Charles G Hughes on wed 5 apr 00
------------------
Ok, so I have been looking around at all the advice from various wise souls
about what do about the lack of Gerstley borate, Jeff Zamek suggests G-200
feldspar and frits, Tom Buck has a couple wild concoctions of complicated =
mixes
to make a GB substitute on www.digitalfire.com, but what I really want to =
know,
is, can I achieve the same melt without it? Not knowing for sure about the
complexities of Raku firing, but I assume that I am firing somewhere between=
012
and 05. Is there any reason I can't start with a non -Gerstley Borate based
glaze 012-05 glaze and fire it Raku style then make adjustments from there?
I solved the GB problem in our studio by being brave and yanking the old=
GB
based standards out and bringing in some new glazes, however Raku is a new =
beast
to me and it seems that no one has done much research on Raku firing without
either Lead, Gerstley Borate, or Colemanite. Any advice about making the =
switch
away from GB and not necessarily substituting for it? I just want some nice
glazes that do interesting things.I don't need to keep the old ones and =
their
particular characteristics.
-Charles Hughes
http://www.thecreativeoasis.com
Bruce Girrell on thu 6 apr 00
Charles Hughes wrote:
>Is there any reason I can't start with a non -Gerstley Borate based
>glaze 012-05 glaze and fire it Raku style then make adjustments from there?
It's a perfectly good approach. I suggest that you go about it in a
systematic way, though. Otherwise, you'll likely have a long period of
frustrating glaze experiments ahead of you. Check out
http://ian.currie.list.to/recipe_method.htm
Currie's method will work even if you don't know the components of your base
glaze (as with a commercial glaze). Just use 100% base glaze for corner C.
Choose a base glaze that melts at a pretty low temp so that your useful
results will have more range across the tile.
If you happen to know the constituents of your base glaze, then you may want
to investigate glaze calc programs. Several good ones exist for both PC and
Mac.
Both the recipe approach and glaze calc programs have advantages and
disadvantages. If you are uncomfortable with numbers or you are interested
in finding unique new glazes that may not fall into the class of a "good"
glaze or if you just like choosing between a set of actual samples, then the
recipe method will work well for you. If your main interest is
predictability and good glass formation; if you don't have a problem with
numbers and computers, then glaze calc is for you.
Good luck. Let us know if you find something interesting.
Bruce and Lynne Girrell
in springtime northern Michigan
cooking up a few experiments of our own for the next firing
1) Trying a slip under the glaze to see how it affects the crackle network
size
2) Adding opacifier to the slip to see how it helps the colors
3) Playing with the OxyProbe
4) Trying a porcelain based clay body for raku (lots of molochite)
Tom Buck on thu 6 apr 00
Charles Hughes, it seems, doesn't like my "wild conconction" as a
substitute for Gerstley Borate in Raku glazes. The basic problem is that
the 80GB:20NSy is a widely used Raku base; it is cheap; it works well. If
you wish to develop Raku glazes without GB, then using a Frit is the only
way to get insoluble glaze slurries (Borax is soluble and will not sit
well in a glaze on the shelf). The frits to employ with a redesigned
recipe are 3124, 3134, 3278, 3195 (or their equals). But these frits will
not emulate 80GB:20NSy because the SiO2 (and sometimes Al2O3) will be too
high for a typical Raku firing.
Mr Hughes can try glzcalc and see if his tests yield what he
wants, a departure from 80:20. I fear he will be hard-pressed to get
sastifying lustres.
Tom Buck ) tel: 905-389-2339
(westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street,
Hamilton ON L8T 3E1 Canada
Paul Gerhold on thu 6 apr 00
Pemco Frit 25 will make a good starting point for low firing Raku glazes. You
can order from Highwater Clays in Ashville N.C. Their e-mail is
www.highwaterclays.com.Sorry for such a short message but not much of a
typing person. Good potting.Paul Gerhold in dry Florida.
| |
|
