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A Unique Glaze

By Chas Wethered

Having been a studio potter for a few years prior to my moving to Mendip I had formulated the idea of using digging spoil to make a ceramic glaze.  I had read of potters using found raw materials in the blending of glazes.  A potter of my acquaintance had used alluvial mud from the River Darent in Kent to make a rather good stoneware glaze.

A first and major setback to my plan was that it took nearly two years to get my workshop built and up and running, it also took a lot of hard to find beer tokens, but once work was completed and the power connected I was ready to experiment.  I had been working with the regulars at Five BuddIes Sink on as many Wednesday evenings as I could manage from almost the onset of digging, so like the rest, knew the dig spoil intimately.  Even surface work dramatically increases the thickness and weight of an oversuit!  It also colours any clothing and skin to a rich red that resembles the Masai warriors of East Africa!  This boded well, there had to be a high iron oxide content and of course due to the site a reasonable amount of lead too.  There were other trace metals mentioned in post digging sessions in The Hunters.

One Wednesday about a year into work on the dig I took a 19 litre bucket and emptied a good bag-full of mud and chunks of rock into it, this was then wrapped in a clean bin liner as Robin was being "overly precious" about the interior of his car. The sample was taken from about 25 to 30 feet down from the second shaft on the Stockhill Wood side of the road. My first task was to top up the spoil with tap water, adding therefore chlorine and fluoride but this happens when all glazes are made up.  I let the mixture settle for a few days and then sieved some of the mud through an 80-mesh lawn (not grass, a sieve) adding more water to thin down; the sediment allowing the maximum amount of slurry through the sieve.  Having discarded rocks and other detritus I now had a second bucket with about 12 litres of red liquid.  I let this settle for a few days then took off 3 to 4 litres of the clear water from the settled slurry.  Then the brew was stirred to the consistency single cream (a finger dipped into the slurry given an even coating).

Two previously made test tiles, Biscuit fired to 1015°C in my electric kiln, were coated in Five Buddies slurry, one thickly the other thinly.  When dry these were placed in the kiln with other ware glazed with several colours then fired to 1285°C.  A day to fire, a day to cool down makes for a somewhat agitated potter.

Opening a Glost fired kiln is a mixture of extreme emotions; anticipation both optimistic and pessimistic, excitement and disappointment are simultaneous.  The order for a special occasion has either cracked, bloated, crawled; pinholed or turned out really well, paranoia?  Maybe.  What about the Five Buddies Sink Glaze?  For once doubts were cast aside; the tiles were now a rich slightly metallic deep plum red, shiny, textured and very opaque.  Thickness of the coating made very little difference.  Test successful so now on to dipping some pots.  I chose to use mugs, as these were likely to sell (more optimism).  So my next Glost firing included four mugs coated like sieving our oversuits in dig spoil refined by sieving but needing no additions of fritting agents.  The only extra was a lip dip in a shiny white glaze due to the rather course texture of the main glaze, unpleasant when drinking. Once again it was with trepidation I opened the kiln to find my fears were unfounded, the mugs were all I had hoped for.  The lip dip made an interesting colour and took away any sharp texture making use comfortable.  I gave one to J'Rat so that others may see it in use at Bat Products and express interest in owning one or more.  Martin Torbett on seeing the prototypes ordered six, I offered mugs for sale at the Caver's Fair in July, single handled and two handled cider mugs with some success.  If you haven't got one yet don't despair.  I have some left and can take orders for customised pots at popular prices (popular to me that is!).

Glossary:

Glaze: An impervious surface on a pot, not necessarily shiny.

Glost Firing: Firing the glaze onto the pot.

Biscuit Firing: A low temperature firing which turns clay to pottery/non impervious such as flowerpots etc.

Fritting Agents: Materials such as sand, which adds silica to clays and glazes to give glass content.