Name: Sylvia

Country or region: USA

Message: Tried searching for answer on your site but was unsuccessful. Am keeping bottles of fiber reactive dyes in a cool, dry location.  Some I've had for about 7 years.  How long is the shelf life of the Procion MX dyes?  Thank you.

Procion MX dye powders, like other fiber reactive dyes, will eventually go bad on the shelf, as they react with tiny amounts of moisture. They will last longer if tightly sealed in jars than if kept in plastic bags, but in any case will eventually go bad eventually, if you keep them long enough.

As you know, they will also go bad much more quickly in a warm place; while I've had Procion dyes that lasted for years in an 80°F laundry room, a single day inside a hot car in the sun with the windows rolled up is enough to cause entire jars of Procion MX dye to completely go bad.

How long it takes for the Procion MX type dyes to go bad is highly variable, and it depends on how much time has elapsed between the manufacture of the dye and the time at which you purchased it, as well as, presumably, on how well the dye powder was purified from moisture, and how well the additional ingredients were added to maintain a balanced pH during storage. All of these factors are impossible for you to determine, but you can easily do an experiment to test how fresh your dyes are.

The big dye retailers suggest that their Procion MX dye powders will stay good for one to two years after purchase. However, dyes found in a less-well-run crafts store might, in some cases, be a couple of years old already, before purchase. I have had Procion MX-type dye from a reputable source that expired not much more than a year after purchase, and I have had Procion MX-type dye that continued to work well and produce strong, intense colors for at least eight or nine years. (I imagine that the latter was very fresh when I bought it, while the shorter-lived dyes had probably been sitting for some years in storage, at various stages, with the manufacturers, some middlemen, or the retailers.) There is no guarantee that the dye will last longer than a year or two after you buy it, but it certainly might; it is worth testing them to see whether they are still reactive enough to be useful.

It's very important to test your older dyes before using them on a large or important project. Do a small tie-dyeing project as a test, or, if you're in more of a hurry, soak a small cotton rag in soda ash, just as for tie-dyeing, then place it in a sturdy freezer-type zip-fastener plastic bag. (The 'freezer' type is sturdier than the 'storage' type of zip-top bag.) Mix up a tiny bit of the dye powder in water (using softened water if your water is very hard) and apply it to the pre-soaked rag. You can do a number of different colors of these test swatches at once in separate bags. Let them rest for fifteen minutes so the dye can soak partially into the fabric, then seal the bags (pressing out much of the air first), place them in a supportive dish, and microwave them for a minute or two, watching closing the entire time. You want the bags to become inflated with steam, but you do not want them to get hot enough to explode and make a mess. Touch the outside of the bags carefully (so you don't burn yourself) to make sure that the fabric swatches are hot, then allow them to cool to room temperature. Rinse them out, as usual, using cool water until the bulk of the loose dye has come out, and then very hot or even boiling water to remove the excess unattached dye. The added heat greatly increases the reaction rate of the Procion dye, so this makes a fast and effective test.

Not all of the dye in stored powder hydrolyzes (going bad by reacting with water molecules) at once. A reactive dye will become gradually weaker with time. A dye which is half hydrolyzed can still work quite well in tie-dyeing, if you use twice as much of it; the only problem is that you then have a huge excess of unattached excess dye at the end, which makes the first washing step, which uses cool water, even more important than usual. If your first rinsing of partially hydrolyzed dye is done with hot water, it will encourage the non-reactive already-hydrolyzed dye to become loosely attached to the fiber, in exactly the same way that poorly washfast all-purpose dyes attach. This means that you end up having to do far more of the hot-water washing to remove the unattached excess dye. It's not as critical to start with the cool water rinse if you have very fresh dye.

Please remember that you do not have to throw away your "spoiled" fiber reactive dyes. They will never again be suitable as reactive dyes, for dyeing anything using the soda ash recipe, but they can still be used as acid dyes, indefinitely. Any recipe that calls for dyeing silk, wool, or nylon, or any animal fiber, using an acid such as vinegar in place of the soda ash, will work perfectly fine with hydrolyzed Procion MX dyes. (For more information on using Procion MX dyes with vinegar on silk, see "Fiber reactive dyes on protein fibers".) If you do not yourself like to dye silk or other animal fibers with fiber reactive dyes such as Procion MX, perhaps you know someone who does, and who will be happy to take it off your hands.

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