Name: Anne
Message: I have been dyeing fabric for 10 years, primarily with Pro MX dyes. I know that Pro MX dyes have a relatively low impact on the environment but I wonder if you are aware of a reliable way to reduce the amount water needed to wash out the unfixed dyes at the end of the dye process.

Also, is there another dye that you feel is more environmentally friendly that gives similar results on cellulose fibers?

Thnaks so much for the information you have made available through your website.

The amount of water required for the washout of excess Procion MX dye is its biggest drawback. 

Some people use a chemical dye fixative, such as Retayne, instead of washing out the excess dye properly, but I really do not like to do this, for several reasons. One is that the covalent bond between reactive dye and fiber is very permanent; the use of the cationic dye fixative sort of 'glues' the excess unattached dye to the fiber, but in a less permanent fashion. A second reason not to substitute a cationic dye fixative for proper washout is that it may reduce the lightfastness of the dye. Thirdly, the cationic dye fixatives should not be washed in hot water, which will tend to remove them, but properly fixed reactive dye is safe at any water temperature, even boiling.

To reduce the amount of time, effort, and water required for washing out Procion MX dyes, first be sure to use PFD (prepared-for-dyeing) fabric or clothing, because it lacks sizings and starches which can interfere with washout; starch in particular will itself accept the dye, and then wash out only very gradually, giving the impression of nonwashfastness. If your water is at all hard, be sure to use a phosphate-containing water softener in the water for mixing dyes, Metaphos or sodium hexametaphosphate, to prevent unwanted minerals from forming hard-to-wash-out dye complexes. These two issues, starch and water hardness, are not the cause of Procion MX's need for a lot of washing out, but they can cause problems that make it much worse.

The real key to reducing water usage in reactive dye washoff is water temperature. Hot water reduces the substantivity of unreacted or hydrolyzed dye. You should always first rinse your dyed items once in cool water, to remove salts and auxiliary chemicals (I like to do this in the washing machine), but after that you should use hot water. If your water temperature is too low, this will reduce the efficiency of washout and make it take longer. Water temperatures of 140°F or above are highly preferable. My "energy-saving" washing machine adds cool water when it is set on hot, so it is necessary to turn off the cool water faucet when filling the machine with hot water. If you happen to have a washing machine with its own heater, as in the case of some front-loading machines, use a higher temperature of water for dye washout, if your fabric/yarn/clothing can tolerate the high temperatures. Boiling water is the most efficient.

It is not efficient to use all this hot water for a single fifteen-minute wash cycle. Instead of letting the water run out after a single cycle, set the machine to presoak to take the greatest possible advantage of the hot water you are using. I'm not sure how much time is optimal; it wouldn't hurt to give the clothing an hour's soak, or longer. Unfortunately, washing machines are not usually insulated, so they do not retain the heat of the water as long as would be ideal. Some dyers use an insulated cooler, such as you might use to keep foods cool, for their hot water soaking step. Hot water poured into a cooler can stay hot for a long time, so this is an excellent way to make the best use of hot water for dye washoff. Soaking overnight in a cooler full of very hot water will reduce the amount of washing needed considerably.

Other fiber reactive dyes are supposed to require less washing to remove excess dye; this is said to be the reason for their being more popular in the tectile industry. The available choices include Cibacron F (Sabracron F) dye, Drimarene K, and Remazol (vinyl sulfone) dyes. I've been using a lot of Remazol dyes in the last year or so, and while I like them very much, I haven't found the washing out to be dramatically better; this may be due to my not taking sufficient care to start the washing-out process with a cool rinse. It is even more important, with Remazol dyes as compared to Procion MX dyes, to start with a cool rinse, as Remazol dyes washed in hot water at a high pH can be stripped from the fabric (before the high-pH auxiliary chemicals are removed by rinsing).


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