What do the letters and numbers in the code name for a Procion MX type dye mean?

Here's an example of a code name for a specific dye color:

Procion blue MX-2G

Each dye code name consists of a brand name, then a color name such as blue, followed by a prefix indicating the type of dye (usually "MX" for dichlorotriazine dyes), then a dash, then (optionally) a number, and finally a letter, usually G, R, or B.

G stands for "Gelb" which is German for yellow.
R stands for "Rot" which is German for red.
B stands for "Blau" which is German for blue.

The number before the letter is a sort of indication of strength, i.e., "8B" means more blue than "5B".

So, red MX-8B is a little more blue than red MX-5B. (They are also completely different chemicals with different properties, so it often matters a great deal which one you use, even though their colors are extremely close.)

Blue MX-G is yellower (i.e., a little greener) than Blue MX-R.

Yellow MX-3R is a redder yellow (i.e., more orange) than yellow MX-4G, which itself is not quite so true a yellow as yellow MX-8G. Most dye companies call yellow MX-3R(A) "golden yellow", but another company calls quite a different dye "golden yellow", while calling this one "deep yellow". We like to use the MX codes because they are more generic than the common names. If someone says "golden yellow", you really don't know which dye they are talking about, but if they give you the MX code, you know exactly which one they mean.

Base color names

What complicates this tidy scheme is the fact that the base name was chosen by the original manufacturer, and not always in the most logical fashion. Turquoise MX-G is a completely different molecule than Blue MX-G. Unsurprisingly, from the name, it is a greener color. If complete understandability had been the only naming criterion, it would have been named something like "blue MX-8G", but "turquoise MX-G" must have sounded better to the manufacturer.

Other letters - X, A, N

Blue MX-7RX is, as its name suggests, on the violet side of blue. Why the X? We have no idea what it really means, but it is an identifier for a slightly different formula. We have never seen a Blue MX-7R being sold without the "X", but if we do, we should expect it to be a little stronger or a little weaker or easier to dissolve or less dusty or something. ProChem sells Yellow MX-3RA while Dharma sells Yellow MX-3R. The color is exactly the same, but Yellow MX-3RA is denser than Yellow MX-3R; don't use the exact same amount of it as you would of the other. ("A" is said to stand for "American", as though the recipe were originally devised for an American customer.)

Does every dye company use these codes?

There is no law that says that dye sellers must use these same codes. It just makes it easier for dye manufacturers and dye wholesalers to communicate. How much of a priority clear communication may be varies according to the dye customer. Often you see dichlorotriazine dyes, the type we know as Procion MX type dyes, being sold as "M-type" dyes, as well as "cold brand" dyes. Rarely you see a company that confuses things by not even using the M is a prefix. For example, Standard Dye sells Permabril C dichlorotriazine dyes. Probably some of the "Procion MX" dyes we buy were sold to our retailers as Permabril C dyes. These are not made by the company that owns the Procion MX name—in fact, Dystar, which owns the Procion name, no longer lists any Procion MX dyes for sale at all!—but the dyes are pretty much identical (with a major quality exception for red MX-8B, commonly known as Fuchsia).

Sometimes your supplier's MX codes are wrong

Mistakes have been made. Have you ever seen a reference to "Violet MX-G"? What color could that be - a yellowish violet?! Add yellow to violet and you get brown, not the lovely red-violet this color truly is. The explanation is that Standard Dye is the company that first starting selling this dye to our dye retailers. (I have no clue as to whether or not they are still the suppliers.) Standard had a chemist (maybe they still do) who delighted in slapping utterly incorrect names on dyes. He decided to rename violet MX-2R to the useless meaningless name of "violet MX-G" for his own obscure reasons. It completely screws up the whole system! Stupid, I call it. The lovely reactive violet 14 is properly known as violet MX-2R, but one must also mention the misnomer under which this dye is sold, in order to avoid confusion.

Why we like MX code names

The reason why we like to use the MX codes is because, in spite of imperfections in the application of the naming scheme here and there, at least it tells you something about the color. We can be clearer about which dye we are talking about if we use the Colour Index names. For example, nobody would ever get the wrong idea that blue MX-G is just a more concentrated version of turquoise MX-G if we referred to them as C.I. reactive blue 163 versus C.I. reactive blue 140. It's hard for most people to remember numbers, though, when they are just randomly applied. The C.I. name tells you nothing about how greenish or how reddish a blue dye is; all it tells you is something vague about which dye was first described in the Colour Index.

Sometimes they don't know!

Another issue is that our dye retailers do not always know what the Colour Index names of their dyes are. ProChem never did get back to me to let me know whether their "Boysenberry 802 Violet MX-BR" is really magenta MX-B or C.I. Reactive Violet 13. Maybe their suppliers did not want to let them know! Maybe they've become unaccountably secretive after being otherwise open. I don't know. My best guess is that it is magenta MX-B. That boysenberry color is obviously not bluer than violet MX-2R! The other possibility is that we might be looking at pink MX-B, reactive red 74, which I recall Standard telling me might be introduced by them.

Other dye classes

Other classes of dyes appear to have a naming scheme something like this, but it's hopelessly confused, at least in the case of the acid dyes. For example, a single dye, C.I. Acid Brown 14, has the synonyms as different as the following (among others): Resorcin Brown RN, Coriamine Brown 3R, Resorcine Brown R, Amacid Resorcine Brown 2R, Mitsui Acid Brown 3R, Fenazo Brown N, Dermina Brown G, Aciderm Brown GRF, and Brown 5EMBL. What a mess! There you just have to stick to Colour Index names and numbers.

How to find the MX Codes for the Procion MX Type Dyes You Use

The best place to look to understand your Procion MX dye names is my page on "Which Procion MX colors are pure, and which mixtures?". If you mention a dye color name without either MX code or Colour Index name, you must also make it clear exactly where you bought the dye, as otherwise we have no idea which dye you mean, exactly.

What about manufacturer's mixtures?

Not all Procion MX type dyes that are listed in your retailer's catalog with MX codes are single-hue, unmixed dyes. Some are mixtures of dye colors, mixed by the manufacturer and sold to your dye retailer. These mixtures may be consistent from one retailer to another, if they are sold to them by the same dye manufacturer. (Then again, they might not be quite the same, since they are likely to be from different dyelots.) Other colors which are not labeled with MX codes are typically mixtures prepared in-house by your dye retailer. Dye mixtures with MX codes are listed in the second table, towards the bottom, on my page of Which Procion MX colors are pure, and which mixtures?. The most popular of these manufacturers' dye mixtures include red MX-BRA, blue MX-4RD, red MX-GBA, and black MX-CWNA.

Much of the text on this page was originally published in the Dye Forum on August 21, 2006.

Page created: August 21, 2006
Last updated: August 21, 2006
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