Glaze Group Meeting

12th December 2006

Charles opened the meeting with further discussion on his Artificial Ash Glaze.  All three of his pots had lovely smooth surface and we discussed why a very good Jun had been achieved on the inside of each pot particularly.  The right thickness of glaze was paramount, it was evident that where the glaze had accumulated in the base of the pot, more blue was visible. Clay body was important too, a quote from Mike Bailey suggested 'the colour is at its best over iron bearing bodies and is an optical effect, brought about by the scattering of light at the blue end of the spectrum whilst the remainder of wavelenghts of visible light are absorbed'.

Di had brought along her latest samples featuring blue glazes from Mike Bailey's Cone 6 book and one of his Jun glaze recipes.  The clay used for all samples was Scarva Earthstone, fired at Cone 6, and results were variable.  Good smooth blues were obtained using 5% tin and 2% cobalt oxide in an alumina semi-matt glaze, but 4% cobalt oxide and 5% titanium in a transparent glaze gave little blue.  It was the group's opinion that it was due to too thin an application.  Her Jun glaze also had only a hint of blue, again probably too thinly applied.  Discussion followed with tips on how to get the right consistency for glaze.  Removing excess water with hydrometers, sponges before stirring the glaze is sensible, testing first by dipping in samples to see how well the bisque takes up the glaze, Charles dampens his bisque ware just before applying the glaze, which stops some of the water being absorbed into the pot itself leaving a good layer of glaze on the surface.  Also a thicker pot will need a thicker layer of glaze Mike suggested.

Mike also had plenty of sample tiles having experimented on various matt glazes.  He had achieved good black, white, grey and blues, finding that a percentage of tin gave the bluey white.

The meeting ended with discussing our kilns, and their respective maintenance problems.  Replacement of elements varied in my case firing crystalline glazes which require an amount of soaking time longer than regular glaze recipes.  I have replaced my own elements three times in 10 years.  Clive Shellard (Bath Instruments) has given quick advice and delivery on parts and elements and is highly recommended by Charles and myself. 

The next Glaze Group Meeting will be at Diana Carter's home on the second Tuesday of February 2007 at noon.  Everyone is welcome.  A contribution towards a light lunch will  be appreciated.  Let Diana Carter (01962 777297) know if you plan to attend.