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Parent Category: Technical Articles from Journal Back Copies

Category: Technical Articles 2005

 Raymond Jackson

Effect of Grain Size

In the tests reported on so far, the enamel used was 150/- which means that only grains finer than about 0.1mm were used. Although the use of the word grain might imply spherical or oval shaped particles, examination under a microscope reveals that they are polyhedral shaped pieces of glass.

The washing process removes the extremely fine particles that can contribute to opacity in the fired enamel due to trapped air bubbles, Helwig⁵. These very small particles may also have deteriorated significantly due to attack by moisture.

It is further reported' that optimum transparent enamel clarity is achieved if particles smaller than would pass through a 325 mesh screen are also removed. This presumably is a further measure to reduce bubble entrapment. As a consequence, I now slightly changed my enamel preparation by grinding and then sieving the enamel first through the 150 mesh and then through a 325 mesh. The enamel remaining on the 325 mesh is then 150/325 material. This was washed to remove any finer dust that might otherwise remain adhering to me particles. The resulting material is smaller than 0.1mm but greater than around 0.05mm (50 microns).

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