GLAZE GROUP MEETING

12^th October 2004

The first topic discussed was vitreous/reactive slips.  Di had brought along an egg made of T material, studded with rice, bisqued to 1000° C with an application of a magnesia matt glaze   and an orange red iron glaze on top (fired to 1200° C).  Result was a pale russet-brown with deeper colour in the indentations where rice had burned out.   No signs of any reaction, so a disappointing experiment.  Rose had used a white stoneware engobe on bisqued porcelain: flint 10; potash feldspar 10; china clay 10; ball clay 5; nepheline syenite 5 + 0.75% copper oxide with Charles’s artificial ash glaze randomly over the top.   Where engobe had not been covered, a cratered bubbly surface had resulted, a smooth varied green where glaze and engobe had fused.  Fired to 1220° C in electric kiln.

Artificial Wood Ash glaze – Di had not yet received any feedback following her letter to Ceramic Review.

Raw Glazing – was discussed with Alison showing her lovely porcelain examples using Takichi Yasuda’s base glaze with varying oxides added.  All samples had been fired in the region of 1260°° C – 1280 C°.  It was felt that the best state to apply glaze to raw pieces was when leather hard (or when fully dried for porcelain).  Charles handed out a modified recipe for his artificial wood ash glaze containing 20.6% Hymod SM ball clay for further experimenting within the group.

Crazing – Rob Dunster had e-mailed Charles regarding this problem.  The remedy of adding silica to the glaze could alter the glaze’s character or totally unbalance the recipe. An alternative possible approach might be to lower the expansion of the glaze by replacing some of its constituent oxides with others having lower rates of expansion.  it was felt that using a higher silica body would add to the crazing problem.

Food safety – Alison was waiting for details from a test glaze company in Stoke on Trent.  She will report back to the group next time.  It was felt that the Government Health and Safety advice was limited and not very forthcoming.  Particular concern was the use of cadmium, barium and copper in glaze.

Pit Firing – Group praised Mike’s write up of the day.  Iron sulphate had given beautiful yellowy/orange effects  One SCG member had bought hers in Holland and UK sources will be investigated.

Oriental glazes – Mike Bailey’s latest book was studied with most of the recipes needing reduction firing.  As most of the group have electric kilns saggars will be tried using moth balls, graphite, silicon carbide and paper clay etc for local reduction  The group will try John Britt’s oil spot tenmoku – potash feldspar 25; soda feldspar 35; ferro frit 3110; china clay 15; dolomite 5; talc 5; flint or quartz 8; bentonite 2; red iron oxide 6.  Apply thick and fire to cone 8/9 without a soak.

Crystalline glazes – Rose will talk on these next time.

Newsletter – It was much appreciated that the Newsletter can again be accessed on the Web but it was noted only the Glaze Group minutes can be read.

Finally Mike showed his latest ongoing experiments with ground, fired ball clay, soda feldspar and resin.   Different oxides had then been added and his glaze: whiting 30; quartz 30; china clay 30; titanium dioxide 10; zinc 2 on top.  The result was a very pronounced speckly smooth surface of contrasting light and dark blue speckles.

Glaze Group meetings are held at the home of Diana Carter on the second Tuesday of every other month. The next meetings will be on 14^th December and 11^th January 2005. Time in future will be at 12 noon instead of 1.00 pm.  Bring contribution to a potter’s lunch and please let Charles Stileman (01794 340193) or Diana Carter (01962 777297) know if you are coming.