also am I
correct in thinking that this makes any glaze with Vanadium Pentoxide
difficult to keep? That is, it should be used within a day or so of
mixing if predictable results are to be expected?

Trusting that there is someone out there who can help answer these
questions and add any other oddities about using Vanadium Pentoxide to
those above.

David
--
David Hewitt
David Hewitt Pottery
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ.
Tel:- +44 (0) 1633 420647
Fax:- +44 (0) 870 1617274
Web:- http://www.dhpot.demon.co.uk

iandol on thu 13 feb 03


Dear David Hewitt,

Sorry to have to be the one to tell you this but it would seem as though =
your Vanadium Pentoxide is water soluble, and substantially so. Not so =
Vanadium(2)oxide and Vanadium(3)oxide.

Best regards,

Ivor Lewis.=20