After receiving a few questions regarding the chemical make up of Procion MX dye, I did some research. Besides finding out the actual chemistry involved, I also found out something that I had been doing that is incorrect. I copied a portion of the information from a website (below in blue) that deals with the chemistry in great detail. The information that is most relevant is regarding premixing. Previously I have premixed dyes in small 8 oz. plastic bottles. This would last for several project so was quite convenient. I haven’t had any problems, although I did have a question from a friend who was having a difficulty with black actually being very dark blue. It is not uncommon for blacks to actually be very dark blue so I felt he may have had some other brand on hand and mixed them up.I suspect the premixed black had possibly reacted with the water he had used, making it turn blue over time.
It seems that Procion MX dyes should NOT be premixed with water. You will note below that the very thing that makes Procion MX very durable for washing (when used in fabric) also makes it not suitable for premixing. The Procion H dyes referred to – unlike the MX dyes – require heating during the dying process. MX does not require heat, part of which makes it so suitable for using on wood.
Moral of the story: when using Procion MX, mix only what is required for the job at hand. A small price to pay for something that brings out the chatoyance in figured grain so well.
Procion MX dyes are described as dichlorotriazine dyes, while Procion H dyes are less reactive monochlorotriazines. Here are the full chemical names and/or structures for several Procion MX dyes. Note the cyclical structure with two chlorine atoms on it: these are the reactive sites that react with -OH groups on the cellulose fiber to create the strong covalent bonds that are responsible for the dichlorotriazines’ extremely high washfastness. Procion H or monochlorotriazine dyes have one, rather than two, of these chlorines, for a similarly strong bond, but higher heat requirements due to their reduced reactivity – which also makes them store well in water, unlike the Procion MX dyes.
As always, I encourage your comments and questions, so please refer to the tag line at the bottom of the article to post a comment.