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Glass is a unique material to measure as the glass itself is similar to honey – its viscosity changes dramatically with a change in temperature. Temperature is critical for the forming process because, in this temperature range (about 2000°F / 1100°C), the viscosity of glass changes by 30% with a temperature change of only 1°C. Like honey, when glass is warm it can flow like water and when it is cold it is solid as a rock. As it is cooled from its liquid state, it gradually becomes thicker and thicker and it resists flow gradually more and more. As a result, for many forming processes, the process is often controlled to a fraction of a degree.

Williamson Advantages

For the glass industry, Williamson offers several unique solutions for these challenging measurement conditions.

Flames and Combustion Gases

Because the glass is heated using flames, the most universally significant Williamson advantage is the ability to view clearly through flames, reflected images of flames and combustion gases without interference. Williamson offers the only short-wavelength pyrometers able to view clearly through flames and the only DW and MW pyrometers with ESP filtering to avoid intermittent flame interference.


For the glass container and pressed and blown glass market sectors, glass molds and plungers are lubricated with a mixture of oil and kerosene, and Williamson pyrometers are better able to tolerate oil compared to other brands. Because of Williamson’s narrow-band wavelength sets, Williamson pyrometers are able to view clearly through thin films of oil without interference.

Specialty Products

Williamson has developed a number of specialty products specifically for the glass industry.

Fiberglass Batting Hot Slug Detector: This one-of-a-kind pyrometer is used to detect hot slugs of glass buried within the fiberglass batting and is used to prevent warehouse fires caused by these embedded hot slugs.

Safety Glass Lamination: The Williamson model SW-29-08 uses the unique 29 wavelength set. This wavelength views clearly through glass, but not through the plastic film used to produce safety glass. This is the only commercial pyrometer able to monitor the temperature of the plastic film during the lamination of safety glass.

Mold and Plunger: The Williamson Multi-Wavelength MW-10 technology represents the only pyrometer able to produce an accurate measure of temperature for both new and aged molds and plungers. When combined with Williamson’s patented ESP Filtering, a continuous measure of an intermittent target is obtained, and intermittent interference from flames and other unintended target materials is eliminated.

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