douglas fur on tue 5 may 09
Stephani
Here's a couple of provocaturish ideas...
- A potter I knew back when... used whiting as his flux [about 5%]. He
was self taught and loved doing the wrong things. (As was once said of m=
y
work "willfully perverse")
- I've done a few tests (^5-6) with bone-ash that look promising
DRB
Seattle
On Thu, Apr 23, 2009 at 1:41 AM, Stephani Stephenson m
> wrote:
> I have been making clay again.
> so the conversations on clay substitution, prospected clay, new fireclay,
> all have my
> ear/eye.
> Before i mixed I pondered. I thought about what i wanted from this body t=
o
> be.
> I want a warm buff which will work for tile and architectural purposes.
> I may want 2 versions of it..one nice toothy version for handbuilding, a=
nd
> one with a
> finer composition. 3 versions actually, the third, sans grog, to use as a=
n
> slip.
> I work mainly with red clay, but I also work with buff clays. I currenty
> use 2
> commercial buffs. one which is too coarse , immature, and crumbly at thos=
e
> temps, and
> the other which has too high a shrinkage for my liking. There was a third
> which makes
> bullet proof strong tile at cone 5-6, but sets up hard in the bag, AND
> strangles the life out
> of every glaze i ever tried on it.
> none gives me quite the color i want.
> I reviewed all the samples i had tested previously and reviewed what it w=
as
> I liked about
> each one and whether it would serve the purpose .
> I checked books, to remind myself what they had to say about clay bodie=
s
> in the
> high earthenware to mid fire range... cone 01 to cone 3, for example,
> and found, a very general range of information, to say the least!
>
> So I ponder what Rhodes, Hopper, Peterson, King, Cushing, Speight, and
> Zakin,etc. all
> have to say.
> I compare notes.
> I review a number of bodies I tested a few years back. I tested a body
> John Britt sent to
> me, Thank you John, it was a nice claybody. I tested four versions of it,
> subbing
> fireclay/stoneware clay and ball clays , to see how the substitutions
> affected the look as
> well as the stats. I tested a Randal, a Cushing, a Vance, a Neymark, a
> Blossom, and a
> few more, including a few commercial bodies. At that time the ones I mix=
ed
> , I mixed by
> hand.
>
> What was very beneficial to me was testing clays individually. I fired
> samples of ball
> clays, fire clays and kaolins, comparing shrinkage and color:
> Old hickory #5, OM4, dresden, XX saggar, tile #6, lincoln, imco 400,
> goldart, hawthorne,
> roseville, and so on.
> i compared thei composition, but more importantly, I became more famili=
ar
> with what
> each felt like and looked like .
> I started doing this years ago, because of Susan Peterson. In her book ,
> she had those
> wonderful charts, showing fusion tests of all the different materials at
> different
> temperatures. I got that book when it was first published and pored over
> those images
> with a loupe... it had never occurred to me to melt materials
> individually , to form an
> image in my mind of what happened to them in the melt.
>
> In my quest for a clay body, I want to understand the chemical, element=
al
> composition.
> but what drives me is sensory, the search for something which looks,
> feels and
> responds to handling and firing in a certain way. I see it in my minds
> eye. my fingers
> will know it when they dig into it. I don't have a claybank outside so i
> have to find it with
> mixing powders.
> Clay du Jour...a lovely mix of spices and crunchies!
> Lincoln and Imco 400, from the same clay but oh, so different to the
> touch. another clay
> i am intrigued with is the new Neuman red, i think it is the gladding
> mcbean clay inpart.
> a light red , very coarse clay. a toothy mealy clay. yum, yum. how much
> of this can i
> use for color and in lieu of grog? maybe save it for another claybody.
> pyrophillite, like calcined clay, to bring down shrinkage.
> Old hickory #5 ball clay because it doesn't darken the clay like om4 a=
nd
> will show
> colorants in the unfired state, if I use them.
> and the question of fluxing to bring down the firing range?
> i am wary of frits because they tend to narrow the firing range, even
> 3134, which is a
> wide firing frit, plus they can make the clay harden up in the bag.one cl=
ay
> body called for
> frit 3269 , a flux which has zinc, and maybe only later would you realize
> how that
> affected glaze color . How much talc can i use before it causes the clay
> to feel rubbery
> and not join well? wollastonite ..had trouble getting that to mix last
> time, and what about
> neph sy,hmm, sodium again, though maybe better for lowering maturation, o=
r
> best to
> stick with a custer or g200 felspar?
> Frit, alumina hydrate,skip those, adds to expense. kyanite may knit it
> together, but it
> adds alumina.
> and then there is grog. finding the right mix of coarse, medium and
> fine... i have the
> ratio for strength, how much can I tweak it?
> chemical analysis helps alert me to these things. It tells me , how much
> silica, how much
> alumina, how much calcium , iron , titanium..
>
> but it cannot tell me, how will this feel in my hands?, how will it join?=
,
> how thick can i
> work? how will it react to my glazes? will it flux them, dry them, ...wh=
at
> color will the
> clay be in oxidation or reduction?
> will it be strong or brittle , especially with additions of grog?
>
> So you give it your best guesses and it's kind of fun, actually.
> And your best guesses get more informed, over the years (tortoise noises)
>
> with the mixer and the pugmill , i am looking forward to making some
> 'boutique' (ooh la
> la)
> size batches to test....
> thinking i could possibly make the clay body i dream of!
> or at least learn in the process. I'll share it as it goes.
>
> Stephani
>
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