Name: Afif

Country: Malaysia

Message: I'm doing a chemistry project about batik. What is the best fabric that can be used with natural dye (grape), fibre reactive dye, and food colouring, among silk, cotton and nylon? Does the chemical bond related to this case?

The easiest to dye fabric among these three, cotton, silk, and nylon, is certainly silk. Silk is uniquely easy to dye, because it can be dyed just like cotton, or just like wool. Normally there is little intersection between the dyes used for cotton and the dyes used for wool; cotton dyes react with cellulose, while wool dyes react with protein. (Wool will react with cellulose dyes, but wool is damaged by the conditions that are used to dye cotton.) Silk is more resistant to high pH and will dye well with any cotton dye, but since it is composed of protein, like wool, it will also dye well with the acid dyes that work well on wool. Nylon is an interesting case, having chemical linkages similar to those between the amino acids in any protein; it will dye with most wool dyes, but not, generally, with cotton dyes. Nylon usually stays white when treated with cotton dyes at high pH, unlike wool and silk. All of which is just to say, I recommend that you use silk if you want to be able to dye it with the widest possible range of dyes. Comparing the same dye on different fibers will make another good chemistry project.

Cotton forms a different type of bond to fiber reactive dyes than it does to natural dyes, and it will not form the same kinds of bond that protein fibers can form, with acid dyes. For more information on how different types of dyes bond chemically to textile fibers, see "What kinds of chemical bonds attach dyes to fibers?".

Grapes make an extremely poor natural dye; in fact, I would not consider it much of a dye at all, merely an unwanted stain. The purple color of a grape is provided by chemicals called anthocyanins, which turn dull in color when you wash the dyed item. I would recommend a better natural dye, such as powdered turmeric root (which you can buy the the spice section of the grocery store) or cochineal (which, at least in the Unites States, can be purchased by mail-order from a natural dyes supplier) or the hulls of nuts such as pecans or walnuts (which you can gather if you have a tree nearby). You can use pomegranates for a brown dye. In each case, except for turmeric, you should use a large amount of the dyestuff. Weight the dry fabric that you are planning to dye, and then use an equal weight, or even two or three times as much, of the dyestuff, as the weight of your fabric.

However, all of these dyes that I have mentioned so far, and indeed most natural dyes in general, require heat to bond to the fiber, preferably boiling the fabric in the dye for some time. This treatment will cause the wax used in batik to melt. Natural dyes that can be used in cool water are generally very difficult for a novice dyer to use. The natural dye indigo (often used in its synthetic form), which works well in room-temperature water and has therefore been used in batik for many generations, is too much of a challenge for novice dyers for it to be appropriate for a student project. It might be best, for your project, to skip the wax resist used in batik, and merely test how well the dyes work on your choice of fiber. 

Most natural dyes will not bond to fibers in their natural state. Instead, you must first apply a mordant to the fiber, usually a salt of aluminum, tin, copper, or iron, by cooking the dye with the mordant. Only after this process can you apply the natural dye by cooking it with the mordanted fabric. Alum is the most popular mordant, because it is less able to be dangerous to people who misuse it; even alum can be fatal, but the fatal dosage for an adult is about 30 grams. If you are careful in how you use it, and keep it out of the reach of children and pets, you can use alum safely. The natural dyes bond to the metal ion, which has bonded to the fiber. Most natural dyes will not bond directly to the fiber, or at least not permanently. Exceptions to this rule include turmeric, walnut, and, I think, pomegranate, though each of these will work better and last longer if you mordant the fabric before dyeing it.

Food coloring cannot be used to dye cotton at all. If you want to try dyeing with food coloring, silk and wool are by far the best choices (wool better than silk, in fact). Food coloring falls into the category of textile dyes known as acid dyes, which can be used only on protein-based fibers, such as silk and wool. See my page on "Using Food Coloring as a Textile Dye for Protein Fibers". You will need to use a mild acid, such as vinegar, diluted in water, and you will need to heat the fabric in the dye, in a pot on the stove. When heating silk, do not bring the dye bath liquid to a full boil (with big bubbles), because the high temperature can damage the silk. Keep the water no hotter than a simmer, about 87°C, in which only tiny bubbles rise at the edge of the pot. Note that aluminum cooking pots will react with acids such as vinegar, and also with bases such as soda ash, so it is best to use a pot that is made of stainless steel or enamel to heat your dyes.

Fiber reactive dye is extremely easy to use, with a high-pH chemical such as soda ash, on both cotton and silk; if you treat it as an acid dye, by using vinegar instead of the soda ash normally used, it will also work on nylon. Silk will take fiber reactive dye under the high-pH conditions required for cotton, using a chemical such as soda ash or washing soda to fix the dye. You can also used an entirely different method, using an acid such as vinegar, and applying heat. Either method will work well on silk. (Just don't do both!) I like to dye silk with fiber reactive dyes in the presence of soda ash, because it is very easy to dye it this way, since no added heat is required, so you don't have to cook the dye reaction on top of the stove. You can dye silk with fiber reactive dye in a bucket, or in a plastic bag, or by squirting the dye on the soda-ash-soaked fabric exactly as in tie-dye. (See "How to Dye with Fiber Reactive Dyes".) Any of these methods will work well, as long as you use soda ash or washing soda. I don't know which of the fiber reactive dyes is easiest to buy where you are. Remazol, Drimarene K, and Procion dyes are the most commonly available. If you are not sure whether the dye you buy is fiber reactive, write to me with all of the information you have on the label and I will try to figure it out.

Good luck with your project.