reactivity and mobility of MX dyes
Message: Hi Paula,
Thanks for your very informative website. I am looking for info on color properties... mainly migration, how it blends with other colors. I noticed you have a couple references about fuschia. My own experience tells me that reds and that end of the spectrum migrate less, blues migrate well. I've just never seen this info written down. Do you know of information of this nature?
Actually, the properties of each dye have nothing to do with its color, so we cannot make any sweeping generalization about how reds do one thing or blues do another. One red will do one thing, while another red will do quite another.
Fuchsia, or red MX-8B, is the most reactive of all of the dichlorotriazine (MX type) dyes in common use. This means that, if the fabric is pre-treated with soda ash, or if the soda ash is mixed with the dye, red MX-8B strikes the fabric quickly, and does not spread much at all. Fuchsia's high reactivity also means that this is the fastest of all of the MX dyes to spoil, if you keep it for a week or more. (Note that fuchsia actually migrates rather quickly if the soda ash is not added until after the dye has had a chance to spread on the fabric, as in low water immersion.)
The very similar-in-color red MX-5B is much less reactive than fuchsia, and therefore tends to blend more smoothly with the other colors in direct application. It is also less difficult to manufacture correctly, judging from the fact that all of the complaints that I have seen about bad dye have referred only to red MX-8B and mixtures prepared with it.
Turquoise (turquoise MX-G or Color Index reactive blue #140) is the largest and least reactive of the MX dyes. This means that when people attempt to dye in a cold room, the turquoise will tend to react that least, and be paler than the other colors.
The rest of the MX dyes fall somewhere in between red MX-8B and turquoise MX-G in their reactivity. Other blues will react faster than turquoise and thus appear to migrate less well; other reds will react more slowly than fuchsia and thus appear to migrate better.
To observe the different properties of the individual dyes, you must use unmixed dyes. There's a list of unmixed Procion MX type dyes on my web site at http://www.pburch.net/dyeing/FAQ/pureMXcolors.shtml. It is a great pity, in my opinion, that so many dyers restrict themselves to just mixing fuchsia, turquoise, and yellow, or else rely on mixtures prepared by the manufacturers or retailers, instead of getting to know the different dyes. A mixture of blueviolet (blue MX-7RX) plus grape (violet MX-2R, commonly sold under the nonsensical misnomer of violet MX-G), in low water immersion, gives entirely different results than combining similar colors that have been mixed from turquoise and fuchsia. It is good to have more options, as provided by more individual pure unmixed dye colors.
You can see the results of a couple of my experiments on dye mobility at http://www.pburch.net/dyeing/notebook/notebook1.shtml. This shows only the mobility of the dyes in the absence of soda ash, so that the speed of reaction is not involved at all. The experiment needs to be repeated in the presence of various strengths of soda ash, to show how the two factors, dye mobility and reactivity, interfere with each other. Unfortunately I am not able to do such experiments now myself. It is interesting to note that turquoise, which seems to spread so well in tie-dyeing, actually has quite poor mobility compared to other blue dyes; it is the low reactivity of turquoise that makes it appear to have high mobility in the presence of soda ash, as in tie-dyeing.
Posted: Friday - November 19, 2004 at 11:21 AM