Section 7: Natural Dyes, pH, and Mordants

Indigo dye is one of the oldest known dues dating back more than 5000 years ago. Indigo plantations were found in many parts of the world, from India to the United States. Indigo was first synthesized in 1880, and by 1920 synthetic indigo had virtually replaced all natural indigo. It is still one of the most widely used dyes today- think denim. Small, family-owned farms are on the verge of economic collapse in the United States. The once lucrative cash crops, like tobacco, are no longer good investments for farmers. Since indigo is fairly easy to grow and grows well in the Southern United States, would you recommend it as a potential crop for small farms to replace the use of synthetic indigo? Explain your reasoning.

Yes because people can make money off of it, but it would only be good for small farms and local use, not businesses, because the dye fades and each thing dyed will have a little less color.

Natural Resource

Something, such as a forest, a mineral deposit, or fresh water that is found in nature and is necessary or useful to humans.

Review your procedure and data on the effects of pH on dyes to assist you with this question. Soapy solutions are often very basic in character. What would be the effect of rinsing acid-dyed wool in a soapy solution?

The acid-dyed wool would fade.

Chromophore

The part of the dye molecule responsible for the color.

What is a chromophore?

The part of the dye molecule responsible for the color.

Dye

Typically defined as organic molecules that bond directly to a textile to produce a color.

In textiles, what property must a dye have in order for it to be used?

Water solubility

Autochrome

A functional group attached to a chromophore that enhances the chromophore's ability to absorb light energy. It can alter the wavelength, intensity, or both.

What is an autochrome?

A functional group attached to a chromophore that enhances the chromophore's ability to absorb light energy. It can alter the wavelength, intensity, or both.

Lake

A pigment formed by precipitation of coloring matter with a metal ion.

After treating wool yarn with various mordants and making observations of it, did you notice any difference in the way some of the yarn felt when compared to yarn in other treatments? Why would one of the mordants be less desirable for wool?

Because it would mess with the makeup of the wool

Why might color fade from a brightly colored T-Shirt when it is washed? How does a mordant prevent colors from fading?

Because it's lighter so its easier to fade. Mordants lock down the color.

What criteria did you and your group use to determine good sources of natural dyes? Did the color of the dye material always resemble the color of the dye? What factors might affect the color of a dye?

Deepness and consistency of color, no not always, and how much dye is used, how well it is mixed, etc.

Mordant

Metallic salts added to a dye to make it less likely to wash out.

What is a mordant?

Metallic salts added to a dye to make it less likely to wash out.