Name: Albert

Country: India
Message: My company uses a lot of fabric that has been dyed or printed with natural dyes. What special care handling instructions do these fabrics require. We get a lot of complaints due to perspiration marks on naturally dyed garments. Is there a reason for this? Do look forward to your feedback !
Many Thanks...
Albert

Do you have any idea which natural dyes, specifically, were used to dye or print your fabrics? It makes a huge difference. It's impossible to say anything about one natural dye that will be true for all other natural dyes. Many natural dyes are mordant dyes, some are direct dyes, and one or two fall into the category of vat dyes.

Another problem is that I strongly suspect that, in many cases, a fabric will be sold with false claims that only natural dyes were used on it. The fabrics may actually have been dyed with a synthetic dye belonging to any of several classes, in particular vat dyes, which are used the same way as natural indigo. This has no bearing on how well the dyes will resist perspiration, but, as you see, it does complicate the question of which dyes were used.

There are two main problems with perspiration. One is the fact that it can be either slightly acidic or slightly alkaline, and it contains salts, as well as an amino acid, histidine, which causes dyes to be more susceptible to light-fading, if it is not washed out before sun exposure. Some dyes will react to the perspiration as a pH indicator, changing color based on the pH. Other dyes will fade in the light, but fade considerably more in the presence of perspiration. The other main problem in perspiration staining, completely unrelated, is caused by the presence of aluminum compounds in the antiperspirants people commonly wear, rather than by the perspiration itself. In some instances, aluminum salts act like a mordant to interact with dyes to change them to surprisingly different colors.

Some dyes, whether natural or synthetic, are very susceptible to the effects of perspiration, while others are resistant. (There is information listed for perspiration fastness for many synthetic dyes in the charts on my page about lightfastness, showing that some synthetic dyes are excellent in this regard, while others are very poor, but unfortunately there is no information there on perspiration fastness of natural dyes.) The best answer to problems with a susceptible dye is to switch to a different dye that lacks the susceptibility. Do you have any alternatives, in the form of different dyes, for the same colors of fabric? The suppliers of your fabrics should be testing their dyes, as used on their fabrics, for perspiration fastness, and providing you with the test results.

Another option is to use a cationic dye fixative that increases resistance to perspiration. Dharma Dye Fixative, for example, which is a brand name for Clariant's Cassofix FRN300, is claimed to increase resistance to perspiration. It will also increase resistance to fading in the wash, though it will possibly, like other cationic dye fixatives, increase fading due to sunlight. A 1990 book by Ernest W. Flick, "Textile finishing chemicals: an industrial guide", lists a number of cationic dye fixatives, including at least one that is formaldehyde-free, that are described as increasing perspiration fastness. One caveat is that many cationic dye fixatives will decrease lightfastness, so you'll want to test whether or not this is a problem.

I'm afraid that I do not have care instructions for unidentified natural dyes. As a general rule, washing separately from other colors in cool water is appropriate for clothing colored with dyes of relatively low washfastness. Perspiration stains will be lessened if the clothing is washed promptly after wear. Some advisors suggest soaking the clothing in a vinegar solution to remove perspiration stains, or an ammonia solution, but whether either of these is appropriate for a particular garment will depend on the specific dyes used; you will need to test to make sure that it does not strip out the dye, before including this advice in your care instructions. 

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