How to choose a Gloss Meter?

How to choose a Gloss Meter?

What is a Gloss Meter?

A gloss meter (also named glossmeter, gloss gauge or mirror gloss meter) is an instrument which is used to measure specular reflection gloss of a surface. It is mainly used for paint, plastic, print, metal, ceramic, building material, leather and other industries which need measure gloss. Gloss meter can be separated into two type single angle and triple angles (triple angles gloss meter is called multi-angles gloss meter). Our model number is CS-300 (single angle) and CS-380 (triple angles).

History of Gloss Meter

Of the many internationally recorded publications relating to gloss measurement, the earliest recorded studies (perceived and instrumental) are attributed to Ingersoll, who in 1914 developed a means to measure the glare of paper. 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. Ingersoll successfully applied for and patented this instrument a few years later in 1917.

In 1922 Jones, during his study of gloss of photographic papers using goniophotometry, developed a glossmeter based on his research, which provided closer correlation to gloss ratings assigned by visual evaluation. Jones’ glossmeter used a geometric configuration of 45°/0°/45° whereby the surface was illuminated at 45° and two incident reflective angles measured and compared at 0° (diffuse reflectance) and 45° (diffuse plus specular reflectance). Jones was the first to emphasize the importance of using goniophotometric measurements in studies of gloss.

Early work in 1925 by Pfund led to the development of a variable angle “glossimeter” to measure specular gloss which was later patented in 1932. Pfund’s instrument, allowed the angle of measurement to be varied, but maintained the angle of view to the angle of illumination. Reflected light was measured using a pyrometer lamp as a photometer. The ‘glossimeter’ was the first to use black glass standards as a basis for reflectance setting. As the angle was variable this instrument could also be used for the measurement of sheen or specular gloss at near grazing angles.

During this time, growing interest in this field resulted in a number of similar studies by other individuals each having their own method for gloss measurement, most of which published as technical articles in scientific journals of that time. A few of these also resulted in patents.

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. In this paper Hunter also detailed the general requirements for a standardised glossmeter. Standardisation in gloss measurement was led by Hunter and ASTM (American Society for Testing and Materials) who produced ASTM D523 Standard test method for specular gloss in 1939. This incorporated a method for measuring gloss at a specular angle of 60°. Later editions of the Standard (1951) included methods for measuring at 20° (high gloss) and 85° (matt, or low, gloss). ASTM has a number of other gloss-related standards designed for application in specific industries.

In the paint industry, measurements of specular gloss are made according to International Standard ISO 2813. This standard is equivalent to national standards ASTM D523 (United States), BS 3900, Part 5 (United Kingdom); DIN 67530 (Germany), NFT 30-064 (France), AS 1580 (Australia), JIS Z8741 (Japan).

Gloss Meter Working Theory

As shown in the figure, the measuring head of the instrument consists of a transmitter and a receiver, which consists of an LED light source and lenses, which produce a desired incident beam. The receiver is composed by a lens and a photosensitive element for receiving a cone beam reflected from the surface of the sample.

Mirror gloss is the relative measurement for the mirror gloss. The reference standard is a black glass with a refractive index np = 1.567, assuming that the plane is subjected to mirror reflection of the natural beam by the plane in the ideal polished state, and the gloss value at this time is defined as 100.0 gloss units. Gloss board is divided into high, medium and low three according to the gloss value. The high gloss board is made by black optical glass or other material. The medium and low gloss plates are made by glazed ceramic or black optical glass. The gloss meter measures the gloss of the sample according to light reflection principle. That is, the sample is irradiated with a predetermined incident angle and a prescribed light beam to obtain reflected light in the direction of the mirror reflection angle.

What is Gloss?

Gloss is an aspect of the visual perception of objects.

Gloss is the attribute of surfaces that causes them to have shiny or lustrous, metallic or matte appearances.

Gloss is a visual impression that is caused when a surface is evaluated. The more direct light is reflected, the more obvious will be the impression of gloss.

Gloss effects are based on the interaction of light with the physical properties of the sample surface. The other influencing component is the physiological evaluation scale. The human eye is still the best tool to evaluate gloss differences. However, the visual surface control is insufficient, because evaluation conditions are not clearly defined, and people see and judge differently.

In addition, the subjective perception of appearance is dependent on the personal experience: what is glossy for a paper manufacturer might be dull for an automotive maker. Gloss is measured by focusing on the reflected image and not by focusing on the surface. Eyesight and mood have a decisive role in the visual judgment. Also, important is what our eye is focused on. We evaluate a surface by focusing our eye on a reflected image of a light source. In order to guarantee a reliable and practical quality assurance it is necessary to define appearance with objective, measurable criteria. Accurate characterization of appearance does not only help to control quality, but improves quality and optimizes manufacturing processes.

What difference in gloss can a human see ?

If two different coatings are measured, what number of gloss units would be detectable by the human eye, how many units would be perceived as significantly different?

When measuring at 60 Degrees these detectable differences depend on the gloss level of the sample, for instance 3.0 GU difference measured on a very matte surface (perhaps 5GU), would be seen by the human eye but on a higher gloss coating (perhaps 60 GU) the difference would be very difficult to notice.

The only way that you can determine tolerances for your products would be experimentally, perhaps preparing printed samples at different gloss levels that you can show to end users of your coatings or internal “experts”.

The other option is to change to a 20/60/85 degree instrument, the 85 degree glossmeter is more sensitive to differences in gloss below 10 GU @ 60° and the 20 Degrees has higher resolution on high gloss coatings (above 70 GU @ 60°). The advantage of using the three angles is that there is more equality to the gloss differences, in our experience a gloss difference of 5 GU, when measured with the correct geometry is just visible to a trained observer.

Why Measure Gloss?

Gloss is an aspect of the visual perception of objects that is as important as color when considering the psychological impact of products on a consumer. In other words, “Gloss Sells” Gloss has been defined as the attribute of a surfaces that causes it to have a shiny or lustrous, metallic appearance.

The gloss of a surface can be greatly influenced by a number of factors, for example the smoothness achieved during polishing, the amount and type of coating applied or the quality of the substrate. Manufacturers design their products to have maximum appeal. Such examples are; highly reflective car body panels, glossy magazine covers or satin black designer furniture. Now what happens when products all of a sudden look different? Customers see this as a defect, or poor quality. Using a glossmeter and having good quality control practices eliminates this variable as a problem.

It is important therefore that gloss levels be consistent on every product or across different batches of products. Gloss can also be a measure of the quality of a surface, for instance a drop in the gloss of a coated surface may indicate problems with its cure- leading to other failures such as poor adhesion or lack of protection for the coated surface.

It is for these reasons that many manufacturing industries monitor the gloss of their products, from cars, printing and furniture to food, pharmaceuticals and consumer electronics. We also have Gloss Sensors used in process for real time gloss measurement. Please call us at 1-866-462-6832 to discuss the inline application.

How is Gloss Measured?

In case of transparent materials the measurement value can be increased due to multiple reflections in the bulk of the material. Due to the high reflection capabilities of metals values of up to 2000 GU can be reached. For these applications it is common to document the measurement results in % reflection of the illuminated light. Glossmeters and their handling procedures had to be internationally specified to allow comparison of measurement values. The angle of illumination is of high influence. In order to obtain a clear differentiation over the complete measurement range from high gloss to matte, 3 different geometries, i.e. 3 different ranges, were defined using a 60° glossmeter.

Gloss Range with 60° Gloss Meter	Measure With:
If Semi Gloss – 10 to 70 GU	60 °
If High Gloss > 70 GU	20 °
If Low Gloss < 10 GU	85 °

In this case study, 13 samples were visually ranked from matte to high gloss and measured with the 3 specified geometries. In the steep slopes of the curves the differences between the samples can be clearly measured, while in the flat part the measurement geometry no longer correlates with the visual. Gloss measurement for any application, whether you are dealing with specific applications or need a universal solution for high to matte gloss samples, www.gloss-meters.com offers a complete line of glossmeters.

How to choose a Gloss Meter?

Gloss measurement is based on the amount of light reflected on the surface relative to a polished glass reference standard, measured in Gloss Units (GU). The amount of light that is reflected on the surface is dependent on the angle of incidence and the properties of the surface.

Gloss is categorised as either matt, semi or high gloss. In order to determine the most appropriate measurement angle start with a glossmeter set at a 60° angle of incidence.

Source: China Gloss Meter Manufacturer – www.spectrumgfa.com
www.spectrumgfa.com is one of the leading china Colorimeter & Spectrophotometer Manufacturer, with professional factory. We focus on the colorimeters, spectrophotometers, haze meters, gloss meters and spectral analysis instruments research and development, manufacturing, sales and service since the company been established. Our products is widely used on Painting,textile,plastic industry,food,building material and other products. 
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References:

• https://en.wikipedia.org/wiki/Glossmeter