My name is Rebekah. I am planning to do a science fair project about dyes. Particularly I am interested in natural dyes. Are natural dyes much better that cormecial dyes? Why? Are cormecial dyes harmful to our health? Thank you.

No, natural dyes are not in any way better than the best synthetic dyes. They are less permanent, more difficult to apply, wash out more easily, and often involve the use of highly toxic mordants. Not all mordants are as toxic (e.g., alum is relatively safe to use, though not completely non-toxic) but the truly dangerous mordants such as chromium are required for some of the brighter colors. A mordant is a chemical, usually a metal, which must be used in treating the fabric before applying a natural dye, because otherwise the natural dye will not stick to the fabric. Modern synthetic dyes do not require the use of a mordant.

Some commercial dyes are harmful to health; others are not. Like the chemicals found in nature, synthetic dyes range from harmless to quite toxic. While food dyes, for example, may not be one of the healthier parts of a diet when eaten in excess or by allergic individuals, they have been throughly tested and are quite safe when used in small quantities or when used for external use, such as in dyeing wool (they do not work on cotton). Many different types of dyes have been discovered and used in the past without regard for their possible toxicity, such as the Naphthol dyes, which are popular in Indonesian batik but which are not available for use by dye artists in the United States, apparently due to worries about their possibly causing cancer.

The dyes we recommend for use on cotton, the fiber reactive dyes, are considered unsafe when eaten or inhaled; however, one should never eat or inhale any art materials! (Artist's oils are extremely dangerous, being colored in many cases with toxic heavy metals, and misuse of solvents can be fatal.) The major risk from inhalation of fiber reactive dyes is the development of an allergy to the dye, possibly resulting in asthma, which is treated by completely avoiding exposure to that dye when working with dye in the future. There is also a hypothetical risk of cancer or other toxic effects whenever any product which has not been tested for safety in food is eaten, or inhaled, in spite of the lack of safety testing.

The chemicals used with fiber reactive dyes are, on the whole, quite safe. The soda ash or washing soda (sodium carbonate) which is used to increase the pH of the dye reaction, so that cotton can be dyed, is harsh and drying to the skin and should not be allowed to contact the skin for extensive periods (wear gloves, and wash it off right away after accidental contact); however it is not toxic when sufficiently diluted or neutralized with an acid such as vinegar. Another chemical commonly used in fiber reactive dyeing is ordinary table salt, which is used only for immersion dyeing, never for tie-dyeing. Urea is commonly used in tie-deying; urea is quite safe, and is beneficial as an ingredient in skin moisturizers.

All-purpose dye is another, more common, type of dye besides the fiber reactive dyes (I prefer the fiber reactive dyes). The all-purpose dye sold under such brand names as "Rit Tint and Dye" and "Tintex Hot Water Dye" contains two types of dye: "direct" dye and "acid" dye. You can read about this dye on my web site, under "About Dyes". All-purpose dye is not safer than other dyes. In the book Fabric Painting and Dyeing for the Theatre, by Deborah Dryden, there is mention of a carcinogenic dye, Direct Black, which is known to have been at one time included in all-purpose dyes. Since the companies that sell all-purpose dye, such as Rit, do not reveal which dyes are contained in their mixtures, it is impossible to know whether or not this dye has been removed from their formulations. In any case, the same strict precautions must be taken when using all-purpose dye: never breathe or eat it, always wear gloves, and never use a cooking pot with these dyes that you will in the future use for food. Once dye has been used in any kitchen equipment, that equipment is no longer suitable for use in cooking or serving food. This warning is true for all dyes, whether natural or synthetic.

Procion MX dye is much better than natural dyes or commercial all-purpose dyes, if you are dyeing cellulose fibers such as cotton, linen, or rayon, because garments dyed with it can be washed repeatedly, even in hot water, without removing the dye from the fiber, because the dye actually forms a strong covalent bond to the cellulose molecule.

Another way in which Procion MX dye is superior to natural dye, when dyeing cotton or other cellulose fibers, or in dyeing silk, is that is does not require the use of heat, so there is no need to spoil an expensive cooking pot, and the serious dangers of scalding yourself are completely absent. Both natural dye and all-purpose dye require the use of hot water.

A third area of superiority for Procion MX dyes is the incredible range of colors that may be produced with ease, from neon-bright to subtle earth tones. The color range is considerably better than that found in all-purpose dye, or of course natural dyes.

A fourth way in which Procion MX dye is superior to natural dye, for cellulose fiber, is that the chemicals used with it are relatively safe, the only danger being from careless contact with the skin-irritating properties of the high pH of soda ash (also known as washing soda). This is much better than the dangers of many mordants.

Note that I repeatedly say "when dyeing cotton" or "for cellulose fibers". This is because the different types of fiber are very different in their requirements for dyes. Natural dyes tend to be easier to use on animal fibers such as wool, though mordanting is still required. So are food dyes and other acid dyes; it is a great mistake to try to dye cotton with food dye, but food dye works a lot better on wool. Animal fibers are dyed with acid, not soda ash, whether one is dyeing with Procion MX dyes, all-purpose dyes, or food dyes; acid dyes also require heating. However, in dyeing animal fibers, commercial acid dye is easier to use than natural dye, and frequently less expensive since much smaller quantities of dyestuff are required.

One real advantage of natural dye is that it can be a tremendously fun project to learn how to use natural dyes. The other great advantage is the sheer aesthetic pleasure of using plantstuffs you harvest for yourself, instead of the mysterious products of a factory. Natural dyeing is also a great deal of work, and requires specialized equipment (such as dedicated cooking pots that are never used for food). It is critical to observe all safety measures for whichever dye you use, especially the safety measures required when dyeing with dangerous heavy metals such as chromium, iron, copper, and tin.

It is a foolish waste of time to attempt to dye with colorful items found around the house, such as berries or beets, without first finding out whether or not the substances involved are likely to be capable of making good dyes. It is not uncommon, for example, for someone to imagine that the lovely color found in the water when cooking beets will make a good red dye on cotton; of course, the color just washes away, if special dyeing techniques are not used, and even with proper dyeing technique, the dye from beets turns out to be more likely to be a dull yellow than any kind of red at all. I strongly recommend that you locate some good books on natural dyeing before you attempt to do any natural dyeing at all. I recommend the 2003 edition of Jill Goodwin's A Dyer's Manual. (See book reviews.)

Note that all of the above information is for dyeing natural fibers only. Nylon can be dyed like wool, and rayon or Tencel like cotton, but other synthetics, such as polyester, acetate or acrylic, cannot be dyed with any of the dyes mentioned above. Only special dyes designed for use on synthetic fibers can be used, such as the class of dye known as "disperse" dye. Disperse dye is more allergenic than other dyes, sometimes causing reactions even among the wearers of the garments not just among the people who apply the dye. It is also quite difficult to apply, and is not suitable for use by novices or students.