Color fastness is a term used in the textile industry to describe the resistance of a fabric against color fading or color transfer.
There are different types of colour fastness. The common ones are:
Color fastness to Washing
Color fastness to Light
Color fastness to Crocking/Rubbing
Color fastness to Perspiration
For bag manufacturing industry, we are usually most concerned with color fastness to Crocking/Rubbing, and this is what we will be focusing on in this article.
What does Crocking mean and why is it important?
Crocking means the transfer of color from one fabric onto another by rubbing. A fabric with poor color fastness would transfer its color easily onto other fabrics, especially to white color fabrics.
No one wants his/her white shirt to get stained by his/her backpack. That is why color fastness to Crocking/Rubbing is especially important in the bag manufacturing industry.
How to determine the color fastness of a fabric?
We can check the color fastness of a fabric by running a test. The test methods that we usually use for Crocking/Rubbing are called "BS EN ISO 105 X12" and "AATCC 8". We need a Crockmeter to carry out this test and below is how it typically looks like.
During the test, a white conditioned rubbing cloth would be rubbing on the test specimen, back and forth in a straight line for 10 cycles with downward force. Usually, two tests would be made, one with a dry rubbing cloth and another with a wet one.
Then, after the test is done, the tested rubbing cloth should be evaluated against the grey scale under decent light source.
The color fastness to Crocking/Rubbing is categorised from 1 to 5. The higher the number, the better the fastness.
Ideally, we want no colour transfer at all. Unfortunately, it is not possible in real life. So, what should be considered acceptable? Below is the standard most companies use:
For Dyed Textiles such as Polyester and Nylon, and Synthetic Leather such as PVC and PU, the common standard is Dry: 4.0 and Wet: 3.0.
For Print Textiles, Denim, Canvas, Velvet Textiles and Genuine or Suede Leather, the common standard is Dry: 3.0 and Wet: 2.0.
What are the Factors that affect color fastness?
Material composition affects a great deal for color fastness. By nature, some materials are always better than others when color fastness is concerned.
For instance, the color fastness of Polyester and Nylon fabrics are normally one grade better than Denim's and Canvas's. Therefore, the common standard for Denim, Canvas, Print Textiles, Velvet Textiles and Genuine or Suede Leather is set at a relatively lower level, which is only Dry: 3.0 and Wet: 2.0, as people in the industry understand and expect that it is difficult for these materials to achieve a high color fastness standard.
As such, during product development, when these fabrics are involved, it is better to pay special attention to make sure that the material suppliers would handle the fabrics carefully. Otherwise, you might end up with a product that will stain clothes.
Color also affects color fastness. Materials in darker colors tends to have lower color fastness than lighter color materials.
Also, due to the chemical properties of the dye, there are a few colors that are now widely known to be more problematic, such as Red, Navy Blue & Black.
Other factors that affect color fastness include the specific dye used in the dyeing process, the dyeing process itself, any additives, fixatives or softeners used, and the way of washing of the fabrics etc.