Janet H Walker on mon 24 feb 97
I sure hope this isn't just duplicating what others have had to say
in posts I haven't read yet. If so, just skip on by...
Tiggerbus says:
...I am new to this mixing thing. I need information on what
to purchase to mix glazes for an electric kiln...
It takes a surprisingly long time to figure out the answer to this
question when you are going from a standing start! I think I finally
now have everything I will need but it has taken almost two years to
learn enough to know what to buy. And how much to buy. (God knows
what I am going to do with the 10 pounds of bentonite...)
First, you need two or three really good recent books on glaze
formulation so you don't wade around looking at recipes that all
look to same to you or all contain chemicals that you don't want in
your house. There have been plenty of suggestions on ClayArt
recently so look in the archives (lots of folks were giving advice
around Christmas time!!).
Some good ones are Mimi Obstler "Out of the Earth; Into the Fire"
and Robin Hopper's Ceramic Spectrum. Also Currie's Stoneware
Glazes. If you just want some recipes instead, checkout the various
major compendia by E. Cooper, J. Conrad, and J. Chappell. Most
libraries have at least one of these. (If you're buying, call up
the Potters Shop, Needham, MA).
As you read through the recipes you'll get the picture about which
ingredients show up a lot and which ones you might need a lot of.
In order to get started testing though, you have to BUY something.
I am going to attempt to list the things that you will probably end
up with after two years, regardless what you think now!!
Oddly enough, you should probably buy a whole lot of the major basic
ingredients. This is because some of them are quite variable in
composition over time (since they just dig 'em out of the ground and
you get what you get) so if you've gone to a lot of trouble learning
and testing, you want to at least cash in on your work by having the
same ingredients to work with awhile. (Other people may advise you
differently but this is what I've decided!)
This first group, you'll probably want 50 lb each. Since this is a
full bag, it is almost cheaper to get a lot than to get 10 lb.
Except for the shipping, which you'll have to factor in. (I hope
someone can tell me what I should have bought for storing the bulk
ingredients!)
Fluxes:
Potash feldspar (Custer is a standard)
Soda feldspar (Kona F-4 is a standard)
Gerstley borate, although some people recommend a boron frit instead
Whiting (aka limestone or calcium carbonate)
Dolomite (aka dolomitic limestone)
Spodumene (like a feldspar, with lithium carbonate)
The following also provide the fluxes and are somewhat more
expensive but often work better than the things in the first group
that they are used instead of:
Soda frit, like Ferro 3110 or equivalent (instead of spar & whiting)
Boron frit, like Ferro 3124 or 3134 (instead of Gerstley borate)
Talc (instead of dolomite, for magnesium)
Nepheline syenite (a feldspar with nice properties)
Wollastonite (instead of whiting, for calcium)
Specialty fluxes in "pure" form for special purposes (lesser
amounts, like 5 lb)
Magnesium carbonate ("lite", a fluffy powder)
Lithium carbonate
Strontium carbonate
Zinc oxide
Clays (common and highly variable ingredient, get lots)
Kaolin, EPK is a standard
Ball clay, often Tennessee
Bentonite, tiny amounts for conditioning glazes
Red clay, often Cedar Hts Red Art clay
Slip clay, often Alberta slip or an "Albany slip substitute"
Opacifiers (small amounts usually, so maybe 5 lb)
(Listed from most to least common)
Tin oxide ($$$)
Superpax
Bone ash (synthetic not natural)
Titanium dioxide
The glass former, always listed last but not least:
Silica, 300 mesh
Colorants (very small amounts of most, except iron; start with 1-2 lb)
Red iron oxide (Spanish)
Rutile, light ceramic grade (you rarely need milled)
Copper carbonate
Cobalt carbonate
I draw the health & safety line right about there although I will
keep and sometimes use a very little (~ 100g)
Manganese dioxide
Chrome oxide
I do not have any compounds of barium or lead, not even frits. It
just isn't worth it taking the chance.
The only other things I can think of:
Cornwall stone (variable and exasperating material, not essential)
Ash (wood, charcoal etc; variable and exasperating, lots of fun)
Ash (volcanic; ditto)
Eventually you may get "into" stains; others can advise!
I guess that's it. Maybe I've said enough that you're ready to
start looking into commercial mixed glazes! Gosh, I can't believe
I'm going out on a limb like this publicly. I'm sure I've made some
hilarious gaffe here; be gentle guys.
Best wishes to Tiggerbus in following The Glaze Trail.
Jan Walker
Cambridge MA USA
Dave and Pat Eitel on wed 26 feb 97
>----------------------------Original message----------------------------
>
Jan Walker's approach to figuring out what chemicals to buy is excellent
and very thorough, but it requires one to purchase a LOT of stuff. My
advice would be to take a number of glaze recipes--say 20-- in the
temperature range, colors, surfaces, etc that you might want to test. Make
a list of the ingredients and notice the proportions--as Jan indicated
you'll need a lot more clays and feldspars than you will oxides and
opacifiers. For testing purposes, I'd buy smaller quantities at first.
Maybe 10-25 pounds of the things you'll need more of and a pound at most of
the others. You can make a lot of 100 gram tests with 10 pounds each of
such ingredients as custer feldspar, EPK, OM#4, whiting, dolomite and
siilica and a pound of cobalt carb, rutile or iron oxide. Over time, as
you continue testing, I'd just buy the new ingredients that show up in the
new recipes in small quantities. Over the years I've elected to store
minimal amounts of ingredients and order them as I need them. Bags and
bags of stuff take up a lot of space. I've got a bunch of plastic lidded
containers that hold about a quart, and I use these to store all my
ingredients for testing.
Later...Dave
Dave Eitel
Cedar Creek Pottery
Cedarburg, WI
pots@cedarcreekpottery.com
http://www.cedarcreekpottery.com
Patsy Catsos on fri 28 feb 97
Two inexpensive, helpful books that I used to get started glaze making are:
Glaze Projects by Richard Behrens, Professional Publications, Inc.
Ceramic Glazemaking by Richard Behrens, Professional Publications, Inc.
Both of these are available through Ceramics Monthly. Forgive me if this is
a redundant suggestion--I've missed some of the posts to this thread.
Patsy Catsos
USA
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