Selection Guide for Light Fastness Tester

 


What is color fastness to light?

As we all know, textiles are usually exposed to light during their use life, and light has the potential to destroy the dye, resulting in the effect of “fading,” which causes colored textiles to change color, usually light or dark. We call the degree of resistance to the fading effect of light as color fastness to light. The color fastness to light is a very important index in physical testing of textiles. And light fastness tester is the machine for the test.

How to test the color fastness to light?

The test method of color fastness to light is exposing a set of reference samples along with the specimens at the same time and under the same conditions; the color fastness to light is assessed by comparing the change in color of the test specimen with that of the reference materials used.
Color fastness to light can also be divided into: sunlight (which can be exposed to several different colors of sunlight) and artificial light (xenon arc or carbon arc). In order to control the test conditions in the laboratory and speed up the testing process, the labs generally use artificial light source, so they need a color fastness tester which can simulate and strengthen the natural environmental factors such as the light irradiance, humidity, temperature, light and dark cycle and spray etc.
At present, ISO 105 B02 and AATCC 16 are the two commonly used standards to test the textiles’ color fastness to light internationally. Below the writer give the key control parameters of two test methods.

Types of light fastness tester

There are three kinds tester for textile color fastness to light if dividing by light source: The tester with xenon arc lamp as light source, the tester with carbon arc lamp as light source and the tester with mercury lamp as light source.

Xenon arc lamp tester

Xenon lamp has been used as an artificial light source for the color fastness test for a long time, because the spectral power distribution curve of xenon arc lamp is close to sunlight, and at the same time, the ultraviolet, visible and infrared wavelength generated by xenon arc lamp are the closest to sunlight at present.
The xenon arc tester also have two types according to different cooling method for xenon arc lamp, air cooled and water cooled models.

Carbon arc lamp tester

Carbon arc lamp is the earliest light source for color fastness to light test in textile industry. Carbon arc lamp is divided into two kinds, one is closed carbon arc lamp, the other is solar carbon arc lamp. Both of these carbon arc lamps are used in early equipment, the former is initially used for textile light resistance test, the latter is initially used for coating light resistance test. The luminescent body of the enclosed carbon arc lamp is a group of carbon rods. However, the spectral energy distribution (SPD) of the arc light emitted by carbon rods is quite different from natural sunlight. There is neither short wave ultraviolet radiation nor high intensity energy of sunlight between 400-800nm in natural sunlight. The SPD matching between solar carbon arc lamp and natural sunlight is improved, but the spectral distribution between the two is still different between 50nm and 350nm. Therefore, in general, the correlation between the carbon arc lamp test results and the actual weather resistance of the product is poor. So the carbon arc lamp has is not so popular compared with xenon arc lamp tester.

Mercury lamp tester

Mercury lamp’s spectral lines are mainly in the ultraviolet part, the wavelength concentrate around 365mm. It is mainly used for outdoor products durability test.
The more information about how to choose light fastness tester can be found here.

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