CONSIDERING DECORATIVE GLAZES AND TEXTURAL SURFACES
• Once there was an English pottery magazine called Pottery Quarterly compiled by Murray Fieldhouse (then of Tring.) There are still a few copies on my bookshelf, fly- spotted, musty and brown at the edges. I captured my first idea for 50/50 glazes from this publication. To be precise it was 1963, Vol 8, No 29, six and sixpence, page 20 ....Bryan Newman wrote:
"I get a lot of variation from the simple recipe of:45 wood ash, 55 ball clay, plus colouring oxides. This was at 1300oC with reduction and by adding red iron oxide I produced a lovely velvety red brown. I got a lighter ochre colour by taking out the red iron oxide and adding 20 tin oxide."
• I "rounded off" the recipe to half and half (ie 50 wood ash/50 China clay) and still use it as a dry textured engobe all these years later at 1260oC in oxidisation it usually results in a very dry surface and can look very lively when oxides and stains are added to it.
• I Found another 50/50 idea on page 164 of Emanuel Cooper's"Glazes. for the Studio Potter" (Batsford) 15 years later. It just looked so easy and straightforward This is how he presented it showing another ceramic surface that consisted of virtually only two basic ingredients. I have to say that I have discontinued the use of Barium Carb. in the last few years due to warnings of dire consequences from safety experts :
Nepheline Syenite 50 Barium Carbonate 50 copper carbonate 1.5
This all eventually led to the idea that a spoon of this and a spoon of that was such an easy way of starting a new recipe and could be rushed into the kiln at the last moment before a firing began
• Always looking for an easy way ,I began to do three things that changed my whole approach to glazing.
• The first thing I started to do was to convert all my measurements to volumes using cups ,jugs, buckets, or handfuls instead of pounds, ounces, grams, or kilos!
• The second thing was to be really bold in adjusting numbers in borrowed recipes- definitely no decimal points and "rounding off" to tens.
• The third thing was to use smaller kilns and fire several times a week.
Hundreds of little clay boxes 15mm high walls on a 70mm by 50mm were filled, thickly at one end and thinly at the other, and stacked on top of each other
• This all eventually led to a really relaxed attitude towards glaze mixing and application of glaze and also led towards much experimentation. Using a smaller kiln and firing much more often resulted in quicker and more immediate learning The easy going approach spilled over into the whole area of surface treatment and removed the feeling that glazes could be overtired, under fired and go "wrong" In my my more expressive work it actually became more normal to look for and respond positively to "faults"and to enjoy the immense variety of activity that melting minerals can perform.
And so "gumboot technology" was born from a tendency to laziness in measurement, a distrust of the average and normal and a desire to use really activated surfaces on the clay.. A system of half and half , of 50/50, of equal volume quantities, spoons, cups, buckets,or gumboots of many ingredients produced very interesting results.
"What size gumboot " I hear someone ask!
Time for action------Take any of these materials and mix fifty/fifty with any other :
Borax• Frit • gerstley borate • lead bisilicate • any commercial eatherware glaze • wood ash • cement • plaster