Whitehouse Scientific - High Precision Glass Microspheres for Calibration Purposes

Whitehouse Scientific has been producing high precision glass microspheres for calibration purposes for over 20 years and is currently the highest-ranking European certification laboratory for primary methods of particle size analysis.

Also, having filled over 1 million bottles using a unique 100 stage spinning riffler system, we are now the world's leading manufacturer of single-shot glass microsphere standards. The references are nearly all NIST traceable range in size from 0.1 - 5,000µm and are available as single sizes or broad distribution standards. In addition to calibration, applications include filter testing, space research, nuclear fall-out studies, micro-engineering and precision spacers.

Whatever the particle sizing method, from traditional sieving to the latest laser or image analysis methods, Whitehouse Scientific has the perfect calibration standard.

Our products include:

• Polydisperse particle size standards
• Monodisperse research microspheres
• Sieve calibration standards
• Filter testing standards

POLYDISPERSE PARTICLE SIZE STANDARDS

For calibrating any method of particle size analysis, this range of glass microsphere standards has been measured by one of the largest international teams ever assembled. All the data produced is in primary form where there is a direct traceability to international standards such as NIST. The primary methods include sedimentation by gravity and centrifuge, microscopy, precision sieve analysis and the Coulter Counter method. The seven standards cover the size range from 0.1 - 2000μm and are available as single-shot bottles to minimize sampling errors during analysis.

MONIDISPERSE RESEARCH MICROSPHERES

The monodisperse glass microspheres, known as Monospheres", are the widest range of uniform glass beads available from a single source (nearly 100 sizes from 10μm to 10mm). The size distributions are extremely narrow and are used for a number of applications ranging from calibrating laser diffraction particle size analyzers to cosmic dust simulation experiments. All sizes are traceable to NIST.

SIEVE CALIBRATION STANDARDS

This is a unique method of on-site calibration of 200mm diameter test sieves. Over 30 single-shot bottles have been produced to calibrate every sieve from 20μm - 3,350μm. Each bottle contains enough microspheres to analyze over 80% of the sieve surface in about one minute with a resolution of 1μm or less for the smaller sieve apertures. All dimensions are traceable to NIST.

To calibrate a sieve is as simple as steps one, two and three.

Step one: pre-weigh the complete contents of the appropriate single-shot bottle.

Step two: shake over the surface of the sieve for one minute.

Step three: from the percentage of the standard passing, read off the mean aperture size from the calibration graph supplied.

FILTER TESTING STANDARDS

Filter testing has traditionally been done by bubble point testing or the use of Arizona test dusts. Both these methods have their limitations and problems in accurately interpreting the data produced into absolute aperture sizes.

A range of narrow distribution, high precision glass microspheres has been produced which removes the ambiguity. The microspheres either pass the filter or they do not. From the percentage passing, the mean filter aperture or pore size can be calculated. Dry powders from 20μm to over 500μm are sonically passed through the filters in under a minute. For sizes below 20μm an ultrasonic liquid based system is used.

The mean aperture size is usually determined in a minute or less, and by examining the microspheres passing the filter, the absolute retention of a filter can be determined.