Glossmeter

Many industries use glossmeters in their quality control to measure the gloss of products to ensure consistency in their manufacturing processes.

The Ingersoll "Glarimeter", the earliest known instrument developed for gloss measurement, was based on the principle that light is polarised in specular reflection.

The instrument employed incident and viewing angles of 57.5° and used a contrast method to subtract the specular component from the total reflection using a polarising element.

Early work in 1925 by A. H. Pfund[3] led to the development of a variable angle "glossimeter" to measure specular gloss which was later patented in 1932.

In 1937 Hunter, as part of a research project for the U.S. National Bureau of Standards, produced a paper on the methods of determining gloss.

In this paper he discussed instruments that were available at the time (including the ones mentioned previously) in relation to the classification of six different types of gloss.

The ASTM Method states that the illumination should be defined such that the source-detector combination is spectrally corrected to give the CIE luminous efficiency, V(?

The instruments are calibrated using reference standards that are usually made from highly polished, plane, black glass with a refractive index of 1.567 for the Sodium D line, and these are assigned a gloss value of 100 for each geometry.

The measurement results of a glossmeter are related to the amount of reflected light from a black glass standard with a defined refractive index.

An angle of 45° is specified for the measurement of ceramics, films, textiles and anodised aluminium, whilst 75° is specified for paper and printed materials.

For other materials, highly reflective in appearance (mirrors, plated / raw metal components), higher values can be achieved reaching 2000 Gloss Units.

For these applications it is common to use percent reflection of incident light rather than gloss units Each glossmeter is set up by the manufacturer to be linear throughout its measuring range by calibrating to a set of master calibration tiles traceable to BAM Federal Institute for Materials Research or similar organisations.

If a calibration standard becomes permanently scratched or damaged at any time it will require immediate recalibration or replacement as the glossmeter may give incorrect readings.

The glossmeter is adopted by many industries, from paper mills to automotive and is used at each stage of the manufacturing process from goods receipt through to final inspection.