Problems with our OR glaze…


We posted this on the Ceramics Daily forum, but have posted it here too, in case someone who has a good idea comes across it.  Please feel free to comment!

Our Orange Red – OR cone 6 glaze recipe is now turning out a very sad, plain brown.  The recipe is
Potash Feldspar – 46.7%
China Clay – 4%
Bentonite – 2%
Bone Ash – 15%
Lithium Carbonate – 4%
Talc – 16.9%
Fling – 11.4%

Red Iron Oxide 11.5%

Does anyone know if the make-up of any of the ingredients has changed or what might be the problem for us?  The firing is taking almost 15 hours and we are allowing a natural cooldown.  The cones (5, 6 & 7) were all totally bent.  Someone told me that this may not actually be an overfire but is possibly that the firing took too long.  May timing be the problem?  In the last firing we had one piece that was sprayed with an old mix of the glaze and it turned out ok but the new mix did not


One Response to “Problems with our OR glaze…”

  1. 1 donna

    I have a Val Cushing glaze that is Lithium based and now have had horrific problems with blistering and now it is turning brown instead of a beautiful punpkin orange with a matt surface. Today I went to use the glaxe that had been mixed in Nov. 2010 and it has rock like crystals in the glaze and they are hard ! I’m sure I will have to throw out the glaze and mix it fresh, as boiling water does not break down the crystals. I haven’t purchased new materials, or clay.

    Val Cushings satin Matt Base cone 6-7
    nepy sy 41.8
    gerstley borate 10.4
    EPK kaolin 12.5
    whiting 10.4
    lithium carb. 6.2
    flint silica 12.5
    titanium dioxide 6.2
    3% red iron ox.

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