Teacher Notes

The Natural Science of Fabric Dyeing

Guided-Inquiry Kit

Materials Included In Kit

Aluminum potassium sulfate (alum), AlK(SO4)2•12H2O, 5 g
Copper(II) nitrate solution, Cu(NO3)2, 0.1 M, 10 mL
Iron(III) chloride, FeCl6H2O, 5 g
Red cabbage extract, 2 g
Boiling stones, 5 g
Tea bags, black, 4
Tea bags, cranberry apple (herbal), 4
Multifiber test fabric, 24"*
Weighing dishes, large, 20
*Cut into 4-cm strips, one for each group, and a 2-cm strip for Part A of the Procedure.

Additional Materials Required

Water, distilled or deionized*
Tap water*
Balance, 0.1-g†
Beakers, borosilicate glass, 400-mL, 2*
Beaker, borosilicate glass, 400-mL†
Colored pencils (optional)*
Graduated cylinder, 25-mL†
Hot plate or laboratory microwave*‡
Paper towels*
Pencil*
Permanent marker*
Scissors*
Stirring rod†
Tongs or forceps*
Weighing dish or paper†
*for each lab group
for Prelab Preparation
See Lab Hints.

Prelab Preparation

For Part A
(Prepare one to three days prior to the lab activity.)

  1. Add 200 mL of distilled water to a 400-mL beaker. Add two black tea bags.
  2. Place 3 boiling stones in the tea solution and heat to near boiling on a hot plate (or use a laboratory microwave).
  3. Reduce the heat and simmer the tea for 15 minutes. Remove the tea bags. Keep the dye bath hot, but not boiling. Note: The tea solution may be prepared 1–3 days in advance and stored at room temperature.
  4. Wet one 2-cm strip of the multifiber test fabric with distilled water.
  5. Using tongs, place the wet fabric strip into the black tea solution. Continue to simmer the tea for another 15 minutes.
  6. Using tongs, remove the fabric strip from the dye bath. Pat with paper towels and then rinse under running water from a faucet until all of the excess dye has been removed and the rinse water is colorless.
  7. Place the rinsed test strip on a paper towel and allow it to dry completely.
  8. If the black tea dye bath is to be used again, it may be stored and re-heated the day of the lab.
For Student Experiments
Directions are given for preparing 200 mL of each solution, enough for 3 to 4 test strips. Amounts may be adjusted to accommodate fewer or more test strips.
  • Black tea: Follow steps 1–3 from Part A.
  • Herbal tea: Follow steps 1–3 from Part A, using two bags of cranberry apple tea for each dye bath. 
  • Red cabbage: Add 200 mL of distilled water to a 400-mL beaker. Measure and stir in 0.4 g of red cabbage extract. Heating is optional. 
  • Aluminum Potassium Sulfate (Alum): For pretreatment, stir 1 g of alum in 200-mL of distilled water in a 400-mL beaker and heat according to steps 2 and 3 in Part A. For treatment during the dye process, add 1 g of alum directly to the selected 200-mL dye bath. 
  • Copper(II) Nitrate Solution: For pretreatment, add 10 mL of 0.1 M Cu(NO3)2 to 190 mL of distilled water and heat according to steps 2 and 3 in Part A. For treatment during the dye process, add 10 mL of 0.1 M copper(II) nitrate solution directly to the selected 200-mL dye bath. Note: Students should add 10 mL of distilled water to the control bath for equal volumes of each bath. 
  • Iron(III) Chloride: For pretreatment, dissolve 1 g of FeCl3•6H2O in 200 mL of distilled water in a 400-mL beaker and heat according to steps 2 and 3 in Part A. For treatment during the dye process, add 1 g of iron(III) chloride directly to the selected 200-mL dye bath. Note: Heating is optional if the mordant is added to the red cabbage dye bath.

Safety Precautions

All food-grade items used in the lab are considered laboratory chemicals and are for lab use only. The dyes will stain skin and clothing. The dye baths are very hot, near boiling. Exercise care to avoid skin burns. Avoid contact of all chemicals with eyes and skin. Use boiling stones in the hot dye and mordant baths to prevent bumping (sudden, violent boiling). Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The dye solutions may be washed down the drain with plenty of water according to Flinn Suggested Disposal Method #26b. Aluminum potassium sulfate and iron(III) chloride may be disposed of in the regular trash according to Flinn Suggested Disposal Method #26a.

Lab Hints

  • Enough materials are provided in this kit for 30 students working in groups of three or for 10 groups of students. Both parts of this laboratory activity may reasonably be completed in one 50-minute class period if the prelaboratory assignment is completed before coming to lab. The data compilation and questions may be completed the day after the lab once the fabric strips are dry.
  • The number of experiments is limited only by the lab equipment available. You may decide to allow one experiment per class, or have each group do a different test. A 7" x 7" hot plate can heat up to three 400-mL beakers.
  • Dye baths left to simmer on a hot plate for more than 15 minutes may be loosely covered with aluminum foil to reduce evaporation.
  • If a laboratory microwave is used, heat the dye or mordant bath just to boiling. Be sure to use boiling stones in each dye bath. Next carefully cover the beaker with waxed paper and then heat the dye bath on 30% power for 15 minutes. Continue heating on 30% power with the fabric strips for the amount of time decided upon, up to an additional 15 minutes.
  • An option for hot water is to use a hot pot or coffee percolator. Dispense the hot water into the beaker just prior to adding the dye source. Wear heat resistant gloves! The water should remain hot enough in the 15–20 minutes needed for the dye to take.
  • If heating the dye baths presents a problem, consider using the red cabbage extract. In our experience, both the room temperature and hot red cabbage dye baths were effective, albeit with different results.
  • Place lots of paper towels or absorbent lab mats all around the dye baths. This will help keep the room clean. Instruct students to store books, bags, and other personal items away from the lab area to avoid staining them.
  • The multifiber test fabric (Flinn Catalog No. AP6135) is fairly expensive but the color patterns are beautiful and intriguing. To save money, the teacher may wish to dye more test strips as part of a demonstration and have students bring fabrics of their own choosing to dye during the experiment. Suitable white fabrics from home include cotton T-shirts, acrylic socks or yarn, polyester sheets, etc. Scavenge fabric stores for inexpensive bolts of white cloth (read the labels!). Pure (100%) white cotton, polyester, acetate, and nylon are easy to find and relatively inexpensive. Wash fabrics before dying to remove sizing and other fabric finishes.
  • The red cabbage dye bath may produce an unpleasant odor over time. Dispose of leftover solution once the dyeing process has been completed.

Teacher Tips

  • This is an excellent and intriguing activity to reinforce the concept of experimental design and controlled investigations. It can also be used as an introduction to chemical bonding. A basic understanding of ionic bonding and polar molecules is all that is needed. Students can truly appreciate the natural science of chemistry with the beautiful results of this lab!
  • Students may experiment with other plant dyes. In our experience, fresh green carrot tops produced bright yellows, fresh marigold and coreopsis flower petals produced beautiful oranges and yellows, yellow onion skin (the papery outer layer) produced interesting gold colors and even green with alum, red roses gave surprising results (not red!), and fresh blueberries (about 6 mashed per 100 mL of water) produced an amazing variety of pink, lavender, purple, reddish purple and bluish purple. Only polyester did not take the blueberry dye, even after allowing the fabric to remain in the dye bath overnight. Fresh flowers produced better results than dried.
  • More intense colors usually result by allowing the fabric strips to remain in the dye baths overnight. Continued heating beyond 15 minutes is not necessary. Cover the cooled dye baths with plastic wrap or Parafilm M® (available from Flinn Scientific, Catalog No. AP1501) and store where they will not be disturbed.
  • Invite the students to examine a predyed multifiber test fabric strip under a magnifying lens or stereoscope.
  • Red cabbage contains a water-soluble pigment called anthocyanin. A solution prepared from red cabbage extract acts as an indicator because it will react with various solutions and the dye bath will change color depending on the pH. Reds and pinks indicate a lower pH (more acidic), lavenders and blues indicate a neutral pH, and greens indicate a high pH (more basic).
  • Many websites are devoted to natural dyeing and contain several tips for types of plant material to use and other suggested mordants. One suggestion we found and tried was adding cream of tartar (0.5 g) in addition to the alum. The biggest difference was found with wool and nylon using the red cabbage dye bath. Both fabrics produced a pink hue. See the Sample Data table for results using red cabbage with alum alone. Another recommendation tested was pretreating the fabric with soda ash (NaCO3, available from Flinn Scientific, Catalog No. S0054). This had little effect with the teas and a modest effect with the red cabbage. However, the same pretreatment dramatically changed the color of wool and acetate using a fresh yellow flower known as biden. As previously stated, the variables are almost limitless and the results often surprising!

Correlation to Next Generation Science Standards (NGSS)

Science & Engineering Practices

Planning and carrying out investigations

Disciplinary Core Ideas

MS-PS1.B: Chemical Reactions
MS-ETS1.B: Developing Possible Solutions
HS-PS1.B: Chemical Reactions
HS-ETS1.A: Defining and Delimiting Engineering Problems

Crosscutting Concepts

Cause and effect
Structure and function

Performance Expectations

MS-PS1-1: Develop models to describe the atomic composition of simple molecules and extended structures.
HS-PS1-1: Use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms.

Answers to Prelab Questions

  1. Complete the following “If/then” hypothesis to explain how the structure of a fabric will influence the relative color intensity produced by a dye.

    “If a fabric contains more ionic and polar dye sites in its structure, then the intensity of the dye color should increase, because more sites will be on the fabric for the dye molecules to bind to.”

  2. Using this hypothesis and the information in the Background section, predict the relative color intensity that will be produced by natural dyes on the six fibers on the multifiber test fabric—wool, acrylic, polyester, nylon, cotton and acetate. Which fibers will produce more intense color? Which will produce less intense color?

    The wool, cotton and nylon with more dye sites will produce the more intense colors and the acrylic, polyester, and acetate will produce less intense colors. Note: Students predictions will vary. In our experience, wool typically had the most affinity for the dyes, with some fresh flowers being the exception (red rose and yellow coreopsis), where cotton had the greatest affinity. Of the synthetic fibers, nylon consistently showed the greatest affinity for the dyes tested.

  3. Sarah wanted to test the effect of concentration of the dye bath on the color intensity. She used one tea bag in 200 mL of water for one test fabric strip and two tea bags in 200 mL of water for the second fabric strip. She allowed both dye baths to come to a boil, and then steep for 15 minutes before removing the tea bags and putting in the fabric strips. She removed the first fabric strip after 15 minutes and left the second fabric strip in the second dye bath overnight. What was wrong with her procedure?

    Sarah kept most of the variables the same, with two exceptions. She changed the concentration of the dye bath and also the amount of time the fabric was left in the dye bath. Any difference in results could be attributed to the concentration, the time, or both. In order to test only the effect of concentration, the amount of time should also have been the same.

  4. Read the entire Procedure and the recommended Safety Precautions. With your group or class as a whole, decide which dye bath and variable you want to test. Write out an action plan for your experiment. See the Background section and Materials list for possible variables.

    Note: Ask to see the students’ plans!

Sample Data

{12701_Data_Table_1}
Note: The vast number of variables prohibits listing all possible results. In general, longer dyeing times and more concentrated dye baths produced more intense colors. Alum had a greater effect with black tea and red cabbage than with herbal tea. Copper(II) nitrate solution produced more green hues and iron(III) chloride produced darker colors and more brown and gray hues. See the Teaching Tips section for more results.

Answers to Questions

  1. Describe the colors produced by the black tea solution. How did the intensity of color on the different fabrics compare to your prediction from Preab Question 2?

    The colors produced ranged from cream to shades of brown and gold. Wool and nylon produced the most intense colors, followed by cotton. The other synthetic fabrics did not take as much of the dye as predicted. Cotton was predicted to take the dye better than it did.

  2. What is the purpose of the control in an experiment?

    The control is used as a comparison in an experiment. When the sample treated with the variable is compared to the control sample (without the variable), the effect of the variable can be observed.

  3. Describe the effect of the variable used in Part B for each type of fabric.

    See Sample Data table. The most noticeable effect was the color change of the wool. The variable showed little, if any, effect on the polyester and acetate.

  4. Compare the general ease of dyeing the six different fibers in the multifiber test fabric. Which fabric(s) consistently developed the most intense colors, regardless of the type of dye or variable used? Which fabric was the most difficult to dye?

    In general, wool produced the most intense color with the teas. The red cabbage dye seemed to have a similar affinity for cotton and wool, but the two fabrics produced very different colors. Wool, nylon, and cotton consistently produced more intense colors than the other three fabrics. Polyester was the most difficult to dye. Acetate did not dye well with the teas, but the red cabbage dye had a greater affinity for acetate than acrylic or polyester.

  5. Suppose you wanted to test the effect of fresh flowers versus dried flowers on the dyeing process. List the variables that would need to be the same for both the control dye bath and the experimental dye bath. What would be the one difference between the two dye baths?

    The two dye baths would need to be exactly the same including concentration, volume, temperature, time of preparation and dyeing time. The fabric used and the container for the dye bath should also be the same. The only difference would be that the control dye bath would contain fresh flowers and the experimental dye bath would have the same amount and type of dried flowers.

References

Historic Native American Natural Dyes from Plants, http://www.museum.state.il.us/muslink/pdfs/dye_plants.pdf (accessed April 2008).

Mihalick, Jennifer E. & Donnelly, Kathleen M., “Cooking Up Colors from Plants, Fabric, and Metal,” Journal of Chemical Education, January 2007, Vol. 84, No. 1.

Student Pages

The Natural Science of Fabric Dyeing

Introduction

Do you have a favorite color you like to wear? With modern synthetic dyes, you can choose from a vast variety of colors. Before the middle of the 19th century, however, the color of fabric dyes was limited to natural sources from plants, animals and minerals. Discover what kind of colors are produced by different plant materials and investigate variables that affect the results—some you may not expect!

Concepts

  • Chemical bonding
  • Experimental design
  • Dyes and dyeing
  • Natural vs. synthetic fabrics

Background

The technique of dyeing fabric is one of the oldest chemical processes developed. Capturing the beauty of plant colors on fabric is an ancient art that was first practiced in Egypt, Persia, China and India more than 5500 years ago. American Indians also made dyes from a variety of plant structures, including petals, roots, stems, leaves and tree bark. Dandelions were used by early American settlers to make dyes of yellow (from the flowers) and magenta (from the roots).

How well a dye is attracted to a piece of cloth (its affinity) depends on both the fabric and the dye molecules. Chemistry thus plays an important role in how and why dyes work. Dyes are water-soluble compounds that are charged. Animal fibers such as wool, which are composed of protein molecules, are usually easier to dye than plant fibers such as cotton, which are composed of cellulose. Wool fibers have many dye sites—groups of molecules that have positive or negative charges and thus attract the charged dye molecules. Dye sites may be ionic, that is, fully charged, or polar, that is, partially charged. In general, dyes have a greater affinity for natural fibers like wool and cotton than for most synthetic fabrics. Many synthetic fabrics, such as acrylic and polyester, are hydrophobic (water-fearing) and have fewer dye sites, making them more difficult to dye. One exception is nylon, the first completely synthetic fiber developed in the 1930s from petrochemicals. Nylon dyes more easily than many other synthetic fabrics because it has polar dye sites. Acetate, another synthetic fiber, is chemically similar to cotton, but has fewer dye sites.

Other than the fabric and dye, many other variables affect the dyeing results. The amount of time the fabric remains in the dye bath as well as the concentration of the dye bath will yield different intensities and hues of color. The discovery of the effect of the container or pot in which the fabric was dyed led to further experimentation. Fabrics dyed in iron pots yield different colors than in copper or aluminum pots. A compound of aluminum, known as alum (aluminum potassium sulfate) is often used to improve the ability of a dye to bond to a fabric, making it more colorfast (less prone to fading). Dye additives like salts of metal ions such as iron, copper, tin and aluminum are known as mordants. The mordant can be used in two different ways—as a fabric pretreatment, by soaking the fabric in a mordant solution before dyeing or by adding the mordant directly to the dye bath.

With the three components of the dyeing process—the dye bath, type of fiber and additives—the variables are almost limitless, resulting in a vast array of beautiful and often surprising colors!

Experiment Overview

The purpose of this activity is to investigate the effect of natural plant dyes on synthetic and natural fabrics using a multifiber test fabric. Students will design and conduct experiments to determine the effects of a selected variable on the dyeing process using either black tea leaves, herbal tea leaves or red cabbage.

Materials

Aluminum potassium sulfate, AlK(SO4)2•12H2O, 1 g†
Copper(II) nitrate solution, Cu(NO3)2, 0.1 M, 10 mL†
Iron(III) chloride, FeCl3•6H2O, 1 g†
Red cabbage extract*
Water, distilled or deionized
Water, tap
Black tea*
Colored pencils (optional)
Herbal tea*
Multifiber test fabric strip, 4 cm
Paper towels
Pencil
Permanent marker
Scissors
Tongs or forceps
Weighing dishes, large, 2
*Dye baths
Additivies (mordants)

Prelab Questions

  1. Complete the following “If/then” hypothesis to explain how the structure of a fabric will influence the relative color intensity produced by a dye. “If a fabric contains more ionic and polar dye sites in its structure, then the intensity of the dye color should (increase/decrease), because____________________________________________________________________.”
  2. Using this hypothesis and the information in the Background section, predict the relative color intensity that will be produced by natural dyes on the six fibers on the multifiber test fabric—wool, acrylic, polyester, nylon, cotton and acetate. Which fibers will produce more intense color? Which will produce less intense color?
    {12701_PreLab_Figure_1_Composition of the multifiber test fabric}
  3. Sarah wanted to test the effect of concentration of the dye bath on the color intensity. She used one tea bag in 200 mL of water for one test fabric strip and two tea bags in 200 mL of water for the second fabric strip. She allowed both dye baths to come to a boil and steep for 15 minutes before removing the tea bags and putting in the fabric strips. She removed the first fabric strip after 15 minutes and left the second fabric strip in the second dye bath overnight. What was wrong with her procedure?
  4. Read the entire Procedure and the recommended Safety Precautions. With your group or class as a whole, decide which dye bath and variable you want to test. Write out an action plan for your experiment. See the Background section and Materials list for possible variables.

Safety Precautions

All food-grade items used in the lab are considered laboratory chemicals and are for lab use only. The dyes will stain skin and clothing. The dye baths are very hot, near boiling. Exercise care to avoid skin burns. Avoid contact of all chemicals with eyes and skin. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines.

Procedure

  1. Cut the multifiber test fabric lengthwise to obtain two 2-cm strips with all six fabrics on each swatch (see Figure 2).
  2. Note that the wool fabric is cream-colored, not white. Use a pencil to mark each wool end with a “W.” Label the strips with your initials or group number as well. Note: Do not use a pen as the ink may “run” when wet.
  3. Label the acetate end of one test strip with a “C” for control (see Figure 2).
    {12701_Procedure_Figure_2}
  4. Obtain two weighing dishes. Using a permanent marker, label each weighing dish with the name of the dye bath to be used. Label one weighing dish “Control” and the other weighing dish with the variable to be tested.
  5. All of the dyes are strong stains. Avoid contact of the dye solution with your skin, clothes, or books. To avoid contamination, rinse tongs or forceps with water before inserting them into a dye bath.
Part A. The Effect of the Type of Fabric on the Dye Process
  1. Observe a multifiber test strip that has already been dyed by the instructor with black tea. On the Fabric Dyeing Worksheet, record the colors produced by black tea (either by description or using colored pencils) for each type of fabric.
Part B. The Effect of ________________________________________________ (Fill in the blank with the chosen variable.)
  1. Add enough distilled water to cover the bottom of one weighing dish. Immerse the test strips into the water until completely wet.
  2. Using tongs or forceps, remove each test strip from the water and allow excess water to drip back into the weighing dish. Note: Twisting or pulling the fabric test strip may result in a separation of the fibers.
  3. Discard the water from the weighing dish and dry the dish with a paper towel.
  4. Immerse the test strip labeled “C” into the dye bath that is the control for the experiment. Note: If pretreatment of the fabric is the variable, do not place the control strip in the dye bath yet. See the note in step 11.
  5. Immerse the second test strip into the experimental dye bath. Note: If pre-treating the fabric with a mordant solution is the variable, first immerse the test strip into the hot mordant solution and allow to simmer for 5–10 minutes. After removing the test strip from the mordant bath, allow the fabric to cool slightly and allow excess liquid to drip back into the bath. Place the pre-treated fabric and the control fabric into the same dye bath at the same time.
  6. After the predetermined amount of time, remove the test strips from the dye bath(s) using tongs. Hold each fabric strip above the dye bath to allow the excess dye solution to drain back into the dye bath.
  7. Pat each test strip with paper towels and then rinse the dyed test strips under running water from the faucet. Continue rinsing each test strip until all of the excess dye has been removed and the rinse water is colorless.
  8. Place the rinsed test strips in the appropriately labeled weighing dishes and allow them to air dry.
  9. When the fabrics are dry, record the dye color produced on each type of fabric for Part B on the worksheet.
Part C. The Effect of ________________________________________________ (Optional)
  1. If another group tested a different dye bath or other variable, record their results for Part C on the worksheet.
  2. Consult your instructor for appropriate disposal procedures.

Student Worksheet PDF

12701_Student1.pdf

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