Category Archives: chemistry of dyeing

Does chlorinated tap water affect the fibre reactive dye process?

I’m currently doing a lot of Fibre reactive dyeing, and trying to improve my results by fine tuning all the variables.

I’ve looked everywhere for this info, not having any luck. Does chlorinated tap water have any appreciable effect on the fibre reactive dye process? Our water at home is very good well water, but at my studio it’s pretty stinky, yellowish, chlorine filled stuff.

I have a lot of reading to do by the looks of your very informative site! I’m some glad to have found it, and your wealth of knowledge.

Cheers from Atlantic Canada,


Water quality does make a difference. Chlorine’s not the only contaminant involved, if your water is stinky and yellowish. Some contaminants are much more important than others.

Chlorine for disinfecting water supplies can be added as chlorine gas or as hypochlorite (which we call household bleach), or the chlorine compound chloramine can be added instead. Chloramine is more difficult to remove. Chlorine can be removed with hydrogen peroxide, or by evaporation, but chloramine cannot. Both chlorine and chloramine can be removed with Anti-chlor (sodium metabisulfite), which is readily available from dye suppliers, as well as from sellers of supplies for home beer-making and for photography. The same chemicals used for neutralizing chlorinated water are also used for neutralizing chlorine bleach used as a discharge agent; see How can I neutralize the damaging effects of chlorine bleach?.

When my area’s public water supply changed from chlorine to chloramine, we began to notice more fading of clothing, even clothing dyed with good Procion dyes. The colors still last a long time, but a garment that has been washed a hundred times is noticeably paler in color than when it was new. It would help if we were to always add anti-chlor to every washload, but, since our problem is not very severe, we haven’t felt it to be worth the bother.

Dyers often need to be aware of hard water, which is water that contains calcium and/or magnesium ions. (See Dyeing with hard water: water softeners, distilled water, and spring water). These ions are what combine with soap to make soap scum, which has to be scrubbed off of surfaces. Hard water has more than one consequence in dyeing. It can result in colors that are not as bright, it can make it seem as though your soda ash is not dissolving completely even when it is (because of the formation of insoluble calcium carbonate), and it can result in the formation of dye/calcium complexes that are more difficult to wash out of the fabric, resulting in later color bleeding that makes it seem that the dyes are not washfast, when in fact it is only incompletely-washed-out unbound dye. The solution for hard water is easy. Buy sodium hexametaphosphate, also known as water softener. Sometimes sodium hexametaphosphate is sold under the name of Calgon (Jacquard Products still uses the Calgon name on their water softener for dyeing), but beware of other products also sold under the Calgon name, which contain carboxylates rather than phosphates; carboxylates which are not desirable for dyeing. Do not buy any liquid form of Calgon, since these generally contain carboxylates rather than phosphates. Mix sodium hexametaphosphate in the water you use to dissolve your dyes, and in the water you use in your dyebaths; also add it to your wash and rinse water, when washing out excess unattached dye after dyeing. The amount needed varies according to the hardness of your water supply; I can tell you more about this if needed.

Neither chlorine nor hardness will make water yellow. If your water is yellowish in color, it has additional contaminants, which can be a big problem. I’m concerned that you may also have iron. Iron is one of the worst water contaminants for dyeing, though it is safe to consume in the quantities likely to be present. Iron tends to “sadden” many dye colors. It’s used as a mordant with natural dyes to produce dark, dull colors, but it can also affect the colors of synthetic dyes. If your water is contaminated with iron, you probably won’t want to use it for dyeing bright colors. You cannot remove iron with phosphates or with anti-chlor. Water softening systems work well for removing hardness minerals from water, but they do not generally remove large amounts of iron. Specialized water purification systems that can remove iron are more expensive than ordinary water softening systems. A reverse osmosis system would work. You can use distilled or deionized water. Otherwise you may be reduced to bringing water to your studio from home.

To see how severe your problem is in practice, you should do some small scale tests of dyes you like, using only distilled water in one set, while using the stinky yellowish tap water available at your studio in a second set. Perhaps in a third set you could use tap water that you have treated with anti-chlor and hexametaphosphate. I would be interested in knowing how significant the difference turns out to be for you.

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color-changing yarn

LAB wrote:
I recently bought some interesting yarn – it’s a radically different color depending on what sort of light it’s exposed to. I’ve seen this sort of yarn a couple of times from different dyers – it’s fascinating. I’d love to know how it’s done. Would you happen to know?

It’s from the Mystical Moose series, on this site:

This is wonderful stuff! It’s like the gemstone alexandrite, which is green in daylight, but changes to red under incandescant light. The way it works is that the coloring in an alexandrite stone absorbs light in the yellow range of the color spectrum–the color spectrum is the range of colors you see in a rainbow–while allowing you to see light in both the green part of the spectrum and the red part of the spectrum. If the original light that is shone on it contains more red light, like incandescent light bulbs or a candle flame, that that is the light that you see, whereas if the original light contains more green and blue light, such as sunlight or a halogen lightbulb, that is the color you see. The color in alexandrite is provided by small amounts of vanadium or chromium in the gemstone.

You can’t get this effect simply by dyeing with two different dyes, each of which reflects light in one of the two colors you want to see, because dyes, like paints, work in a subtractive way. If you apply a red dye to fabric, it works by absorbing the green light, so all you see is red, whereas if you apply a green dye, it works by absorbing the red light, so all you see is green. If you apply two different dyes, a green one which absorbs red light, and a red one which absorbs green light, the two colors are both subtracted from the light you see, which is why dyeing the same piece with both red and green dye results in a dark brown color.

The only way you can produce the different colors under different lighting is to have both extremes of color reflecting from the same dye, and then compare the effects of a warmer light against those of a cooler light. It’s simply a question of choosing a particular dye that absorbs in the correct parts of the color spectrum. There aren’t many dyes in common use that show this effect so strongly, and I’ve never seen them marketed for this property. Often the property of showing markedly different colors under different lights is considered a defect in a dye, because people want their ordinary clothes to be a predictable color. If you put on a red shirt under an incandescent light at home, you’re not expecting it to turn brown under the cooler fluorescent lights at work. When the special color property of the dye is remarked on at the time of sale, however, what is sometimes a defect instead becomes very desirable. It becomes something you can play with.

I have observed this effect in a subtler form myself. I purchased some of a rather expensive Procion MX dye, red MX-G, also known as Colour Index Red 5, from George Weil in the UK. It is much closer to a true red than our usual red mixing primaries, which are red MX-5B (magenta) and red MX-8B (fuchsia), both of which reflect a large amount of blue light as well as red light. I was trying to decide if it was really a true red, or tilted slightly toward the orange or the blue side of red. It was impossible to decide. When I looked at fabric I had dyed with red MX-G, it seemed to be slightly orangish indoors, but slightly blue under the light of the sky. It was only a mild effect, though, not nearly as extreme as in the Mystical Moose series series of yarn. Red MX-G is not a popular Procion dye, by the way, because it is quite expensive, and yet a very similar color can be obtained much more economically by mixing red MX-5B (magenta) with orange MX-2R (strong orange).

Now obviously all colors are somewhat affected by the color of the light you shine upon them. A dye or pigment has its color because it reflects only a limited portion of the visible spectrum of light, but if the light source contains a different balance of colors, the dye or pigment can’t show you any more light than it receives. Mostly our brains somehow manage to correct for the different colors of light, so that we usually notice the changes only in photography. Why haven’t we noticed the difference between the blue/red balance of a pure fuchsia dye under warm lights versus cool lights? It reflects both blue and red light, after all. The difference is there, but it is far less visible than that of the dramatic variations in the Mystical Moose series of dyed yarn.

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