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This is Plainsman BGP, a terra cotta, mixed with 30% dolomite. Note the "DSHR" column in the SHAB test data (third last column): The drying shrinkage still averages over 7% even with the 30% dolomite, so BGP is very plastic. Notice the "FSHR" (fired shrinkage) column, it is negative for the first five test bars fired at cone 05-01, that means the bars grew in size! But notice the shrinkage hits 0% at cone 1 (bar #6). By cone 2 the trend has reversed to 0.3% shrinkage. The #6 bar is appears to be vitrifying, the color is darkening and it is strong. But notice the last "ABS" column (water absorption), it is 18.7%! This body was intended as a high-porosity ceramic at the lower ranges (it has 25% porosity at cone 05), but the dolomite is also slowing the densification as it goes through the vitrification process. Without the dolomite the top bar would be melting! By cone 1 its firing shrinkage would be 7% and the porosity would be zero. Is this technique practical? Yup! The entire monoporosa wall tile industry is based on it!
Articles |
Monoporosa or Single Fired Wall Tiles
A history, technical description of the process and body and glaze materials overview of the monoporosa single fire glazed wall tile process from the man who invented it. |
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Glossary |
Firing Shrinkage
During drying, clay particles draw together and shrinkage occurs. During firing the matrix densifies and shrinkage continues. More vitreous bodies shrink more. |
Materials |
Dolomite
An inexpensive source of MgO and CaO for ceramic glazes, also a highly refractory material when fired in the absence of reactant fluxes. |
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