For a more elaborate list of available test methods, please see: Test methods requiring the use of a QUV and Test methods requiring the use of a Xenon Arc Tester.

UV Test Applications and Factors to Consider

The ultimate goal is of UV testing is to “compress time” so that we know how a product will react to sunlight as it gets exposed more and more.  To do so, we want to simulate the sun on an accelerated basis; this process is called “Accelerated weathering”.  Just like for any other accelerated aging process, the goal is to have the best simulation possible with the fastest aging rate possible while not inducing reactions that would not occur under normal exposure conditions.

The two prevalent UV aging type of equipment used nowadays are: Xenon arc  and Fluorescent light. Each technique has pros and cons and each of them can also be used with a broad variety of test conditions that can drastically change the test outcome. Xenon arc testing is mainly used to assess color/appearance changes over time as a result of indoor/outdoor exposure to UV light either directly from the sun or through glass (indoor conditions).

There is no fixed algorithm that allows us to predict accurately what is the actual aging rate also called “time compression factor ”.  However, with Xenon arc, reasonable assumptions can be made to at least approximate orders of magnitude. For more information on time compression factor and the test parameters required see:

• WOM vs outdoor
• ASTM G-155

Fluorescent light accelerated weathering testing is mainly used to assess mechanical properties retention through exposure. This technique is used for comparison/certification purposes. However, scientific literature is clear that this technique, despite its uses, is a poor time predictor. For more information on this test method please see: ASTM G-154.

Micom also offers UVc exposure for surfaces used in healthcare environments.  UVc exposure is often used as a sanitation process in healthcare environments.

Measuring the Results of UV Test Procedures Using Optical Comparisons

What is of interest to most of our customers requiring UV testing is not so much how the exposed samples look upon test completion as much as how different from the unexposed sample they look.

Typically gloss and color measurements a taken at different exposure intervals until the total planned exposure duration is completed.  In some cases, even if the color and gloss are the same we can see significant discrepancies between samples exposed at different time intervals.  This can be explained by the fact that the human eye sees more than gloss and color.

There are three types of reflections; specular, scattered, diffused.  A good example of a high specular reflection object would be a mirror or a perfectly polished metal.  Scattered reflection:  most materials fall into that category; most of the light is reflected in the specular angle but surface defects will scatter the light creating a bell curve deflection. The bell curve shape will depend on the micro-topography of the surface.  A good example of diffuse reflection would be white paper.

Learn more about our UV test procedures using optical comparisons by downloading our brochure

The Human Eye Sees More Than Gloss and Color

Standard Gloss meters (ASTM D523) measures the « shininess » / Brightness (quantity of the light directly reflected from the surface).  However, in comparing gloss measurements with what our eye sees, it is important to be aware that the human eye evaluates much more than the shininess of the surface.  Simply put; two products with a similar gloss can look very different.

This is explained by the fact that whereas a gloss meter can only measure the specular reflection at a specific angle, the eye can see the light scattering as well i.e. a diffuse reflection.Nowadays, equipment with light sensor arrays can take measurements that mimic the light reflection on the human eyes cones.  These new sensors allow us to measure additional parameters: