John Harlow, Pennard Pottery Materials Used Currently

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.....
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This page last updated 3rd September 2006