Name: max
Message: Hi,
After reading your page about setting dyes into fabrics, I just wanted to let you know that while entitled 'How to set dyes into fabrics,' you really don't do a good job of explaining that. Other than mentioning some commercial brands, you don't flesh out the info. When can a person use vinegar, and what should a person use for cotton, which you say is NOT acid-dyed?

Perhaps you should go back and read the page on setting dye in purchased clothing again. As it says in the second paragraph, "Vinegar will help set some acid dyes, but only if applied while it is gradually heated to a simmer (generally in the presence of salt), solely in cases in which this necessary part of acid dyeing was omitted." That is when you can use vinegar.

Vinegar is used dyeing during the process of dyeing an animal product such as silk or wool, or nylon (but no other synthetics). You should mix the acid dye with water and either white vinegar or citric acid, and heat it to a simmer with the fiber, after which you should maintain that temperature for at least half an hour. Once the fiber has been removed from the dyebath and the dye has been poured out, it is too late to expect good results from the use of the acid (such as vinegar). Vinegar may or may not be at all helpful if applied later. However, vinegar is excellent for restoring some of the softness that is lost when silk is washed with typical high pH detergents. You can use one cup (250 mls) of white vinegar (5% acetic acid) in the final rinse of any laundry, as a substitute for fabric softener.

What should you use on cotton? If you do not know exactly what type of dye was used, you cannot expect to successfully set dye on cotton, except with a commercial bulking agent such as Retayne, which, due to its mode of action, is effective on many different types of dye. You cannot set an unknown dye on cotton using vinegar orsalt. There is only one case in which a common household chemical may prove of any use, and that is in the case in which someone has attempted to dye cotton with fiber reactive dye, and inadvertently omitted adding the soda ash that is required in the recipe. In that case - if the mistake was yours and you know exactly what you did - you may find that soaking in soda ash solution is effective. However, this is not going to help if your cotton was dyed with direct dye or vat dye or sulfur dye, three types of dyes commonly used on purchased clothing. If you have a problem with cotton that has been dyed with any of these dyes, or if you do not know what kind of dye was used on your cotton, your only hope is to use one of the commercial dye fixatives such as Retayne.

It is almost always better to return the defective garment to the manufacturer and demand properly dyed garments.