In 1983, pre-Internet and in a year that saw early public access to mobile phones and the first incarnation of Microsoft Word, Graham Rideal set about applying his unique scientific experience and expertise to the development of glass microsphere standards whose hallmark is absolute reliability and traceability.
‘When I started working in this field, although single size latex microspheres had been used to calibrate particle sizing instruments for some time, their narrow particle size distribution meant that they were less effective for accurately measuring wide dynamic ranges,’ he explains. ‘They were also very expensive, had a short life span and could be unstable under wide temperature fluctuations. Although a range of crushed quartz was available through the European Community (BCR), the material’s irregular shape and optical inhomogeneity were providing equivocal results for some of the developing laser diffraction techniques.
‘There appeared to be a gap in the market for robust polydisperse microsphere standards that could be used for calibrating any particle sizing instrument from the humble sieve to the latest laser diffraction particle sizing instruments.’
In the early Eighties, there were comparatively few automated particle-sizing techniques, adds Rideal. ‘Electrozone techniques such as the Coulter Counter were well established along with some sedimentation devices, but laser diffraction was still in its infancy and there were only one or two very basic automated image analysers. Sieve analysis still played a very significant role.’