Color Fastness to Light: Analysis of 5 Testing Methods in ISO 105-B02

ISO 105-B02 is a testing method for determining color fastness to artificial light, which uses Xenon arc lamp as light sources to simulate the exposure of fabrics to sunlight. It not only provides five testing methods but also includes five appendices, which are quite complex in content. Therefore, operators often encounter many problems in actual applications.

Test Principle of color fastness to light

A specimen of the textile to be tested is exposed to artificial light under controlled conditions, together with a set of reference materials. The color fastness is assessed by comparing the change in color of the test specimen with that of the reference materials used.

Reference Materials and Apparatus

Reference Materials

ISO 105-B02 mentioned two sets of blue wool reference totally, of which the blue wool reference 1~8 is preferred in Europe and the blue wool reference L2~L9 in America. It is noteworthy that the results from these two sets of references are not interchangeable.

Apparatus—Xenon Arc Tester

• Light source: Xenon lamp is used as light source, which provide optimal spectral power distribution across the lamp’s entire 1500 hours service life.
• Temperature: One of two types of black-coated temperature sensor, either a black-standard thermometer (BST) or a black-panel thermometer (BPT), is used to simulate the maximum temperature that the sample surface can reach. And the thermometer shall be mounted in the same plane and orientation as the test specimen.
• Humidity: The presence of moisture can have a significant effect in accelerated laboratory exposure tests. The apparatus shall have the means for providing and controlling moisture to specimens by humidification of the chamber air.
• Covers: Covers shall be made from thin opaque material, for example, high-grade steel, thin sheet Al or cardboard covered with Al foil, for partial covering of samples and references.
• Color matching lamps: in accordance with CIE Publication No. 51.
• Assessment cabinet: complying with ISO 105-A01.
• Sample mounting card: free of optical or fluorescent brightening agent.
• Assessment mask: complying with ISO 105-A01. In order to obtain reliable test results using ISO 105-A02, the test specimen(s) shall be masked with a material that is identical in color to the sleeve that is used to mask the grey scale (5.2.9).
• Grey scale: for assessing change in color, complying with ISO 105-A02.

Comparison of Five Test Methods in ISO 105-B02

The five testing methods provided by ISO 105-B02 have a lot of content and are quite similar, making them difficult to understand. The following table lists the core content of these five testing methods for easy differentiation and comparison.

Items	Method 1	Method 2	Method 3	Method 4	Method 5
Exposer cycle control model	The fading degree of the specimen	The fading degree of the bule reference	The fading degree of the bule reference	The fading degree of the reference specimen	Through measuring the irradiation energy
Reference material	Blue wool reference 1~8 or L2~L9	Blue wool reference 1~8 or L2~L9	Only two pieces of target blue wool reference are allowed	Not blue wool reference, but reference specimens	Expose the specimen separately or together with blue wool reference
Covers	2 covers, a 1/2 cover and a 2/3 cover	3 covers, a 1/4 cover, a 1/2 cover and a 3/4 cover	2 covers, a 1/2 cover and a 2/3 cover	2 covers, a 1/2 cover and a 2/3 cover	Can be covered or not
Test result	Use the level of 1~8 or L2~L9 blue wool reference to represent the level of color fastness to light of the specimen	Use the level of 1~8 or L2~L9 blue wool reference to represent the level of color fastness to light of the specimen	“Qualified” or “Unqualified”, and indicate the reference type of blue wool reference	“Qualified” or “Unqualified”, and indicate the reference type of blue wool reference	Use the level of blue wool reference to represent the level of color fastness to light, or access the level by comparing the Gray scale

How to Select the Test Method

Method 1: Control the exposure period by checking the blue wool reference, each sample shall be equipped with a set of blue wool reference. It is considered the most accurate, serves as a benchmark for other methods, and should be adopted in cases of rating disputes. Applicable to product quality appraisal, contract disputes, quality dispute arbitration, etc. The disadvantage is that the experimental cost is high, the process is cumbersome, and the exposure period is difficult to control.

Method 2: Control the exposure period by inspection of the blue wool references, a batch of different samples only needs one set of blue wool reference, which can save the blue wool reference. Four exposure stages (including initial evaluation) can distinguish and accurately determine samples with different levels of light fastness. Method 2 is suitable for simultaneous measurement of samples of different qualities, with a wide range of applications and large capacity. The disadvantage is that the exposure cycle is too long, with a complete cycle lasting over 300 hours, increased experimental costs and cumbersome process.

Method 3: Used to check whether the sample complies with a known performance specification. The sample only needs to be equipped with two pcs of blue wool reference according to the requirements, and the exposure cycle is also controlled by the fading of the blue wool references. It is economical, simple, and requires minimal use of blue wools. The exposure period can be long or short, making it suitable for verifying whether the product meets a certain specified indicator. However, due to the use of only two blue wool references, only one range value can be given for certain samples, such as greater or less than a certain level.

Method 4: This method is used to check whether one or more samples conformity with an agreed-upon specimen reference. The basic feature is the control of the exposure period by inspection of the agreed-upon specimen reference. The characteristics and scope of application of Method 4 are basically the same as Method 3, except that blue wool references are not used.

Method 5: It is suitable to check conformity to agreed-upon radiant energy levels. The characteristics and scope of application of Method 5 are basically the same as Method 3. The prominent feature is that the exposure period is controlled by measuring the irradiation energy, which is a more scientific method and has good experimental reproducibility.

Bibliography

[1] ISO 105-B02, Textiles — Tests for colour fastness — Part B02: Colour fastness to artificial light: Xenon arc fading lamp test

[2] ORDNUR Textile & Finance, Color Fastness to Light Test Methods and 3 Ways to Improve