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Clay Questions

Clay Questions

    What's the recommended firing process for clay and glazes?

    We generally recommend biscuit firing at 1000-1060C then following with a glaze firing to a...
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    What is the optimum firing rate to use?

    The optimum rate depends upon the thickness of the pots and clay type e.g. thin...
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    What's the maximum firing temperature for your clay bodies?

    This is approximately indicated by the vitrification point stated for each clay in our catalogue...
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    What is the ideal bisque firing temperature to use?

    The biscuit firing temperature that is chosen should either give the clay sufficient strength to...
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    Is a bisque firing necessary, or can I skip straight to glaze firing?

    Both the clay and glaze, particularly in the case of stoneware and porcelain, can be...
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    How can I make my pieces frostproof?

    Pottery is damaged when moisture that has been absorbed into the clay, freezes. Water expands...
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    What can I do if my clay has frozen?

    What can I do if my clay has frozen? The effect of freezing on clay...
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    I've fired my vases to vitrification so why is moisture still seeping through them?

    In the vitrification process the free silica and feldspathoids in the clay melt and flow...
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    What does your "recommended firing range" mean?

    The "recommended firing range" is the temperature range over which we expect the clay to...
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    Can I mix two or more clays together?

    In the majority of cases the answer to this question is yes, it is possible...
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    Why is my fired ware weak and brittle?

    This is normally a very good indication that the ware is underfired. All fired clays...
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    What’s causing the white bloom on my red clay pieces?

    The white bloom that sometimes develops on the surface of unfired red clay bodies is...
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    How can I improve 'toasting' in my fired clay body?

    Toasting in the unglazed clay surface can be encouraged by having a thicker cross section...
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    Why doesn't Potclays have a system in place to accept clay bags for refilling?

    Logistical Difficulties: All our clays are bagged straight from the pug to optimise condition and...
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    When should I clean out my sedimentation tank?

    Sedimentation tanks should be cleaned out regularly to prevent the sediment level building up (and...
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    Why is my bag of red clay so stiff compared with other types of clay?

    Potclays red clay bodies are manufactured to a hardness (NGK reading) of between 6-8, tested...
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    Does "Bisque" mean the same thing as "Biscuit"?

    Although today these terms are practically interchangeable in the description of the first firing, they...
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    What is the difference between stoneware and earthenware?

    The most obvious difference between stoneware and earthenware is temperature, stoneware pots are fired above...
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    Does Potclays clay contain sulphur?

    This is a question we are asked quite often. There are trace amounts of sulphur...
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    How should I safely handle powdered ceramic materials?

    Dust from powdered ceramic raw materials, glazes, slips and clay can cause health problems if...
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    Can I use items made from your flecked clays in the microwave? 

    Yes - the fleck in our clays is created by an iron-bearing compound which is...
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    How much clay do I need for my mural?

    We have a handy calculator here on our Technical Information page - direct download link...
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    My clay is too hard - how can I soften it?

    Clay can be softened further using the popular Evolution Stoneware approach (see video below). A...
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    What is "Magic Water" and how do I use it?

    Magic Water uses deflocculants as is used making casting slips where it allows clay particles...
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