A bit of Chem: Flavonoids and Anthraquinones

So, someone asked a question while I was away. It was a good question.

It had to do with natural dyes and flavonoids, and how they compare to anthraquinones.

“What?” some of you are no doubt querying.

The Difference Between Dyes

Fiber Chemistry

Anthraquinones are a common structure for acid dyes to be based off. Flavonoids are a common structure for some natural dyes.

So here’s the most basic structure of an anthraquinone:


And here’s the most basic structure of a flavenoid:

You can see, they’re pretty similar. Big difference is that the phenol rings (the hexagons) have a linker in flavenoid, and not in the anthraquinone. As you get more complicated, that starts to seem a little less important.

One important thing to note here is that these basic structures make the chemical colored, that’s actually the most defining feature of a dye chemical. The “dye” aspect is usually added on after the fact, or if it’s a natural dye, is a lucky chance addition for the dyer.

Here are some simple-ish anthraquinone dyes:


Acid Blue, Vat Violet, the dye that makes your gas blue, and Disperse Red

These are dyes made synthetically, but the colors from lichen, fungi, rhubarb, buckthorn, and senna are all anthraquinone colors as well.

Here’s an example of a far more complex flavenoid dye. This is marigold dye, “patulitin.”


And here’s a few flavenoid colors…

Luteolin, the yellow from weld:


Quercitin, the yellow from onions (and part of the color from oak and tea):


Which is all a very long, roundabout way to say that structurally they are very similar. Most of the natural dye flavenoids are in the yellow/orange range (but not universally so), while the anthraquinones are mostly in the blue range (but not universally so). The main difference between them as DYES, is that with most flavenoids you need a mordant in order to serve as a linker to bind it to the fiber, while most anthraquinone dyes are synthesized with an acid moiety like a sulfate or the like. But the natural ones (aforementioned lichen, etc) will need a mordant, just like the flavenoids.

Hope that answers your question!

That’s all for now!
~The Gnome


Dyeing 101: The Chemistry of Fibers – Soy, Milk, Chitin, Etc.

Allo! Another chemistry lesson!

So, a lot of people know that fibers are largely divided into two classes. Protein, and cellulose. Proteins are what make the strong flexible fibers in animals, hair, skin, muscles, even collagen. Cellulose is the main ingredient in plant cell walls. It’s what gives the plant its strength and shape.

Many of the fibers are thus obvious to categorize. Wool and alpaca and dog and bunny and goat are all animal fibers, and all protein fibers. Cotton, flax, hemp, and nettle, are all cellulose, plant fibers. But many fibers are not obvious, like chitin, or seem obvious but actually aren’t, like soy or even silk.

So the first thing to understand is the basic chemistry of a “protein” fiber or a “cellulose” fiber. How are they the same, how are they different?

Protein Fibers:

We’ll start with a protein fiber. Protein fibers are actually made of multiple layers of proteins bound to each other in different ways to make the many different types of fibers you’re familiar with. However, here’s the important part.

Protein molecule

This is a simple, four amino acid (piece) protein. If you stuck a bunch of these together you’d have a “polypeptide,” a protein fiber. You can tell it’s four pieces, or amino acids, because I’ve conveniently labeled each amino acid’s “R group” with a number. That’s because what’s in the R group doesn’t really matter for this part of the discussion. They affect things like durability, crimp, and tensile strength, but not dyeing.

What’s most important for your dyeing purposes are those N-H bits, called “amine” groups (which is how amin-o acids get their name!). These amine groups are the signifying feature of a protein. And, if you remember my previous post on the difference between acid and reactive dyes, they’re the part that acid dyes bind to.

So, any fibre that’s made up of these amino acids, with their NH and NH2 groups, is a protein fiber, and will dye with acid dyes. Got it?

Cellulose Fibers:

Cellulose fibers have a different structure, with no amino groups. Celluose is made of strings of glucose sugar instead of amino acids. Like protein fibers, natural cellulose fibers are more complicated than this, with layers and such, but also similarly, this is the important part.


The important part here is those “OH” groups hanging off the edges, called “hydroxide” groups (’cause they have a HYDRogen and an OXygen). Those are the parts that interact with reactive dyes (when you put the fiber in a basic solution). So, any fiber made with cellulose molecules, is a cellulose fiber, dyed with reactive dyes.

“Odd” Fibers:

So, that’s the easy part. Now lets look at some weirder ones. We’ll start with soy. Soy is a plant, right? Of course! It’s where we get edamame and soy beans and tofu. Mmm tofu. Yay plants! So it should be a cellulose fiber, that dyes with reactive dyes, riiiight?

Well… no. (Bet you didn’t see that coming!)

You see, there’s another way to divide fibers, though it’s not as all-around helpful for things like dyeing. Synthetic and natural. That is, fibers which are used more-or-less “as is” and fibers which we have to create.

The obvious “fibers which are used more-or-less ‘as is'” are the wool/hair/fur/cotton fibers. We pluck or shear them off the animal or plant, clean them, and use them, simple. Slightly less obvious are the “bast” fibers which are cellulose fibers that naturally grow for strength and flexibility in some plants. Flax and hemp are excellent examples of bast fibers. To collect these we “ret” (partially rot, how’d you guess?) the rest of the plant away from the bast fiber, clean it up, and spin it. Examples include of bast fibers are flax/linen, hemp, ramie, some bamboo, nettle, wisteria, and milkweed.

So the “natural” fibers are the fibers which already exist and we just collect and use them.

The “synthetic” fibers are fibers that we have to make. Most people, when they think of “synthetic” think of things like acrylic, plastics. And, of course, acrylic is synthetic. But in this case, I use synthetic in its more complete sense of synthesized, or combined from two or more parts. Again, there are some fairly clear cut examples of this, and more confusing ones.

A clear example is milk, and a confusing one is the soy I mentioned above. We’ll start with milk.

Milk is clearly… not a fiber. And not particular fibrous to boot. If you’re like most non-chemists you probably wonder where in the heck they found fiber in milk! And you’d be right, there IS no fiber in milk! What there is, is casein, a protein made of many amino acids. In fact, it’s the majority of the protein in whey protein you can get as a dietary supplement. Another protein that looks roughly like…

Protein molecule

So you string a bunch of those together, and you get a fiber! And, as you’d expect looking at the chemistry, this is a protein fiber, made with lots of amino (NH and NH2) groups and thus dyes with acid dyes.

Now, back to soy. Soy is, indeed, a plant, but the thing to know about soy fiber is that it is not a bast fiber. That is, the soy fiber doesn’t come out of the stalk of the plant as a fiber. Instead, soy fiber, like milk fiber, is a synthetic fiber, actually made from the bean. The leftovers of the bean after they make other products have a high quantity of the amino acid lysine in them. So, they take the amino acid lysine, stick it all together in strings, and you again get…

Protein molecule

A protein molecule all stuck together into long fibers, and thus a protein fiber that dyes with acid dyes, even though it came from a plant!

The Odd Case of Synthetic Cellulose:

Many of the other “new” fibers are in this synthetic class, but are made slightly differently than soy and milk. Seacell, Viscose, Tencel, Rayon, and Lyocell are all examples of what is called “regenerated cellulose.” These terms can be a bit confusing as they’re all essentially the same fiber with variations in word choice or fiber origin.

Basically, they take an already existing cellulose (wood, seaweed) and then break it down and string it back together into fibers to look like this again.


Bamboo is an interesting example in that it exists in two forms. There is “bamboo rayon” which is a regenerated form of bamboo and far far more common. However, bamboo does also have a bast fiber that can be harvested and used. Both are still cellulose fibers, of course, so will dye with reactive dyes.

“Combination” Fibers:

Finally, two of the odder examples of fibers… silk and chitin. We’ll start with chitin.

Chitin fiber, also called crab fiber, comes from exactly that. The chitin (shell) of crabs. It could also come from the chitin in insect shells or shrimp shells or any other arthropod. So… clearly not a cellulose fiber, right? Since there’s no cellulose in a crab.

So what is “chitin” actually made of? Well, the chemical answer is “polymerized N-acetylglucosamine.” Now, what do you notice about that long, complicated word? The first thing with any complex chemistry word is to split it into it’s pieces.

So… “polymerized” means it’s something all strung together, interesting but not useful. “N” well that’s boring, useful to a biochemist to know where it came from, but not for anyone else. Ok, what else? There’s “acetyl,” “glucos,” and “amine.” Ah, now these could be useful.

Depending on your memory, you’ll have already locked onto the second two words, “glucos” which looks a lot like “glucose” and “amine.” Good job, those are the important parts to us.

But now you’re thinking, “But Gnome, wait, glucose is what you said cellulose is made of! And amines are what you said proteins are made of! What are you trying to pull here?!”

Well… I also told you chitin was weird, didn’t I? Because you’re right, glucose is what cellulose is made of, and amines are what proteins are made of! And “glucosamine” is a glucose with an amine group! Ok… so… lets draw out the chemistry and see if that tells us anything, ok?

Chitin Fiber

Chitin fiber is made of strings of this. You’ll notice overall it looks a lot like the cellulose fiber, and in fact you can actually make half-cellulose half-chitin fibers! But remember how I said what the important parts of the protein and cellulose fibers were in terms of dyeing?

Chitin Important Parts

In pink are the OH, hydroxide, groups that are useful in reactive dyeing. In green are the NH2, amine, groups that are useful in acid dyeing. So you can see that chitin is odd in that it will bind with both acid and reactive dyes. But you can also see that it will bind better with reactive dyes, as there are more hydroxide binding sites. And you can guess that overall it will behave like a regenerated cellulose fiber.

Now, silk. Similarly odd. Silk is an animal fibre, but unlike most animal fibers, it’s not a hair/wool/fur fiber. Instead, silk is formed of protein polymers layered on top of each other. Each repeating motifs of this sequence…

Silk Structure

If you look at it the same way as we looked at the chitin fiber, you can see that there’s a lot of amine (NH and NH2) and only one hydroxide (OH) per stretch of silk. So, in reverse of chitin, silk dyes more easily (and usually more deeply) with acid dyes though reactive dyes will also bind to it.


So, that’s the dyeing chemistry of fiber, with a focus on how they differ and the odd fibers.

Protein fibers are made of amino acids and include: wool, alpaca, dog, goat, rabbit, milk, silk, and soy.

Cellulose fibers are made of strings of glucose and include: cotton, flax/linen, ramie, bamboo, seacell (seaweed), tencel (wood), hemp, wisteria, nettle, and milkweed.

Chitin dyes as if it was a cellulose fiber, even though it’s not cellulose. Silk dyes as the protein fiber you’d expect but will also dye like a cellulose fiber though not well.

So. Any questions?

And, of course, your requisite gratuitous puppy.


~The Gnome

Dyeing 101: Know Your Dyes – What’s the Difference Between an Acid Dye and a Reactive Dye?

I have a weekend update to do, and some fiber to get up, but my brain is in chemistry mode right now, so I’m going to post about that instead.

So, there are a lot of dyes out there in the world, made by a lot of different companies.

The most common kinds you will run into are as follows:

Acid Dyes

Reactive Dyes

Direct Dyes

There are subclasses of most of these, and some crossovers. I’ll also briefly touch on a group called “Disperse Dyes.”

Ok. So, the difference between each of these classes of dye is in the way they interact with the fiber you’re dyeing. That is, they have a different chemistry. No, not scary! Get back here! I’m going to explain things logically and slowly, and if you have questions, feel free to ask them. I’ll try not to overwhelm you with jargon without explanation.

I’m going to go through them from one end of the chemical spectrum to the other, starting with my favorites, acid dyes.

Acid Dyes:

First, what does this group include? Some of the things you’re probably familiar with…

Kool Aid
Most food dyes, especially reds

and some you’re likely less familiar with…

Jacquard Acid Dyes
Prochem Washfast Dyes
Greener Shades Dyes

And more! But they all work via a similar chemical mechanism.

I’ve posted about acid dyes before, but I’ll duplicate some of it here.

First, the “acid” in “acid dyes” refers not to the dyes themselves, but to the environment they bind in. For kool aid, the acid is already present in the mix (in the form of citric acid crystals), for other dyes, it’s added as vinegar (which is acetic acid) or sometimes citric acid.

Safety Sidenote: Both acetic and citric acid are food acids, that is, they’re not terribly toxic and won’t kill you. However, when dealing with concentrated citric acid, or any hot bath with acid in it, be careful. Inhaling large amounts of vinegar steam can irritate your throat and lungs and eyes. Submerging your hands in these acids for any length of time can cause irritation and some skin peeling. Better safe than sorry.

Now, some acid dye chemistry!

Acid dyes work via a combination of interactions with the fiber. I’ll explain each one.

Primary: Ionic bonding
Secondary: van der Waals, Hydrogen bonding

Ionic bonding is a bonding between different charges on two molecules. Imagine acid dyes like little magnets. Remember how if you put two magnets together, you have to put the S and N ends together, or they’re push instead of pull together? Some molecules work the same way.

van der Waals interactions are like mini ionic interactions. Instead of a whole magnetic pole interaction, it’s a tiny fraction of one. But they add up.

Hydrogen bond interactions are weaker than ionic and stronger than van der Waals interactions, but use the same idea but specifically involving hydrogen.

Acid dyes are “anionic” meaning they have one full negative charge, think of it as one “south” magnet end.

Acid dyes can therefor bind to fibers which are “cationic” meaning they have one full positive charge, or one “north” magnet end.

An acid dye binds, like a magnet, when its “south” end binds to a fiber’s “north.”

There are many different ways to build an acid dye to get this “south” magnet effect. Some are strong, and some are weak. Here are a few examples.

You’ll notice that in all of these examples, an SO3 group (or two) is present. This is the “south pole” for these dyes. The rings are what gives it color.

Acid Orange, many reds and oranges are shaped like this.
Acid Orange

Acid Green, many if not most greens are shaped like this. Some purples and blues as well.
Acid Green

Acid Blue, this overall elongated structure is what a lot of the “leveling” dyes use.
Acid Blue

A “leveling” dye, is a dye which naturally makes for a more even color coating. The way this is done is by making a dye molecule with weaker binding potential (a weaker south pole) so that molecules can bind and unbind to move about the fiber evenly. This is convenient, but the trade-off is that the dyes can come off the fiber even when you don’t want them to. This is annoying if you want to wash your fiber in warm or hot water.

Another concern that many have with acid dyes is that to get the deeper and intense colors, especially blues, many of them are made with metal ions…

For example, here’s ProChem’s black dye, acid black. It’s a “true black” or “primary black” meaning that it’s not blended. But the intensity of color comes from that “Cr” in the middle of the molecule, which is a Chromium atom. Chromium is a heavy metal, which makes this a dye you don’t want to pour into your groundwater.

Acid Black

(You’ll notice this dye, as well, uses the “sulfonate” SO3 group as its ion, but also has a “nitro” NO2 group as well)

As a rule, companies try to limit the amounts of these heavy metals they need to use, and some companies like Greener Shades try to eliminate them altogether. However, some colors are hard to get without the use of metals.

So, in short…

Acid dyes are anionic (south pole) dyes, which use heat and an acidic environment to form ionic bonds with fiber.

Direct Dyes:

Dyes in this category are…

Cushings Direct Dyes
Jacquard iDye Direct Dyes
ProChem’s Diazol Direct Dyes, now sold by Aljo Mfg.
Any “universal” dye like RIT will have a Direct Dye as one of the two components

Direct dyes also use a combination of forces to bind to fiber…

Primary: van der Waals
Secondary: Hydrogen bonding

You can see already, that in some ways they’re similar to acid dyes, but their primary binding mode utilizes a much weaker interaction. Still, they bind similarly to similar fibers.

Direct dyes tend to be very large in order to have more “subtantivity.” This means having more surface area to contact the fiber and engage in more of these small van der Waals interactions.

Many if not most of the direct dyes will function as acid dyes as well. Look at this Direct Red dye and you’ll see why…

Direct Red

See that SO3 group? Yep, acid dyeing group. The problem with these dyes is that being as long as they are, and generally more balanced along their length, they again are easier to dislodge. You’ll notice it looks almost identical to the “leveling” category of dyes, that’s because… the classes overlap! More on what this means when I get to fiber chemistry in the next Dyeing 101 post.

You’ll also notice there’s more H’s hanging off, hydrogens that can be used in hydrogen bonds to stick this dye to fiber that doesn’t have that “north pole” that the acid binding group (the SO3) needs.

Since these dyes rely generally on weaker interactions, they are less washfast and lightfast than most acid and reactive dyes. Being big and floppy, they also tend to be duller in color (though this trait is not uniform). The advantage of them is that they don’t require fiber with positive “north pole” groups.

So, direct dyes in brief…

Use some ionic, but mostly hydrogen bonding and van der Waals forces to bind to fiber. Less wash and lightfast than reactive or acid dyes, but better leveling and don’t require cationic “north pole” groups to bind.

Reactive dyes:

Dyes in this category…

Procion MX
Dylon Cold
Cibacron F
Prochem Sabracron F
Vinyl Sulfone

Reactive dyes us primarily a singular mode of binding, though most can use another as well.

Primary: Covalent bonds
Secondary: As acid dyes

Covalent bonds are what you think of when you think of molecules. “Actual” bonds. The kind that hold the H-O-H of water together. Those little lines in all these diagrams are covalent bonds.

Covalent bonds are the strongest bonds, as such reactive dyes are the toughest when it comes to being washfast.

I wish there was a better picture of this, but here’s a common reactive dye molecule…

Reactive Red

The first thing you might notice is those SO3 groups. That’s what makes this able to function as an acid dye if you add vinegar.

But here’s the important part of the molecule, over there on the left…


Funny looking bit, isn’t it? Chlorines (note that when on the dye, one chlorine is replaces with the dye)? Negative charges? Those chlorines would really like to rip a hydrogen off of your fiber and float off happily as HCl (Hydrochloric acid), but that would leave that ring behind it bare! But wait, whatever is behind the H the Cl ripped off is ALSO bare, usually an O or an N (Oxygen or Nitrogen) so the two bare things can interact and form a new covalent bond, yay!

That means when the process is done, you have a dye molecule that is actually PART of your fiber molecule, pretty cool? And depending how those interaction groups are designed, they can react with all SORTS of things. Neat. The highly basic environment most reactive dyeing is performed in is to make this process easier, similar in reverse to why acid dyes are done in an acidic environment.

So, an overview of reactive dyes…

Covalently bonded to oxygens and nitrogens on the fiber, making them ultimately washfast. Lightfasteness varies with the structure of the dye molecule.

Disperse Dyes:

Disperse dyes are horrible and gross. They’re what you have to use to dye polyester and acrylic and similar plastics. Ok, that’s not all true. There are ways to dye polyester without having to use the noxious chemicals and super heat, Jacquard has dyes for it. But they’re still not pleasant dyes. I’m not going to talk about the chemistry of these.

Brief overview for those who want the differences quick:

Acid Dyes: Anionic (negative), bind to cationic (positive) fibers. Can’t bind nonionic fibers. Fairly washfast, pretty lightfast.

Direct Dyes: Often anionic (negative) binds to nonionic fibers, and if anionic then it can bind cationic fibers as an acid dye. Not very washfast or lightfast. Many can be used as weak acid dyes. A component in “universal” dyes like RIT

Reactive Dyes: Covalent interactors, often with anionic (negative) bits as well. Given the right environment can bind covalently to nonionic fiber, and possibly to cationic fiber. Many can also function as acid dyes on cationic fiber.

Now, I’m sure by now you’re waiting for me to tell you WHAT fibers are cationic, and what fibers are nonionic. You might be wondering if there’s anionic fibers too. We’ll get to that, but not in this post. That’s in the next post. Cellulose, protein, animal, plant, extruded?

::waves:: As I said above, feel free to ask questions, clarify, or even argue with my chemistry.

Answers to Questions:

To Velma: By wandering around the web a lot. Here’s what I can tell you about ProChem’s stuff…

Sun Yellow, Basic Red, Bright Blue Red, Turqoise, Bright Blue, and National Blue are all non-metallic. Carbon Black (Acid Black 52) is the chromium containing one. Here’s a link which has some minimal information. As a rule, if you Google either the systematic name or the Color Index name, you can find the structures of things. So for example… Acid Yellow 17 Sigma can be a good place to find these.

To Krissy: Usually, that’s how those fibers are dyed, from what I understand. They’re colored in the vat, before extrusion.

Kellie: Feel free to link away. And anyone who comes here from there can also feel free to ask questions or make comments.

Diane: An ionic bond is like a magnet. It can only occur between two things which are magnetizable (or in the case of ionic bonds, things which have charge). So, like you can’t stick a magnet to plastic, you can’t stick an ionic compound to a non-ionic one.

David: The next big post in this series will cover the basic difference between fibers, animal, plant, and others.

~The Gnome

Dyeing 101

A couple people have asked me how I dye.

Now, I hesitate to let the cat out of the bag, but probably not for the reasons most people would expect.

You see, most independent dyers are loathe to make a post like this because their patterns and dyeing methods are all they have to separate them from the scads of other indie dyers out there doing similar work.

But you see, here’s where my real deep, dark, and dirty secret arrives…

I am not those dyers.

I have one trick which I think is uncommon, but that’s because it doesn’t work on a lot of fibers.

I don’t have big secrets of dyeing methodology. I use very basic methods and very basic tricks.

So, how do I get the effects I do?

Easy. I know my fiber and my dye. Really the singular trick to dyeing, whether you want a semi-solid or wildly variegated yarn, is to know your fiber and dye.

This means more than, “I have superwash merino.”

I’ve written before about how I don’t dye scientifically. Perhaps that was a bit disingenuous, because the truth is that while I use dyeing like an impressionist painter’s palette, I cannot (and wouldn’t desire to) escape the fact that I have an academic’s mind.

When I say, “know your fiber” I mean you have to know why things happen like they do. Pick up any introductory dyeing kit or go to one of the dye company pages, head over to knitty and put “dyeing” into the search, and it will give you a set of directions. Great, you can dye now, right?

Wrong. You should, if the directions are well written, be able to reproduce whatever effect (often solids) the directions are written for. Because, if you follow the directions, you are essentially being a machine, there is no understanding.

But what if, instead of leaping in and following the directions, you sat and said, “Huh, why do they say to presoak it? Why do I need to add dawn to the soak?” Then, you’d have understanding of what you were doing, and suddenly you’d not be a machine trying to duplicate a process, you’d be a comprehending artist with the ability to say, “but I want THIS effect so then I should be able to…”

I don’t use fancy tricks. I use very very basic methods, with no fancy ingredients or tools, all in my kitchen, in an oven, one really big canning pot, one medium big heavy stainless pot, and a small stainless pot. Most of my methods use simple resists very much like what you learned at summer camp when you tie dyed a t-shirt.

Because in the end, the real “trick” to dyeing, no matter how fancy the end product, is to know your fiber, know your process, and then to… be creative.

I make the colors I do because that’s what I see in my mind. I could no more describe to you the process by which I look at a wet fiber and say “huh, you know that needs more brown, then it will look much more like the mottle of a sphagnum moss.” than I could describe the reason one rosemary cutting roots while its 10 neighbors just rot off or shrivel up.

That said, I’m going to do a series of posts here about dyeing. I know, I know, I just told you I can’t teach you to dye like me. But see, that’s good! You can dye like you instead! Cool, huh?

So, if you’ve made it this far, you’re probably asking what’s going to be in these posts, right?

As I noted waaaaay up top, before I got all verbose and circuitous, there are a lot of dyeing tutorials out there. Many of them are excellent, so I won’t duplicate them. I will likely link a few, but the actual process of dyeing is not what I’m going to talk about.

I can hear you saying, “Ok, Gnome, so what are you going to talk about? Quit lallygagging and tell us!”

I’m going to talk about the science of dyeing. That is, what things do what, and why. I’m not going to tell you how I do dyeing, I’m going to tell you how i think about dyeing.

Here are some examples, in approximate order:

Dyeing 101: Acid vs Reactive – What’s the Difference between Acid and Reactive Dyes? Direct? What’s that?

Dyeing 101: Animal fibers vs Plant fibers – Protein vs Cellulose and What that Means

Dyeing 101: Fiber Structure – Animal vs Plant Structure

Dyeing 101: Wool Structure – Longwool/Fine wool/Downs wool, Huh?

Dyeing 101: More Structure – Alpaca, Why is it Different? Silk, Why Won’t it Get Wet? Cashmere, Eep?

Dyeing 101: Stuff You Add – Why Detergent? Why am I Soaking it? What’s the Vinegar for? SALT?

Dyeing 101: Things Which Resist – How Pattern Happens

I will try to get to as many of these as possible, they’ll be spaced out as time permits. Because you know I have so very much spare of that.

Also, I am sore. My living room is all reorganized, though not clean yet. I might actually be able to use it. I think I might need to get rid of my spare couch, but I don’t know for sure, or how I’d do it.

That’s it for now.

~The Gnome

Fiber Reactive Dyes

Remember how I mentioned I was gonna talk about fiber reactive dyes ages ago, when I explained how acid dyes work? and then went on to talk a little about things you can do about insolubility?

Well here it is, finally. I was dyeing again (also fnally) last night, and was thinking about this again. This post is a little more chemistry heavy than the last one. Feel free to ask questions if things are unclear.

So, fiber reactive dyes are slightly different than acid dyes. Acid dyes work by loose associations with fiber. So while they are “fast” (don’t tend to wash out) they’re not actually “bound” in the chemical sense. That is, if you drew a picture, there are no hard dark lines between the chemical structure of the dye and that of the fiber, just dotted ones.

Fiber reactive dyes take those loose associations one step further to make actual chemical (covalent) bonds with the fiber. One reason for this is that plant fibers are slightly basic, while animal fibers are slightly acidic. That means that an acid dye (which requires an acidic environment to stick) will never stick to the basic plant fibers.


Here’s an example of a reactive dye. As usual, you can ignore most of it because the really big parts are just to make it have color. The important part is that SO3 part in the top right. That’s our “reactive” group.

This particular dye has a masking group on the reactive part (The Na – sodium – to the right, plus one of the O’s) which prevents the dye from reacting with water (that SO2 sulfur dioxide group LOVES to react with things) until you either boil it or add a very basic compound like soda ash to knock the sodium off. Then the C-SO2 can bond with an C-O-H on the fiber and make C-S-O-C which is muuuuch more stable.

I suppose I should note here that this is not a typical reactive dye, structurally. Most reactive dyes are unmasked and use a slightly different reactive group.

Yellow Procion

This is a Procion Yellow dye. In this, the loops behind the chlorine (Cl) are the reactive groups. The chlorine comes off, and the ring reacts with the cellulose to make an “ether” bond, C-O-C (the corners of the rings are C, carbons). The chlorine (unlike the NaO above) is more than happy to fall off as soon as you add water, so it’s called a “leaving group” instead of being a masking group that has to be knocked off.

Dyes like Procion MX don’t have that masking group, so you can’t put water in them until you’re ready to use them, ’cause that reactive group will react with you water! Then it can’t react with your fiber anymore, and much sadness abounds. However, not having the group means that you don’t have to get the masking group off at all, which means almost all your dye will react with something, even if it’s the water. So, if you’re fast, the non-masked dyes are “more reactive” (more of it will react with your fiber) than the masked dyes.

If you actually want to do fiber reactive dyeing, Knitty has a good article.

~The Gnome