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Most artists and potters want some sort of visual variegation in their glazes. The cone 6 oxidation mug on the right demonstrates several types. Opacity variation with thickness: The outer blue varies (breaks) to brown on the edges of contours where the glaze layer is thinner. Phase changes: The rutile blue color swirls within because of phase changes within the glass (zones of differing chemistry). Crystallization: The inside glaze is normally a clear amber transparent, but because these were slow cooling in the firing, iron in the glass has crystallized on the surface. Clay color: The mugs are made from a brown clay, the iron within it is bleeding into the blue and amplifying color change on thin sections.
| Glossary | 
Breaking Glaze
 A decorative effect in ceramic glazes that exploits changes in color and character in certain glazes when their thickness varies.  | 
| Glossary | 
Opacifier
 Glaze opacity refers to the degree to which it is opaque. Opacifiers are powders added to transparent ceramic glazes to make them opaque.  | 
| Glossary | 
Reactive Glazes
 In ceramics, reactive glazes have variegated surfaces that are a product of more melt fluidity and the presence of opacifiers, crystallizers and phase changers.  | 
| Glossary | 
Variegation
 Ceramic glaze variegation refers to its visual character. This is an overview of the various mechanisms to make glazes dance with color, crystals, highlights, speckles, rivulets, etc.  | 
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