What could be an indicator of moisture contamination in castable fireclay?

The presence of lumps in castable fireclay is a strong indicator of moisture contamination. When moisture enters the fireclay mixture, it can lead to clumping as the water causes the particles to stick together. This lumpiness can interfere with the material's performance, as it affects its ability to set and cure correctly. Properly formulated and mixed fireclay should be smooth and uniform, so any deviations from this texture—such as lumps—suggest that moisture has been introduced, potentially affecting the durability and heat resistance of the final product.

In contrast, while other factors might contribute to the quality of fireclay, such as odd smells, changes in color, or thermal conductivity, these indicators are less directly linked to moisture contamination than the presence of lumps.