What microscopes are used in the Asbestos Industry?
The asbestos industry uses two different types of microscopes to COUNT and IDENTIFY fibres.
Firstly, there is the Counting Microscope. How does it work?
Counting microscopes are fitted with Phase Contrast. This is only on the 10x and 40x objectives. They must have 12.5x or 15x eyepieces allowing a mininum of 500x magnification using the 40x objective. One of the eyepieces is fiited with a special Walton & Beckett Graticule.
The Walton and Beckett graticule is used for counting fibrous dust (e.g. asbestos or glass fibres) and is particularly useful where the majority of fibres to be counted are shorter than 5 micron. The circle is divided into four by two diametrical lines scaled in units of 5 and 3 microns respectively. 3 and 5 mincrons are the critical measurements of fibre lengths used in fibre counting. Unlike the usual globes of other particle graticules, the Walton and Beckett has a series of shapes to compare objects with. These shapes have been designed for comparison with fibres, especially since they incorporate an aspect ratio of 3:1 or 5:1 essential for such analysis.
To use phase contrast, the illumination must be aligned. An element in the condenser is aligned with an element in the phase contrast lens. This usually involves sliding a component into the light path or rotating a condenser turret. The elements are either lined up in a fixed position or are adjusted by the observer until the phase effect is optimized. Generally, more light is needed for phase contrast than for corresponding bright field viewing, since the technique is based on a diminishment of brightness of most objects.
Secondly, there are Identification Microscopes. How do they work?
This is basically a polarising microscope. The main difference on these microscopes is the stage. Instead of a traditional x/y mechanical stage, they are circular and can rotate 360 degrees. Above and below the stage are polarising filters. Again, it is possible to rotate the filters 360 degrees. Most microscopes are fitted with standard 10x and 40x Objectives.
When the instrument is set up correctly, it can be used as a normal brightfield microscope. The microscope uses two polarizers, one on either side of the specimen, positioned perpendicular to each other so that only light that passes through the specimen reaches the eyepiece. Light is polarized in one plane as it passes through the first filter and reaches the specimen. Regularly-spaced, patterned or crystalline portions of the specimen rotate the light that passes through. Some of this rotated light passes through the second polarizing filter, so these regularly spaced areas show up bright against a black background. Above are some examples of asbestos fibres using this technique.
Mazurek Optical Services Ltd started trading in April 2002. Stephen Mazurek and Jane Fletcher had both come from a microscopy background, Stephen being Service Manager and Jane being Office Manager of there former employer. The companies prime business was microscope servicing and repairs but it wasn’t long before our sales division grew after Mazurek became a Meiji Techno approved dealer. After going from strength to stength over the following 4 years it was time for the company to expand further.
In January 2006. Mazurek merged with another microscope company, PBA Microscopes of York. Norman Scott came in to the company to strengthen the servicing division. This immediatey doubled our client database and worked better for all of our customers geographically.
Mazurek are still expanding its client base. Stephen now manages the sales division, demonstrating our range of microscopes, camera’s and accessories, while Norman manages the day to day running of the servicing division.
Since the beginning of 2007, we have employed more engineers and expanded our range of products.