Developed in the 1930's, Bausch & Lomb was the original manufacturer of the TAPPI Opacity instrument. TAPPI T 425 was written around this instrument which was developed to measure of the hiding power of a material. In most applications, it is a sheet of paper or a single layer of flexible packaging. The initial idea was to compare the reflectance of a single sheet backed with a black body to the reflectance of a single sheet backed with a white backing with the highest known reflectance.
Magnesium oxide was the highest reflectance across the visible spectrum at the time of the development of brightness and opacity. Therefore, the reflectance of magnesium oxide was set as the 100% point on the brightness scale in the 1930's. Likewise, magnesium oxide was going to be used as the white backing for the measurement of opacity. The problem was that magnesium oxide was very unstable (it yellowed quickly when exposed to air) and it was a chalky material which would be affected when coming into intimate contact with paper. The solution was to place a piece of glass between the magnesium oxide and the paper. Magnesium oxide was replace with magnesium carbonate which was more stable. These two changes led to a white body with a reflectance that was 89% of the reflectance of magnesium oxide.
|BNL-2 Opacimeter (2 piece design)|
Bausch & Lomb sold the rights to the opacimeter to Diano Corporation (Woburn, MA, USA) around 1970. Diano also purchased the rights to the GE Brightness design originated by Kimberly-Clark and General Electric (the basis for TAPPI T 452) from Martin Sweets Company (Louisville, KY, USA).
Jerry Popson was an employee of both Martin Sweets and Diano. He was involved in design and sales of the equipment. He started Technidyne Corporation in 1974 with the opacimeter and brightness tester. The BNL-2 Opacimeter™ was manufactured by Technidyne from 1978 to 1987. The BNL-3 Opacimeter™ was manufactured by Technidyne from 1987 to 2016.
|TEST/Plus™ Opacity from Technidyne|