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Wet&Dry Cleaners’ Guide — Color fastness

Color fastness

by Roberta Binotto

Whenever textiles are laundered at home or professionally, we expect their color to be unaffected by the water, organic solvents, detergent, temperature, or mechanical agitation involved in the process. We also do not expect color to bleed out and stain other articles in the same load.

In general, color resistance to the action of external agents (water, sweat, washing, rubbing, light, etc.) is defined as “COLOR FASTNESS”, and evaluated based on two factors:

  1. fading, meaning the change in color resulting from external agents
  2. bleeding, meaning the amount of color transferred to adjacent fibers.

Color fastness is numerically quantified using two GRAY SCALES, one for fading (fig.1)

1 immagine PICCOLA GUIDA OK sala 11 giugno  RIVEDUTA 1 e _3_-001

and the other for bleeding (fig.2):

 2 immagine PICCOLA GUIDA OK sala 11 giugno  RIVEDUTA 1 e _3_-002

These chromatic scales are based on a unit of measure called “index” which ranges from 5 (= best result, no fading or bleeding) to 1 (worst result, maximum fading or bleeding).

The color fastness of different textiles can be analytically identified in the lab though standard color resistance tests. Most of all, it is important to know if the color can withstand these actions:

DRY AND WET RUBBING (UNI EN ISO 105 X12 method)

This simple yet crucial test consists of rubbing the textile first with a piece of white cotton cloth which is dry at first and soaked in water thereafter, to verify how much color is transferred to it.

An intense color stain indicates that the fibers of the article contain an excessive, poorly set amount of dye, which is likely to cause problems.

DRY RAB TRANSFER WET RUB TRANSFER
DRY RAB TRANSFER
WET RUB TRANSFER

An intense color stain indicates that the fibers of the article contain an excessive, poorly set amount of dye, which is likely to cause problems.

SWEAT OR WATER (method UNI EN ISO 105 E04 or E01)

5 imamgine Documento5-001For this test, first the fabric is soaked with artificial sweat or water first, and then subjected to a predetermined amount of pressure using an instrument called “perspirometer”. If the dye did not set properly, color will be transferred from the 4 foto Documento5-001fabric being examined to the reference standard sample. This makes it possible to verify the likelihood of problems arising as a result of the material lying in contact with others of a lighter color when soaked with water or sweat.

WASHING IN WATER (UNI EN ISO 105 C06)

This test simulates the standard washing process using detergent and water at the temperature indicated on the garment care label. It is used to verify how much color the garment releases into the wash water and if any of the color is absorbed by other materials being washed with it (the picture shows a typical example of poor wash performance).

ARTIFICIAL LIGHT (UNI EN ISO 105 B02)

8 imamgineDocumento7-001For this test, the textile is subjected to the action of an artificial light source known as a Xenon lamp, the light spectrum of which is quite similar to natural sunlight although far more intense energy-wise.

The result of this test, unlike all others, is not expressed as a gray scale index. They are based on a blue scale ranging from 1 (worst result) to 8 (best result), which is irradiated together with the test sample.

9 immagDocumento7-001

This type of test can replicate and help prevent defects typical of the “shop window effect”, where the most exposed areas are undesirably affected by the temperature and intensity of the light (fig.3).

10 foto PICCOLA GUIDA OK sala 11 giugno  RIVEDUTA 1 e _3_-001

The conditions mentioned thus far are only a few of those that can be assessed by a lab. Now let’s take a look at a specific case of defective color.

 Lab case study

There are very peculiar cases where the combined action of two different agents, which separately would not affect the color, will cause it to change drastically.

Shown in the pictures below is the subject of the case study, a pair of work trousers which although worn for a short time, exhibit severe color degradation (the images clearly show the extent of the damage, even by comparison with new trousers).

11  a foto PICCOLA GUIDA OK sala 11 giugno  RIVEDUTA 1 e _3_-001

Based on the fact that the most severe damage was localized in areas exposed to sunlight, colour fastness was tested under artificial light. The resulting values were acceptable and certainly not apt to justify damage of that magnitude.

The test was then repeated after soaking the garment with artificial sweat solution, both acidic and alkaline-based. The result can be grasped just by looking at the image below:

1 piccoalg guida 06 INTERNET 2015-001

Although the color fastness of the dry textile may be acceptable, when sweat (especially alkaline) soaks into the material, photo-chemical degradation of the color is triggered and advances at a much faster rate than normal, to the extent shown by the case in question.

2 piccoalg guida 06 INTERNET 2015-001

Detergo Magazine -June 2015

 

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