Cheryl L Litman on tue 13 jan 98
Ron,
Here's a simple cone 6 oxidation glaze we use at Raritan Valley Community
College. Pat Mase developed it and her philosophy is no more than 5
ingredients and whole numbers.
I've never used the base alone but there are 2 very nice oxide
combinations she found. The glaze does tend to settle into a hard lump
in the bottom of the bucket.
Mase's Base: cone 6-7, oxidation, semi opaque, nice matt surface
50 NS
20 whiting
5 talc
5 EPK
20 silica (325)
Red/green:
5 copper carb
Matt Black:
3 cobalt carb
3 black iron oxide
Cheryl Litman
Somerset, NJ
email: cheryllitman@juno.com
On Mon, 12 Jan 1998 13:44:09 EST Ron Roy writes:
>----------------------------Original
>message----------------------------
>I was going to leave this alone but - while I do think cost of
>materials is
>important - I think having stable glazes is the better strategy in the
>long
>run.
>
>Cutting down on the number of materials in a glaze will make weighing
>them
>out less tedious but - you leave yourself open to losses due to
>variations
>in many of the chemicals we rely on.
>
>Even our feldspars go out of production - dividing the feldspathic
>content
>of a glaze makes replacement much easier. I recommend having at least
>5
>materials in any glaze. If some of those materials are more variable
>than
>others I recommend replacing some of that material with more stable
>ones.
>Gerstley borate is a good case in point. If you have 20% in a glaze
>you are
>asking for trouble - especially if that glaze is not balanced - in
>other
>words relying on an over or under supply of some oxides for a special
>effect. I recommend replacing some of that GB with a boron frit - more
>expensive - but in the long run - less expensive.
>
>Keep in mind the problems suppliers have - we tend to buy at the
>lowest
>cost. This forces suppliers to sometimes change their supplier - to
>stay
>competitive - If you are buying a bag of whiting every 2 years - what
>happens if you are relying only on whiting in your glazes - instead of
>sourcing CaO from dolomite, talc and wolastonite - and your supplier
>decides they are going to save everyone some money and buy their talc
>from
>a different supplier? The new whiting may not have the same analysis
>as the
>old one. It is the same with other materials as well -
>
>If you do think it's a good idea to have simple glazes - you had
>better
>test your glazes before you use them on your ware. In the meantime it
>would
>be a good idea to have a complex version - for when things go wrong.
>
>It is quite a simple matter to substitute materials if you are using a
>glaze calculator - and you have realistic analysis to work with.
>
>I'll go a step further - If someone has a simple recipe they would
>like
>complicated - I'll be happy to do the calculations if they will do the
>testing and publish the results. It is not impossible to come out the
>other
>side of an experiment like this and have a better glaze.
>
>>----------------------------Original
>message----------------------------
>>One more point on this - if you need (for instance) magnesium and
>whiting,
>>why NOT use dolomite? Weighing out ingredients is tedious enough,
>why go
>>for 6 if you can get it for 3? I am pursuing, in idle moments, a
>kind of
>>holy grail of really simple and safe (but gorgeous, of course!) ^6
>ox.
>>glazes, with no more than 3 or 4 ingredients. I would love to get to
>the
>>"pants pockets" measuring stage that mel talked about, but my gut
>feeling is
>>that ^10 reduction pulls more out of the materials to make a simple
>glaze
>>interesting at that temp. So far, my best ^6 ox. glazes usually have
>at
>>least 6 and usually 8 or more materials in them. So - back to the
>question
>>- if I can get two or three ingredients from one, of course I'll go
>for that
>>one. Minor variations between batches have never been more than very
>minor
>>in my experience - where I put it in the kiln usually has more
>effect.
>>The only caveat, of course, is when there is a real sea-change in the
>>quality of a material, like happened with colemanite.
>
>Ron Roy
>93 Pegasus Trail
>Scarborough,Canada
>M1G 3N8
>Evenings, call 416 439 2621
>Fax, 416 438 7849
>Studio: 416-752-7862.
>Email ronroy@astral.magic.ca
>Home page http://digitalfire.com/education/people/ronroy.htm
>
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