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Glaze Dilema - Old vs New - Glazes: Article or Project


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In the late nineties, the ceramic world was rocked when the EPA got involved requiring ceramic glazes and clays become safer to use. Manufacturers were scrambling to create new formulae for their glazes and discontinue their current product line.

Emphasis of the EPA action was toward industrial manufacturers spraying glazes, which if done in excess did cause major health concerns; however their enforcement had major consequence on the casual ceramist. One of the major concerns was that many of the older glazes contained Cadmium and Lead.

It was in the late nineties, when the Ceramic paint companies began changing their formulae, some successfully and other not-so effective. Colors ceramists knew and loved went by the wayside. The replacements in most cases were nowhere near as vibrant, some colors could not be matched and the resulting products had many issues. By the year 2007, the date all companies were to comply, there had been many changes - some good, some not-so-good and some pure ugly (and difficult to work with).

The companies are still working diligently to make new colors and new products and are coming out with some great ones-their color pallets are ever changing. But what happened to all the old glazes??

Those old products often show up on the secondary market and with them questions as to their safety and can they still be used. As an old time ceramist, I am an advocate of, ‘If you can find a way, use it – Never toss it’. Of course, I do want folks to be safe and I want their final products safe for use. However, with my ‘limited’ knowledge of the history on why changes were made, I feel with proper care, they are still ‘safe’ to use

Having done some research on the glazes it seems that coming with the old glazes are some dos and don’ts regarding their use.

1) Not all old glazes are compatible with new glazes.
2) If spraying the glaze, use protective mask and good ventilation.
3) READ the labels and/or old literature to find firing requirements, food safety, overglaze/glaze compatibility. Food safety does change- it's based on the amount of leaching . You need to test lead/cadmium release with lead strips if you are using leaded/cadmium glazes on utility items.
4) Make a test chip – old glazes may not retain their color stability due to past storage conditions etc.
5) DO NOT fire copper glazes with the leaded glazes
6) Dried out glazes can be refurbished or used for other purposes. To recondition use Glaze Gum or Brushing Media and a small amount of water (distilled is best). Available from Amaco as well as other product manufacturers.
7) DO NOT mix leaded and unleaded in great quantities on the same piece as they have different firing coefficients and will probably split the piece.
8) There are also creative uses for the old and dried out glazes such as crushing and making your own crystal glazes by adding the bits to another liquid glaze (check compatibility)
9) Some people claim that the leaded glazes should never be fired in the same kiln as other products because it will contaminate walls and elements. We have found NO research giving verifiable evidence to this. We personally disagree with the premise.

CME would like to thank Mike Smith for his input in the writing of this article. Photo credit Lacy Davis


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