Getting Pigments to Hang On
Finessing Fibers It's generally easier to dye animal fibers like wool and silk than plant-based fibers like cotton or linen. The scale-like protein molecules in wool fibers provide a lot of active "sites" to which pigment molecules can attach. Cotton, flax, and other plant fibers, on the other hand, are made mostly of smoother cellulose, which has few sites available to combine with color molecules. But, don't take our word for it. Invite your students to carefully observe different types of fibers and fabrics under magnifying lenses. (You may want to include synthetic fabrics as well. Pigments will bind differently to each type of fiber.) Consider numbering each sample and have students, notebooks in hand, describe and/or draw each specimen and compare it with others. (You may want to reveal the origin of each type of fiber.) Which do they predict will more readily "take" a dye and hang onto it? Have them explain their responses and then give them an opportunity to test their assumptions.
Ties That Bind
Students can also design investigations on the mordant effects of other other pantry products, such as sugar and table salt, alone and in combination. Dyeing fabric in brine from pickled beets, which contains sugar and vinegar, or juice from canned beets, which are usually sweetened and salted, produces a truer and more colorfast result than the water from boiled beets.)
Getting their hands dirty with dyes made from flowers, grass, berries, and roots can allow students to experience the wonder likely felt by the ancients who first discovered them. You can use the experience to pique their curiosity about the significance of dye colors to various cultures, and the history of dye technology throughout the millennia. Ask your young explorers to imagine and discuss how they think early humans might have discovered that they could use plant pigments to color their bodies, hair, crafts, animal skins, and fabrics. Encourage exploration through library and Internet research, or better yet, ask an experienced craft dyer or folklife educator to speak to your class. Students might feature their discoveries in a story or a play, develop a presentation for younger students, or otherwise demonstrate what they've learned. (For an example of how a group of 6th graders approached this adventure, visit Making Dyes Naturally.)
Across the Curriculum
Your students can uncover "hidden" colors in leaves through a process called chromatography. In chromatography, a solvent carries pigments up a paper strip, with some will "dropping out" of the solution sooner than others. Because each pigment has a characteristic rate of movement, they will separate from each other on the strip, typically as green, yellow, and light orange bands.
1. Invite students to collect and keep track of leaves from different types of trees and locations (e.g., shade and sun).
2. Crush the leaves and put each type in a test tube or small, lidded glass jar. Carefully add enough of the solvent acetone (you can use nail polish remover) to create a milkshake consistency (for a test tube, this will be about 2 cm). Cover and let the mixtures sit for 24 hours to allow pigment molecules to dissolve in the acetone.
3. Make narrow strips from the middle of a coffee filter, then place one end in each solution and let it sit overnight.
4. Remove the strips and let them dry, making sure they don't get mixed up.
Ask, What conclusions, inferences, and new questions do you have? Did some leaves have the same mix of pigments? Were they similar in other ways? Did sunlight seem to make a difference? Would you expect to get the same results all year round? How might the colors in tree leaves compare with those in garden plant leaves, such as spinach? (Find out!)
another school through our Garden
in Every School registry that is willing to exchange data on a
leaf pigment project.
Before synthetic pigments were available, colorful fabric tended to be expensive and hard to come by. The same is true for food colorings. Our ancestors' records suggest that specially colored food was mostly for the well-to-do, although one favorite of the Colonial American masses -- pancakes -- were tinted pink with beet juice! Most food colors were derived from edible berries, flowers, and even medicinal lichens. Some food dyes weren't even edible, but people tried all kinds of combinations in the quest for fashionable foods (For details, visit Elise Fleming's Web page on Food Coloring Agents.)
Natural food dyes generally impart the flavor of their source (not always a good thing!), but synthetic food colorings have no flavor. However, synthetic food coloring has been the object of investigation by consumer advocates for decades because of their potential (and established) health risks. This issue can provide fertile ground for more student research into the history of food marketing and safety issues. To conclude their analysis, suggest that the class holds a cook-off to compare natural food dyes (known to be absolutely safe) with synthetic ones. The event might feature baked goods, herb teas, ice cream, or other snacks tinted with fruit and vegetable juices or edible flowers (e.g., rose petals, violas, nasturtiums) as well as bottled food coloring.
Pg. 1: Dyeing with Plants
just published this new book filled with actual school garden
plans, stories of how students participated in the design process,
how-to information, and resources.