Paulette Carr on thu 17 feb 05
Eric,
In mid January I made up a test batch of a glaze that is 70% neph sy.
I opened it last night to apply to the test tile, and found it still
fully suspended, and the brushing application easy. I used VeeGum Cer
(VgC) - 1.5% for this particular glaze- in the preparation of this
glaze. Since I have been using the VgC, I have yet to find a glaze
that has separated, and solidified on me. I know that you said that
VeeGum seems to alter the crystal pattern, but, other than an
application thickness problem, I cannot think why. (Maybe Ivor, or
another theorist can offer an explanation.) By the way, addition of
other clays will alter the glaze, increasing the amounts of Al2O3,
SiO2, etc.
If it were my glaze test, I would prepare a small amount (300 g) with
VgC or epsom salts, and test myself. The appearance of the fired glaze
has as much or more to do with the method of application and firing as
with the suspending agent. Perhaps, the application of this glaze with
a suspending agent is not as thick as one would think it is, because it
looks so thick in the jar/bucket. Scratch when dry, and if not as
thick as the application without the suspending agent, you should
reapply until it is. Then, document the firing parameters to make
certain that it is the same as the firings where you saw the results
you liked. Now you will be comparing apples to apples.
I will still put my money on the VgC as a suspending agent - at least
98% of the time -and because it also contains CMC, the surface is firm
(rather than powdery) when dry!
Good luck!
Paulette Carr
Paulette Carr Studio
Member/Potters Council
St. Louis, MO
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