Photography: SCHUPP® Ceramics, small picture: before pre-firing, large picture: after pre-firing
Originally PTCR has been developed for critical firing processes to document the heat treatment under air atmosphere. However, PTCRs are suitable for different kiln atmospheres or even vacuum conditions.
It is necessary to pre-fire the PTCR before using it under specific atmospheres or vacuum.
Generally, it can be stated that, under vacuum conditions and reductive atmospheres like N2/H2 mixtures, the rings must be thermally-treated under air atmosphere before using it to burn out the organic binder. If this is not done properly, the organic material will not disappear as CO2, but will decompose to carbon. This carbon, left behind in the ring, will inhibit the shrinkage of the ring, resulting in a lower reference temperature (RT) reading than expected. Under vacuum conditions, the carbon may even precipitate on the kiln wall and contaminate the kiln. This is avoided by the de-binding process as described above. If you want to use PTCR in fast firing cycles, pre-treating is also recommended.
During the pre-firing process the organic coloring pigment will also be burned out. Therefore, the rings will lose their original color and appear white or gray after pre-firing, depending on the ring type. PTCR ZTH, MTH and HTH are already pre-treated and do not need to be pre-fired again!
Would you like to pre-fire PTCR yourself, please use the ring specific pre-firing curves and parameters according to our manual under point 5.7. If you are not sure whether a pre-treatment of PTCR is necessary, for your process conditions, please contact us at any time!
We will gladly manage the pre-firing process for you. Please feel free to contact us!