Is it true that soaking in salt water preserves the color of clothes: the answer is here
There is a popular life hack on the Internet that washing clothes in salt “fixes” the paint and prevents it from leaking out of the clothes.
Housewives use this method to protect clothes from fading during the washing process.
Salt is used as a mordant for some dyes, so it can help slow the fading of some colors.
However, part of the problem with fabric fading is the chlorine found in most tap water.
Therefore, simply soaking in salt water will not help prevent this process. Sunlight also contributes to fading.
If you dry your clothes in the open air, they will fade faster than if you dry them out of the sun.
That said, adding a large handful of salt to your wash water can help slow the fading of dark colors on natural fibers.
It is unlikely that this salt method will have a significant effect on synthetic fabrics.
