Jon Pacini on mon 14 apr 08
Michener would be proud
Greetings All--- All clays are not created equal.
It would be nice to think that there are Master Clay Formulators out there,
working at clay suppliers, developing only perfect clays for clay companies
that will work under every conceivable condition. But that is not the case.
What there generally is, is a fellow who makes clays that the formulas, over
the years, have been supplied to him from Teachers and Potters and the
occasional Industrial user. It's the rare clay company that has a Lab or
even a clay tech, that specifically develops clays for the company.
Most clays are developed by somebody who has a specific use in mind.
Teachers tend to develop clays for general use---throwing and hand building
by students. A clay that is forgiving when working and in firing. These tend
to be fireclay based bodies with sand or grog additions.
Potters develop clays that match up to the type of ware they want to
produce. Functional potters gravitate to the smoother, dense bodies of
various colors. These tend to need a bit more skill in throwing as they lack
courser tooth. And depending on a potters preference, they may want the clay
soft or firm.
If you have fallen in love with the color of a given clay, but you are
lacking a bit of the skill to throw it, wedging in Grog or sand can be your
salvation. B-3 is a unique formula---no telling why it was formulated the
way it was, but it's best used in small amounts. I've modified B-3 Brown to
throw larger by adding grog to it and it makes a world of difference. But
then you end up with the lighter grog speckles in it.
Getting the clay to a firm consistency will also help. As a production
trained potter, I like firm clay. It pulls up tall and can be stretched out
thin horizontally. Also if you are the type that uses a lot of water, it's
always a good idea to start off with as little water in the clay as
possible. Over the years as hobby potters and older potters have become more
numerous, there has been a preference developing for softer clays. And
though a softer clay is not as hard on the body joints, it generally doesn't
hold up as well during forming as a firm clay.
Many clays that a manufacturer stocks can feel inconsistent from batch to
batch to batch. Particularly if you are purchasing clay from a distributor
on an occasional basis. For the most part the clay doesn't start off hard.
Fresher clay is almost always softer than older clay. A distributor may
purchase a couple of tons of any given clay and sell it over a period of
many months depending on the demand for that clay. If you buy a clay in
January and it's soft and go back and buy more in April and the clay is
hard, it may be from the same batch. And vise versa. You may get old stock
initially, which is firm, and come back and get soft new clay the next time.
The tendency is to think ---"can't they make this stuff the same way every
time?". Well, I can't speak for all clay companies, but here at Laguna we
make our clay in long runs and have many checks during production to insure
consistency. We do tend to make clay in a manner in which it can sit at a
distributors for a while and not become overly stiff. So if you get very
fresh clay, it can be overly soft and then there is still no guaranteeing
that the distributor will rotate his stock and you will not end up with a
couple of boxes of extra firm clay that have been laying around. Boxes of
clay should have a sequence number on them. Different companies use
different codes but you should be able to call them and find out when the
clay was made. If it's new, it should be soft ---if it's old, it's going to
be firm.
It's always best to check the firmness of a clay when you are purchasing it,
not after you have driven 2 hours home and unloaded it and are ready to sit
down at the wheel. Clays tend to feel firm when sitting in a box. You can't
definitively tell what the firmness of a clay is by pressing your thumb on
the block. Don't get me wrong---it can be tested that way if you like tooth
paste---but clay 'at rest' in a box is almost always firmer than if you cut
off a slice of clay and ball it up. That is why many manufacturers will tell
you to drop the clay or bang it around a bit. Clay can be a bit thixotropic
because of leaching alkalis. By moving it a bit, it will give you a better
idea of the true firmness of the clay.
Also keep in mind that the plastic bags your clay comes in are not air
tight. If you live in a very dry environment, the clay will dry out faster
than if you live in a humid one. When I lived in Hawai'i I purchased my clay
3 tons at a time and I never had a drying out problem. One of the best ways
to keep your clay soft is to have a damp closet. I keep mine in a plastic
barrel with wet towels on top.
Best regards,
Jon Pacini
Clay Manager
Laguna Clay Co
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