Are all glazed fired at the same temp?
  

   
No, the temperature at which the glazes are fired depends on the ingrediants in the glaze.  The chemicals in the glaze have to have time to develop and bond with each other so they become hard and wont chip off of the piece. 
     There are low, medium, and high firing glazes and there are low and high firing clays.  Low fire glazes are formulated to be fired from cones 015-1 (1479 F to 2109 F).  There is a larger variety of color choices for low fire than high fire glazes.  Most of the glazes provide smooth and bright colors.
     Medium fire glazes are formulated to be fired from cone 2 to 7 (2124 F to 2264 F).  One of the reasons medium fired glazes were made was because a lot of the electric kilns on the market do not heat above cone 6 or 8.
     High fire glazes are formulated to be fired from cone 8 to 13 (2305 F to 2455 F).  High fire glazes, unlike low fire glazes, bond with the clay body and create a layer between the clay and glaze known as a buffer layer.  One advantage to a high fire clay is that it protects better against peeling and other stresses.  Since the glaze and clay interact with each other more blotches and color changes can be produced.  
     If a high firing glaze was placed on a low firing clay the glaze wouldn't have time to bond and therefore would chip off.  The clay and glaze that is applied to it also has to have the same shrinkage rate otherwise you would have a glaze that fit on a pot like a baggy pair of jeans. 
Made by Jan Cannon
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