Tom Wirt on tue 8 dec 98
>Subject: Re: Ron Roy's clay company connections
>----------------------------Original message----------------------------
>Well, I can't believe that RR, one of our most dedicated and helpful
>respondants, asked for advice from this opinionated
David
I've got to agree. It is entirely appropriate for Ron to mention names. One
of the biggest causes for problems on this list is the clay we are using!
Although most of the time we are taking the blame on ourselves and our
techniques. Over and over, throwing problems, drying problems, glazing
problems, cracking, etc., etc., are discussed here and only occasionally is the
clay blamed.
I'm not suggesting that, "man if I only had great clay, I could throw anything",
but that, since the mixing and formulas are generally out of our control, we
don't look at clay as a problem source. We simply don't demand enough of our
suppliers. I can't remember the last time I saw a penetrometer hole or even a
thumb print in a pug of clay and I use 1300 pugs of clay a year!
Ron has posted the testing procedures here recently. If the suppliers won't do
it, we should. As I've gone through a series of problems over the last couple
of years (since my supplier changed the guys who are doing the mixing) I've
found
1. They aren't dry mixing long enough, leading to variation in consistency,
especially the amount of grog.
2. Not adjusting the water for the clay moisture content and/or the amount of
clay in the bag. This leads to too wet or too dry a batches.
3. Not mixing wet long enough. I've even found one end of a pug too wet, one
end just right....and variation within a batch can be quite wide.
4. Not either cleaning the mill or pulling the change over clay (between body
types) and selling it as just that. This leads to mixture inconsistency and/or
lumps of mixed but harder clay within the clay. As you throw, the lumps can't
be compressed like the rest of the body.
5. Using inferior greed materials....they're still using Maryland grade grog ev
en though we know it to be frequently contaminated.
6. Developing formulas in the first place that are convenient to mix, rather
than proper for their use.
And the slit goes on. So encouraging the clay suppliers to sharpen up their
skills a bit through our own knowledge seems to be in order.
and knowing who is doing a good job, should help us all.
Tom
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