Cone 6 Glaze Testing & Reporting

131 members

Description

Collaborate on building an online list of well documented glaze recipes, with application and firing methods. Strong photo documentation. Only glazes that are mature at cone 6 will be included.

Testing the glazes, and identifying their problems and fixing them. Also, if there are obvious issues just by looking at a glaze recipe (like high barium, insufficient clay to suspend or harden, too much feldspar (which causes crazing), too much clay (causing crawling, peeling), hard-to-get materials, non-specific materials, etc) then it needs to be fixed as part of the testing I would say.

Tony Hansen included links below to procedures for a few glaze tests that could be done. Another good one would be to appraise the rate at which it settles, how hard is the dry layer, the water content of the slurry, the viscosity, these could be measured with commonly available tools.

Links:

Thermal shock test

Melt flow test

Glaze hardness test

Glaze leaching test

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Transparent Green Glaze

by Dave Hodapp

Oct 27, 2012

Does anyone have a suggestion for a glossy, or semi-gloss, green glaze? Preferably transparent. I did locate a couple of glazes in the Insight Live Group database that might work and will try testing them; Buck Sea Green 2, Frogpond Green (with copper carb), Hesselberth Floating Green.

Thanks

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  • up

    June Perry

    You might try an oribe base for a good green. Here's one I found on the Internet. It's a Bill Van Gilder glaze.

    Oribe Green

     

    zinc oxide...................................8

    Edgar plastic kaolin...................12

    whiting.......................................24

    silica..........................................24

    custer feldspar..........................32

     

    total..........................................100

     

    add copper carbonate................4%

    bentonite....................................1%

    I don't have time to run it through my glaze software; but I'd probably up the silica by 5 and lower the kaolin by that much as a start. Oribes tend to be in the semi gloss and for porcelain you usually need more silica to avoid the crazing. If you know how to use glaze software you can tweak  the alumina and silica to give you a 10-12 ratio of silica to alumina. I wouldn't go more than 4% copper if using it on anything that could be used to serve food. Copper, even in a cone 10 glaze, won't have enough silica to deal with the more than 4% of copper and would make an unsafe glaze because the copper won't be stable, especially in the presence of any kind of acid food or liquid.

    Jan 13, 2015

  • up

    June Perry



    June Perry said:

    You might try an oribe base for a good green. Here's one I found on the Internet. It's a Bill Van Gilder glaze.

    Oribe Green

     C6 Oribe for porcelain  June Perry
     
    custer    32.09
    zinc oxide    6.22
    whiting    16.55
    epk    9.03
    silica    35.11
    talc    1.00
    copper carbonate    4
    bentonite    1

    Version 2: omit talc and up silica. Give 6.6 expansion.

       Oribes tend to be in the semi gloss and for porcelain you usually need more silica to avoid the crazing. If you know how to use glaze software you can tweak other stoneware recipes to work with porcelain. Aim to get the alumina and silica to give you a 10-12 ratio of silica to alumina for a gloss. I wouldn't go more than 4% copper if using it on anything that could be used to serve food. Copper, even in a cone 10 glaze, won't have enough silica to deal with the more than 4% of copper and would make an unsafe glaze because the copper won't be stable, especially in the presence of any kind of acid food or liquid.

    Jan 13, 2015

  • up

    June Perry

    Just add 1-2% Copper carb or copper oxide to any transparent base for a light, celadon type green. Upping the copper to 3-5% will give you darker tones. Remember that copper in the 4-5% range most probably would not be a food safe glaze because of leaching, so it's best to keep it off surfaces used for serving or storing food. 

    Jun 6, 2016