Lenses with anti-fog technology are becoming increasingly popular. It is promoted as a product selling point by many manufacturers of sunglasses, safety glasses, and sports glasses on the market. Every cloud, however, has a silver lining. Excellent anti-fog technology can significantly reduce the likelihood of fogging, while a bad frame design and durability can have a considerable negative influence on the brand image. Today, I will share the standard anti-fog testing as well as commercial anti-fog testing methodologies that go above and beyond customer expectations.
I don't know if you have seen the following test video: the operator places the lens on top of a cup of hot water, the steam fogged the lens, and then we can know the anti-fog performance of the lens. However, from the testing point of view, this test method must raise the water temperature to 80-100 degrees Celsius to produce the most obvious fogging effect, thus ignoring the temperature control and fog uniformity, which is far from the standard requirement. I remember a friend in the industry once shared with me an anecdote about how he tested competitor’s lenses when the water temperature was at its peak, and then tested his own lenses when the water temperature was slightly lowered, and the results speak for themselves.
According to ISO 18526-3: Physical and Mechanical Properties, published by ISO in 2020, the anti-fog test requires a sealed design with a laser inspection system to test the anti-fog performance of the lens. This design can reduce the influence of environmental factors (such as temperature, air flow direction, etc.) and analyze the anti-fog performance of the lens by observing the percentage change of relative transmittance.
If this article ends here, I believe that everyone will only be able to comprehend the basic anti-fog lens testing methodologies. Let's think about the reasons why, excluding the wrong test methods, more than 70% of anti-fog products on the market still fail to meet customer expectations. It is because most of the manufacturers stopped at the standard method. Respond to the leading research on anti-fog technology outside the eyewear industry, where the basic test method reflects only one of three droplet morphological changes: diffusion. In practice, two or at most three morphological changes (e.g., tilting technology, bonding strength over time, etc.) are required to achieve optimal anti-fog performance.
According to our team's daily technical work, we have observed that as long as the right anti-fog technology is selected, the relative transmittance of the lenses can be maintained for at least a few minutes or even half an hour in standard tests. But can this result represent the anti-fogging performance of eyewear products? And does it reflect the real experience of users? As mentioned in the standard, there is no accepted test for the resistance to fogging of assembled protectors under all conditions of use.
It is certain that the leading brands of anti-fog eyewear in the market not only adopt excellent anti-fog technology, but also pay special attention to the frame design during the development stage (e.g. adding venting holes to balance the temperature difference between the inside and outside of the frame). At the same time, they will also pay more attention to the anti-fog performance of their products under different environments, as it involves instrumentation technology, if you are interested, please feel free to contact us for more in-depth communication.
Sunbond Optix has applied this brand-new testing concept with our Italian partners, and cooperated with the world's leading sports brand to develop the world's only anti-fog tester that can simultaneously test with international standards and commercial standards, and simulates normal conditions in an "As-worn" state.
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