Name: Gifty

Message: What is the difference between these all purpose dyes and synthetic indigo dye? I know that the natural plant based indigo dyes are not used anymore. Can a rit blue denim dye be used interchangeably with synthetic indigo dye? Are they similar chemically? What are their differences? Can I refer to rit denim blue dye as indigo dye? What dyes are used for blue jeans/denim currently?

Natural indigo from plants is no longer used by the textile industry, but the same kind of dye from another source is still used industrially in huge amounts. Synthetic indigo is identical to natural indigo and is used to dye the blue warp threads that are woven with white weft threads to make the blue denim used in blue jeans. Natural indigo is still available to home dyers and is very popular among those who are expert at dyeing, but it is more difficult to use than other kinds of dye. Beginning dyers should use other kinds of dye. For more information about this class of dye, see "About Vat Dyes"; for more information on how indigo (whether synthetic or natural) is fixed to fibers, see "How do you fix indigo dye?".

"All-purpose" dye, such as Rit dye, is completely different. You should not refer to fabric you have dyed with Rit dye as indigo-dyed; doing so would be misleading, and possibly illegal if you are selling the garment, though you can describe the color of anything you like as being indigo blue. Indigo refers to a specific chemical, which is very different in both molecular structure and in how it attaches to the fiber. Unlike all other classes of dyes, vat dyes, including indigo, have a neutral charge. Other kinds of dye, including both the acid dyes and the direct dyes which are combined in the all-purpose dye mixture, as well as the fiber reactive dyes I recommend instead, have negative ionic charges. The biggest difference between these different types of dye lies in how they attach to your fiber. Indigo is held inside the fiber by being oxidized to a form which is not soluble in water; acid dyes are held to silk and wool (but not to cotton) by ionic bonds; direct dyes are attracted to cellulose by substantivity; and fiber reactive dyes form permanent covalent bonds to cellulose and other fibers. See "What kinds of chemical bonds attach dyes to fibers?".

All-purpose dye will dye many kinds of fiber, but most of them not very well. I do not recommend that you use all-purpose dye on cotton, because there are much better dyes available, which are easier to use correctly. The problem with all-purpose dye is that it does not bond very tightly to cotton, so it bleeds in the laundry every time you wash it, and the color fades away quickly. You can make it more permanent by using a cationic dye fixative, such as Retayne, but this product is difficult to find except by mail-order; if you're going to the trouble of mail-order, you should buy a higher quality dye, instead. See "Choosing the Right Dye for your Fiber".

Instead of either real indigo or all-purpose dye, if you are dyeing cotton, linen, hemp, or other natural fibers, I recommend that you use a completely different type of dye, which is called fiber reactive dye. There are several different types available, but all of them will last many times longer on your fabric before it fades. The brand that is available in the most different colors, and for the cheapest prices, is called Procion MX dye; it is fixed to the fabric at room temperature with soda ash or washing soda, so it is very easy to use. You can buy Procion MX dye by mail-order from suppliers such as Dharma Trading Company (the most economical source), as well as from art supply companies such as Blick Art Materials. You can also buy fiber reactive dyes in a good local crafts store. Look for Dylon Permanent dye, or Dylon Cold Water dye, or Tulip One Step Fashion Dye. In Europe and Australia, look for Dylon Machine dye, which is another brand of fiber reactive dye packaged for use in front-loading washing machines; it's not available in North America. Each of these dyes will last far longer on your fabric, through many more launderings, than all-purpose dye.

When you are sufficiently experienced with the easier-to-use dyes, you should then try dyeing with real indigo, if you're interested. Before getting started, please get a book that will tell you in detail how to manage the more complicated chemistry of the indigo dye bath. Indigo is a wonderful dye, but more challenging to use correctly than the fiber reactive dyes that are ideal for the complete novice at dyeing.

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