Name: Donna
Message: hi,
my name is donna and I am doing a science project on using Kool-Aid as a dye for cotton yarn and how different conditions can result in a more intense color. one of these conditions is pre-wetting the yarn in water before soaking it in the Kool-Aid dye. i've found that pre-wetting the yarn has a great effect on color intensity than not pre-wetting it. i was wondering if u know why this is so and the chemistry behind it. it'll be great if u can get back to me as soon as possible. thank you so much!

First, an important point: you cannot use Kool-aid to truly dye cotton! Kool-aid is colored with acid dyes, which work on wool, but not on cotton. At best, you can only stain the cotton. This is not dyeing. Dyeing requires the dye to actually make a long-lasting bond of some sort to the fiber. If it washes out, it is not dyeing. It is just temporarily dirtying the yarn.

If you want to dye with Kool-aid, get yarn that is made of protein or polyamide, which means, wool or silk or nylon (but no other synthetics). Wool and silk are both made of proteins, secreted by animals. Food colorings are acid dyes, and are no good for plant (cellulose) fibers such as cotton. They work quite well on wool, however. Why don't you go buy some wool yarn, and use it for your project? Kool-aid makes a fine dye for wool, and wool yarn is easy to find in stores.

However, it is, of course, possible to investigate how best to penetrate cotton with a temporary stain, although the practical applications are highly limited. Of course you get a darker color when your coloring material better penetrates the yarn, regardless of what material the yarn is made of. The issue is hydrogen bonding. Hydrogen bonding is what makes it possible to fill a glass of water slightly above the top; it bulges out above the top of the glass without spilling, because water molecules are attracted to other water molecules, helping the mass of water to cling together. It also makes water not "want" to leave other water molecules in order to penetrate yarn. Once the yarn is wet, hydrogen bonding no longer keeps water from being attracted to the yarn. Pre-wetting the fiber makes it easier for the dye to penetrate it.

You should see an even greater effect if you pre-wet with water that has a small amount of detergent *or* rinse agent dissolved in it. Rinse agent is the stuff used to help prevent water spots on glasses in the dishwasher; a popular brand is Jet Dry. Both rinsing agents and detergents help water (or dye dissolved in water) to penetrate the fiber; they do this by reducing the hydrogen bonding forces in the water, which make it want to stick to itself, rather than to anything else. Just a drop or two should be sufficient. If you use detergent, use hand dishwashing liquid, not dishwasher detergent, because dishwasher detergent is quite caustic, and so is rather dangerous to handle, although it does not work any better for your purposes than hand dishwashing liquid.