Dyed materials exposed to sunlight during the use of the textile product fade or change color over time during all manufacturing stages or during use.
The resistance of the color on the textile material to light is called light fastness. The light fastness test is applied with devices that give the fading effect of the sun. Color fading is mainly a photochemical event. The light energy, which is effective in fading, creates different effects when it falls on an object and is absorbed by the object. When these effects turn into heat energy, they are reflected by the object or appear as a chemical reaction within the object. In order for a light to carry out a chemical reaction in the object, the energy of that light must be equal to the activation energy of the electrons in the molecule of the product. In order for the textile material not to fade, the light energy absorbed by the material should be lower than the activation energy. ( TS 1008 EN ISO 105-B02 )
Used materials
Xenon arc lamp and assembly
opaque cardboard
Temperature sensor (thermometer)
gray scale
Blue Wool References (Reference 1-8 or reference L2-L9 sets)
Sample preparation
Test samples are prepared in such a way that the dimensions are 45 mm x 10 mm.
METHOD 1
This method is used in cases of disagreement in fastness values and only one sample is tested at a time, separate references are used for each sample.
The test sample and references are placed as in the figure.
The middle parts of the samples and references are closed with the XX' opaque cap, as shown in the figure.
The sample and references are exposed to xenon arc light. with the part exposed to light The contrast difference between the unexposed parts continues until the gray scale is 4.
Then, the other third of the samples and references are covered with the YY' opal cap and exposed to light.
No exposure to light with part fully exposed to light The contrast difference between the remaining parts continues until the gray scale becomes 3.
If the contrast is 7 on the gray scale in reference 7 or L4, the experiment is stopped at this stage.
If the color fastness of the test sample is equal to or greater than reference 7 or L7, a very long time is needed to obtain a contrast difference equal to gray scale 3.
If the color fastness is higher, ie reference 8 or L9, it becomes impossible to obtain gray scale 3 contrast.
METHOD 2
This method is used when looking at the light fastness of a large number of samples. Therefore, a single reference set is sufficient as all samples will be processed at the same time.
The test sample and references are placed as above.
The quarters of the samples and references as above are covered with XX' cardboard and exposed to xenon arc light.
Color fastness is evaluated by comparing the color change in the test pieces with the changes in reference 3 and 2 or L4, when the light exposure is a change equal to 5-1,2 with respect to the Reference 3 or L2 gray scale.
The XX' cardboard cover is placed back in the same position and exposed to light until the color change in reference 4 or L3 equals a gray scale 4-5.
At this point, the YY' cardboard cover is placed as in figure 2.
It is exposed to light until the color change in reference 6 or L5 equals gray scale 4-5.
Then ZZ' shape the cardboard coverA quarter of the samples and references are placed in such a way that they are closed. The light exposure process is determined by the following situations.
a) Until the color change in Reference 7 or L7 equals 4 on the gray scale, or
b) For white textiles, until the sample with the best fastness equals 4 on the gray scale, or
c) The test continues until the sample with the best fastness equals 3 on the gray scale.
METHOD 3
This method is used to check a performance property.
The test pieces are exposed to light with two blue wool references.
Wool references are selected from the references with the smallest property of the test pieces and the color fastness below.
It is exposed to light until the reference with the smallest feature equals 4 and 3 on the gray scale.
METHOD 4
This method involves exposing the parts to be controlled together with the reference sample determined by an agreement to light.
The experiment continues until the color change of the reference sample becomes gray scale 4 and/or 3.
METHOD 5
If this method is to be used according to the type of light determined by agreement, it includes exposing test samples to light alone or with references to blue wool.
Experiment samples and references are exposed to light until they reach a certain energy with the determined light.
In sample evaluation, light fastness values are measured with a blue scale.
On the blue scale, 1 gives the worst result and 8 gives the best result.
lessontextile 
