Vince Pitelka on sat 13 apr 96
Tom -
I wasn't online a year ago to hear the discussion about hydrometers, but I am
disturbed by the conclusion that floating hydrometers are not accurate, and the
possible misinterpretation of that conclusion by many who could greatly benefit
from using a glaze hydrometer. It is certainly true that a particular specific
gravity of one glaze, measured with a standard glaze hydrometer, cannot be
expected to work with another glaze, for the reasons mentioned. But for 16
years or so I have used a hydrometer to standardize glaze mixing - once I have
a specific gravity reading from a glaze that performs well, I can use that
reading to attain the same performance from subsequent batches of the same
glaze. It has been a tremendous help. Also, I now use a great deal of terra
sigillatas with my students, and I cannot imagine making them without my
hydrometer. I have achieved super-refined terra sigs which give a high-luster
in one coating and a single polishing, and the only way I am able to do this
with consistency is by very carefully measuring specific gravity with a
floating hydrometer in the initial mix before settling, and in the final mix to
be applied to the wares.
I guess what all this means is that the hydrometer reading is relative rather
than absolute, but when used to obtain similar results in a given batch-recipe,
once the ideal specific gravity for that recipe is known, it can be extremely
helpful.
- Vince
Vince Pitelka - wkp0067@tntech.edu
Appalachian Center for Crafts - Tennessee Technological University
Smithville, TN
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