Materials
CLAY
I have experimented over the years with many different types
of clay, including ready-made plastic commercially-available
clays, and have come to the conclusion that the only way to
guarantee a first-class clay body is to makes one's own. This,
of course, means substantial equipment but the benefits far outweigh
the loss of workshop space.
The benefits are:-
- powdered (dry) clay is cheaper by weight
- you can formulate a body chemically appropriate for your glazes
- you can formulate a body geared to your making processes
- you can eliminate waste by incorporating slops easily
The two main pieces of equipment needed for this are:-
- a heavy duty mixer, typically a bakers' dough mixer and
- a pug mill, preferably de-airing
When I am mixing a new batch of clay I find that 5 gallons of
slops to 100lbs of dry materials usually combine to produce
a body of the right consistency. I used to worry a lot about
the fired colour of the body, preferring warm dark buff colours,
but these days I am more concerned to have a light-firing colour
as this helps translucent glazes. I have also moved away from
using body additions such as nepheline syenite, fireclay and red
clay to a point where the body formula is about as simple as it
could be:-
56lbs HYPLAS 71 ball clay
28lbs HYMOD AT ball clay
13lbs 40s to dust silca sand
4galls wet slops
+ water if necessary to taste
These are all mixed in my dough-mixer and then pugged. The above
quantities make about 180lbs of plastic clay.
GLAZE MATERIALS
From day one I have always made my own glazes partly because the
whole area of glazes is an endless adventure and partly because
it is hugely cheaper in the quantities I get through. And of course
I am continually experimenting and modifying. The materials I keep
in quantity are:-
- barium carbonate
- basalt dust (free from a local quarry)
- borax fritt standard
- china clay (I'm not fussy)
- cobalt carbonate and oxide
- copper carbonate and oxide
- cornish stone
- crocus martis
- dolomite
- flint
- ilmenite
- limestone dust (from a local producer (£1.00 per 25kg.....)
- lithium carbonate
- manganese dioxide
- mixed wood ash
- nepheline syenite
- potash felspar (preferably FFF)
- red iron oxide (the synthetic variety)
- rutile
- talc
- tin oxide
- titanium dioxide
- wollastonite
- yellow clay (local)
- zinc oxide
- zircon silicate
Some of my glaze recipes can be found on my glaze
pages using various combinations of the above materials. It is well
worth while scouting round your local area for quarries where dust may
be available either free or ridiculously cheap. For years, before the
quarry closed, I used a dark sandstone dust from Triscombe quarry in the
Quantock hills which, crudely,
was an acceptable substitute for felspar. I think it was either Harry
Davis or Michael Cardew who said that it is possible to source all the
materials you need for pot-making within a 25-mile radius of your workshop.
The area in which I live would certainly yield everything if I extend the
radius to 50 miles.....
Updated 5th February 2009