The task of setting a particle size specification for a material requires knowledge
of which technique will be used for the analysis and how size affects product
performance. Sources of error must be investigated and incorporated into the final
specification. Be aware that, in general, different particle sizing techniques will
produce different results for a variety of reasons including: the physical property
being measured, the algorithm used, the basis of the distribution (number,
volume, etc.) and the dynamic range of the instrument. Therefore, a specification
based on using laser diffraction is not easily compared to expectations from other
techniques such as particle counting or sieving. One exception to this rule is the
ability of dymanic image analysis to match sieve results.
Attempting to reproduce PSD results to investigate whether a material is indeed
within a stated specification requires detailed knowledge of how the measurement
was acquired including variables such as the refractive index, sampling
procedure, sample preparation, amount and power of ultrasound, etc. This
detailed information is almost never part of a published specification and would
require additional communications between the multiple parties involved.
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