Name: blue
Message: Hi Paula,
 I dye wool with mx reactive dye (soaking vinegar and applying dye), in this case could you explain to me what "exhaust" the dye means?  Am I to understand the dye that has been mixed with vinegar becomes exhausted and then has little impact on the environment when I dump it out?  What about the dye that is not mixed with vinegar but applied to wool that is vinegar soaked, I mean the squeeze bottle of dye, will time exhaust that so I can feel comfortable dumping it out?
Hope that makes sense.  Totally understand if you can't reply.

It is safe to dispose of Procion MX dyes down the drain. In home-use quantities, it has little or no impact on the environment.

When dye "exhausts", that means only that it has mostly left the dyebath and become loosely associated with the fiber that you are dyeing. The next step is the formation of a chemical bond, which in the case of acid dyes is most likely a hydrogen bond.

Dyeing wool is a fairly neat process, because in many cases all of the dye leaves the solution and exhausts onto the fabric, resulting in essentially colorless water. Dyeing cotton is a very different experience, because there is always a lot of dye remaining in the water after dyeing. However, for individual dyers or small studios, the quantities used are not a problem.

Disposing of household-use quantities of reactive dyes in the public sewer or a septic system is legal and is unlikely to have any impact on the environment; it's a very different situation from the vast quantities of effluant produced by a textile mill. The dyes we use are not particularly toxic. Disposing of Procion MX dyes will not damage your septic system. Procion MX dyes are either metal-free, or, in the case of some colors, contain up to 2% to 5% of a metal ion such as copper (not chromium). In the quantities that you are likely to be using, unless you have a large business, this is insignificant. If you have a septic system, it is sometimes recommended that you neutralize strongly acid solutions with baking soda, or strongly basic solutions with vinegar, before pouring them down the drain, because extremes of pH can be bad for the bacteria that are needed for the proper functioning of a septic tank. However, the dilution of the dyebath by other water that you put down the drain, in the course of a normal day, will probably be sufficient to bring the pH to an adequately neutral level. 

Even if you use a chromium-containing premetalized acid dye, such as Lanaset Jet Black, the overall concentration of the chromium in the dyebath is low enough to present no problem for disposal. (As I calculated on an earlier occasion, a dye painting solution of 1 teaspoon of Jet Black Lanaset dye that contains 2.5 grams of dye, dissolved in one cup (250 ml) of water, contains 0.08 grams of chromium; after being diluted with 50 gallons of uncontaminated water, this dye concentration would meet the US EPA standard for chromium content of drinking water in the US, which is 100 micrograms per liter.) If you set up a small factory to use large quantities of dye, the situation will be different. In that case, you will have to find out the local regulations for dye disposal, but this is not an issue for a single dye artist.

Some mordants are extremely toxic. For example, while the chromium contained in a metal complex dye like Lanaset Jet Black is in the relatively safe trivalent form, the chromium in potassium dichromate solution, or that used with another class of wool dyes called chrome dyes, is the much more hazardous hexavalent form of chromium, listed by the EPA as a human carcinogen. I would not advise the use of chromium mordant solutions at home or in an art studio. They are quite different from working with safer dyes.

More information about disposing of Procion Dyes:
http://www.dharmatrading.com/info/procion_general_info.html
http://www.prochemical.com/StudioSafety.htm

Some other kinds of dyes should not be disposed of down the sink. For example, Pebeo Soie silk dye should be disposed of the same way as unused housepaint, which should not be put down the drain or put in the regular trash. Check the "Waste Disposal" section of the MSDS for the specific dye you are using. Your dye supplier will give you an MSDS for your dye if you request it.

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