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Guide for Reliable Gloss Data

Uniform and consistent gloss are an essential quality criterion for a variety of products. Therefore, gloss needs to be objectively measured. Only what can be objectively measured, can be controlled and can be optimized which is of importance in product development as well as in production control. Especially in case of multi-component products a uniform gloss is an expression of “high quality”. Variations in gloss look like something is wrong and the end-user will perceive it as a defect. Therefore, gloss limits and tolerances are defined based on application and customer expectations.

1. Technical performance: Essential for reliable data

1.1 Repeatable gloss data

Goal is to meet the target value within a defined tolerance. Therefore, the glossmeter used should deliver repeatable measurement results i.e., excellent short- and long-term repeatability. (Fig. 1)
Otherwise, you don’t know whether the gloss change is due to a glossmeter drift or a true product variation.

1.2 Reproducible gloss data from glossmeter to glossmeter

Reproducibility is as important as Repeatability as every production is part of a supply chain process. Gloss values need be communicated and exchanged within a supply chain. Gloss levels of various production facilities or several production lines need be consistent to achieve a uniform gloss within defined tolerances. (Fig. 2)
Otherwise, a multi-component product will look like patchwork and the various component suppliers will always discuss who delivered the “part with the correct gloss level”.

1.3 Gloss measurement independent of temperature changes

Depending on the season temperature in the production area can change. The temperature during day and night shift can be considerably different. The temperature in the lab might be controlled at 23°C, while in the production area the temperature is much higher due to baking ovens or other production machines.
Therefore, it is essential that the glossmeter used is not influenced by temperature changes and the gloss data is independent of the temperature. (Fig. 3)
If gloss values are only stable within laboratory conditions, data cannot be compared. Temperature stability is as important as repeatability and reproducibility because you don't know what the temperature conditions are at different production sites.


Figure 1 Short- and long-term repeatable gloss data with BYK-Gardner micro-gloss: ±0.2 GU


Figure 2 Inter-instrument agreement of BYK-Gardner micro-gloss instruments: ±0.5 GU


Figure 3 Temperature stability between 10°C – 40°C – 10°C

2. A glossmeter needs “health check”

Production environment is often rough and dusty which can affect the performance of your glossmeter as optics can accumulate dust on the lenses. Therefore, the “health status” of the used gloss meter is an important factor and needs to be checked. The BYK-Gardner micro-gloss instruments have an “auto-diagnosis” which checks the actual performance of the instrument and gives you instant feedback:

  • Auto-diagnosis is OK
  • Please clean standard
  • Optics need cleaning -> Send in for service / recertification

The auto-diagnosis is your insurance for reliable measurement data.

3. High gloss, semi gloss, matt - what geometry is best?

The answer is easy: micro-TRI-gloss. The universal glossmeter to measure high, medium and low gloss finishes accurately. Three different illumination angles (Fig. 4) are required to achieve good differentiation of the entire range from high to low gloss surfaces:

- 20° high-gloss surfaces - 60° semi-gloss surfaces - 85° low gloss surfaces

The 60° illumination is used as a general geometry for a wide range of applications with gloss values between 10 and 70 gloss units. If gloss data is higher than 70 GU or lower than 10 GU, this measurement geometry is no longer effective in showing differences as shown by the flat portion of the curve. Thus, the 60° geometry would show little or no difference in this range, while visually there is a clear difference. (Fig. 5)



Figure 4 Standardized geometric conditions


Figure 5 Specular gloss values dependent on measuring angle

4. How many measurements should be taken or the importance of statistics

Here our answer is “ONE reading is like NO reading”.
In order to get a representative value of your product finish a minimum of 3 readings should be taken. And to evaluate the uniformity of your product’s surface finish the average with “ or range (min – max) should be recorded.
The micro-gloss instruments offer a statistic mode (Fig. 6) that can be defined by the user:
A single reading does not give a true picture of the uniformity which is particularly important when evaluating larger surface areas.


Figure 6 micro-gloss display of statistic mode

5. Gloss measurement digitalized

Everyone is talking about digitalization. Why do you still write down gloss values or enter data manually in Excel?

The micro-gloss instruments come with the software smart-chart which allows you to transfer, save and analyze the data in easy-to-interpret trend charts. The saved data can be used for production monitoring with documentation in standardized reports as PDF-file or for transfer to other programs. Always ready for audits and optimization.

6. micro-TRI-gloss – The intelligence in gloss measurement

Repeatable +++ Reproducible +++ Temperature Stable +++ Auto-Diagnosis +++ Statistics +++ Gloss measurement digitized +++ High to low gloss finishes +++ UNSURPASSED

Standards and Literature