Country: USA

Message: I am tie-dyeing infant clothes w/ alum & cream of tartar as a mordant(using dyestuff that consists of natural food products: i.e. organic tea, organic beets, turmeric, etc.). Recently I read that alum is unsafe, especially b/c babies have a tendency to chew and gnaw on their clothes - have you any suggestions as to what would be the best mordant subsitute esp. b/c I wish to continue naturally dyeing? Might citric acid and washing soda be better?

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The only good answer for you, if you want to use natural dyes, without alum or other mordants, to dye clothing for infants in bright colors that last through the laundry, is to dye with natural indigo. It's a challenging dye to work with, much more difficult to use than a synthetic fiber reactive dye, but it is truly an excellent dye, and, unlike other natural dyes, does not require a mordant. Some particles of indigo will eventually work their way out of the fiber into the baby's mouth, unlike properly applied fiber reactive dyes, but indigo, in the form of FD&C blue #2, has been tested for safety when used as a food coloring, so this is less of a problem than your alum, which is irritating and not good for a baby to chew on. 

Although alum is traditionally used to make pickles extra crisp, it has never been approved by the FDA for this purpose, and the FDA recommends that alum never be used in any food product. It is highly misleading when people who sell hand-dyed baby clothes refer to "food grade" alum, implying that it is safer than it really is. The fatal dose of alum for an adult is one ounce, or 30 grams. The fatal dose for a 15-pound infant might be one tenth that amount, or 3 grams; of course, the amount that will irritate the skin or digestive tract is considerably smaller than the fatal dose. However, alum is by far the safest of the effective mordants used for dyeing with natural dyes. Tannic acid can be used as a mordant, but the best way to mordant cotton for natural dyes is to treat it first with alum, then with tannic acid, and finally with alum again. Tannic acid alone is not nearly as effective, as a mordant, as tannic acid plus alum. Other good mordants, including copper, iron, tin, and chromium, are poisonous and therefore entirely unsuitable for use in dyeing baby clothes.

Synthetic fiber reactive dyes, such as Procion and Remazol dyes, are very safe dyes to use on cotton baby clothes, because of the way that they bond permanently to the fiber, so that they cannot come off in the baby's mouth. They are much easier for the novice tie-dyer to use than natural dyes, and they stay bright for years longer. There is no need for mordants with fiber reactive dyes, because they react directly with the fiber itself, in the presence of washing soda.

Neither citric acid nor washing soda are mordants. See "What's the difference between mordants and other chemical assistants used in dyeing?". Citric acid's only purpose, in dyeing, is to lower the pH of the dyebath, increasing its acidity, which is of no use in dyeing cotton. Washing soda's only purpose is to increase the pH of the dyebath, which is great for synthetic fiber reactive dyes, but useless for other classes of dyes. If you use citric acid and washing soda together, they will cancel each other out, resulting in a neutral pH, so they'll do nothing at all. Cream of tartar is not a mordant, either; it's just an acid, and, as with citric acid, its only purpose is to reduce the pH, which does not cause any dye to bond to cotton. 

Beets are not a dye. Beets are the most useless plants to use as a dye, because their beautiful red color has no affinity for textile fibers. The most you can get from it, after laundering the clothes you dye with it, is a dull tan color, and that only on wool, not on cotton. Forget about using beets as a dye. See "Beets as a natural dye".

A much better natural red dye is cochineal, made from the bodies of a type of cactus-eating insect. Cochineal will not work on cotton without a real mordant, though. See "Cochineal is a fine dye".

Tea is all right as a temporary light brown dye. It will gradually wash out, so it's not very suitable for anything that must be washed frequently, such as baby clothes. Turmeric is a nice yellow dye, even without a mordant, but fades rapidly in the light. The energy that comes from visible light causes turmeric to fade. Anything dyed with turmeric should be dried indoors only, stored in a dark place when not in use, and redyed every year or so. See "How can I improve the light fastness of turmeric dye?".

There is no effective mordant that is as safe for baby clothes as synthetic fiber reactive dyes, which do not need a mordant. Fiber reactive dyes form a permanent bond to the fiber, unlike any mordant or natural dye, so if all excess unattached dye has been properly washed out, there is no way for the reactive dye to contaminate the baby's mouth, even if the baby chews on clothing dyed with it. In contrast, all mordants will, to at least a tiny extent, leach out of fabric into a baby's digestive system, if the baby chews on fabric that has been dyed with a mordant. If you want to use a good dye for cotton or bamboo baby clothes, the safest choice is fiber reactive dye. Indigo is the only long-lasting bright-colored natural dye that works well on cotton without a mordant.

Indigo does not require a mordant, because its chemistry is very different from other dyes. You must use harsh chemicals, lye and reducing agents, to dissolve the dye so that it can penetrate inside the fiber. Unlike mordants, the auxiliary chemicals are entirely removed by the time dyeing is complete, however, so they do not provide any danger at all to the wearer of the clothing.

Most indigo is synthetic. You can buy a very nice kit for dyeing clothes with synthetic indigo. Natural indigo is chemically identical to synthetic indigo, and is used in exactly the same way, using the same chemicals to dissolve and apply it. You will probably want to get a good book on dyeing with indigo. It will take you some trial and error to get good at dyeing with indigo. You must not attempt to dye anything dark with indigo in one dip, because using too much indigo will result in dye that rubs off of the fabric onto everything it touches. Instead, to get a bright indigo, dip the same piece into the indigo dye bath repeatedly. Do a lot of practice dyeing to make sure that you are able to get the indigo to work right, without rubbing off when it's dry, before you try producing indigo baby clothes. Indigo is not the easiest dye to use, but it is the only dye that meets all of your requirements.

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