From: William Melstrom
[william@handspiral.com]
Sent: Wednesday, January 24, 2007 11:50
PM
To: pdh@zircarceramics.com
Dear Phil:
1) Regarding the results from firing #1, is
it typical that the higher the glaze loading the less the tendency to form
crystals?
Point one: The same glaze thickness will
yield different numbers of nuclei on vertical and horizontal surfaces. In
your picture from firing #1, I see no vertical test tiles.
Point two: Yes, usually, the thinner the
glaze, the more nuclei, (but there can sometimes be contradictory
results). However, crystals grow much faster in thicker glaze
surfaces. So, usually, with thicker glaze, you will get less, but bigger
crystals.
2) Regarding the nickel containing piece from the fourth firing is
4% nickel carbonate too high a loading? Do I need to fire at a higher
temperature?
See what happens with 1% nickel and 4% iron. That's the best way
it works for me.
My nickel-containing glazes fire at pretty much the same schedule and
temperature as most of my glazes.
3) What do you think about the streaks,
which I think are as a result on not using a sieve? Nice? Poor
craftsmanship?
My pieces are streaked on purpose, and they (usually) look like it.
Your streaking looks like flaws. Sieve your glazes, and then
add/manipulate streaking during glazing of the piece if that is what you
want.
4) I was thinking of continuing to investigate the colors obtained
by using differing amounts of oxides. Also I thought I'd mix together the
leftovers from my 100 gram test batches to see what I get. Can anyone recommend
mixtures of these colorant to get dramatic effects?
Everyone gets different results, you need to do your own testing.
Maybe you can get ideas from Jon Price's book -- lots of pictures, each labeled
with the oxide percentages.
5) What do you think so far? See any obvious
things screaming for attention?
Slow down on new experiments. Focus on, and perfect your favorite
results. Different oxides need different schedules, so figure out ideal
schedules one glaze at a time.
Begin manipulating the size and number of crystals per your taste.
Higher peak temperature means less nuclei. Longer hold times mean larger
crystals.
Good work, -- William