Hands-on Activity Let’s Save Our Clothes with Avocados!

Learning Objectives

After this activity, students should be able to:

• Investigate a problem using the engineering design process.
• Explain how dye can be extracted from a natural resource.
• Organize, represent, and interpret data (with the assistance of an adult).

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

State Standards

Materials List

Each group needs:

• 2 unmarked containers with lids to hold avocado dye (must hold a minimum of 3 oz.)
• 6 oz. of avocado dye (see Before the Activity)
• 1 plastic pipette (optional: a pipette could be shared between team members, or you can have one for every team member)
• 1 weigh boat (or other container) for holding the baking soda or vinegar (large enough to hold at least 3 tsp. of those items)
• 1 tsp. measuring tool
• 1-3 tsp. of baking soda or vinegar

For the entire class to share:

• 2 extra unmarked containers to hold 3 oz. of avocado dye for teacher (for modeling)
• 1 extra pipette for teacher (for modeling)
• 1 extra weigh boat for holding 2 tsp. of baking soda or vinegar for teacher (for modeling)
• 1 stained item of clothing (e.g., a white cotton t-shirt with a grass stain). See Troubleshooting Tips for more guidance.
• 3 cups of baking soda (distributed between groups and for use on Day 4)
• 3 cups of white vinegar (distributed between groups and for use on Day 4)
• 1 pan with lid (should hold at least 4 quarts of liquid)
• 1 container to store the excess dye (should hold at least 4 quarts of liquid)
• 1 container (large enough to submerge the stained item of clothing in water)
• stove
• sieve/colander
• optional: containers for transporting or freezing avocado dye if needed
• minimum of 4 peels and pits of avocados, chopped into pieces and washed
• engineering design process anchor chart poster (grade-level appropriate)
• paper towels
• distilled water (or tap water if distilled is unavailable)

Worksheets and Attachments

Pre-Req Knowledge

Students should already have the knowledge about the basics of what matter is and how it can change. The main focus of this activity is to manipulate matter.

Students should already know how to use marked measuring containers and how to use a pipette. However, due to student age and skill set, you are encouraged to assist each group throughout the activity as needed.

Students should already know what dyes are (e.g., such as those used in cupcakes, tie dyes, hair dye, etc.); that way it’s easier for them to understand what natural dyes are.

Students should be familiar with the engineering design process steps at their grade level.

Students should already be familiar with the definitions of reduce, reuse, recycle, and pollution.

Introduction/Motivation

Today we will review, reduce, reuse, recycle. (Show stock images of landfills.) When we put things in the trash, this is where they end up, and they can be there for years and years, creating pollution for our planet. (Alternatively, you can show a read aloud of “Fly Guy Presents: Garbage and Recycling” by Tedd Arnold [11:37 minutes].)

But there are ways we can help decrease the trash that goes into landfills. You already know about reduce, reuse, and recycle, so we will talk more about reusing items! For example, did you know you can change the color of clothes? We can change the color using chemicals that pollute the environment, or we can use natural items!

Today we will begin an experiment that we’ll work on for several days. Our main question for our experiment will be: ”How can we reduce the amount of clothing that goes into landfills by using dye from natural resources?” (Optional: Write the question on the front board of the classroom.)

Procedure

Background  

pH plays an important role in our food, from making lemons acidic and limes sour, to making acid-base reactions in baking that make cakes fluffy. Using the pH scale, we can quantify how acidic or basic something is with a number. Some compounds have distinct color changes in response to changes in pH; we call these pH indicators. They can be used to create a color change that shows when a solution changes from acidic to basic. 

Anthocyanins are water-soluble pigments naturally found in red, purple, and blue fruits and vegetables (e.g., blueberries, grapes, red cabbage). These pigments can be isolated and used as a natural food colorant. Upon changes in pH, the color and stability of anthocyanins begin to change, making it a good pH indicator. In acidic conditions, anthocyanins appear red, and they are more blue in basic conditions. These are the reasons why using baking soda and vinegar in this activity will change the color of the avocado-extracted dye. In this case, the avocado will not be changing color drastically, since the activity uses safer chemicals, but the dye will get darker or lighter, and you will notice a change in color. The activity uses avocado as our source because of its bonding properties to natural fibers; for other foods, such as red cabbage, dye will wash off from clothing. It is important to use fabric that is natural (cotton, silk, bamboo, etc.) in order for the dye to bond properly and withstand washing.

Before the Activity

• Gather materials and make copies of the Pre/Post-Quiz, Procedure How-To Sheet, and Properties of Matter Observation Booklet.
• Post the engineering design chart anchor poster in a visible area of the room.
• Search for and prepare to show a few stock images of landfills to introduce the activity (e.g., from iStock or Wikimedia Commons).
• Optional: Pre-treat/mordant your stained article of clothing before Day 4 to increase your chances of keeping the dye adhered to the fabric.
• If you choose to pre-treat your fabric, this should be done prior to dying the fabric. Please follow proper safety protocols if you choose to use any harsh chemicals, which includes not having students access them.
• Pre-treating options:
• Pre-treating can be done with a pH-neutral solvent such as Synthrapol, which can be purchased from Amazon (you can also use pH-neutral detergents). That method is often used for tie-dying projects.
• You can also use more natural solutions such as soy milk, although it’s a bit longer of a process to pre-treat. If you’d like to take this optional step of pre-treatment, there are YouTube tutorials on mordanting fabric (e.g., this 7:48-minute video, “Natural Dye Basics: Mordanting”) or books about the subject (e.g., Rebecca Desnos is a great source).
• If you have time/school constraints on the use of a stove, you can extract the dye from avocados at home prior to Day 1. Please note: It is highly recommended to do this no more than 1-4 days before you are going to use your dye, as the dye may begin to grow bacteria over time.
• Materials needed: 1 pan with lid, stove, sieve/colander, minimum of 4 peels and pits of avocados, chopped into pieces and washed
• View the video tutorial (7:39 minutes) and/or read through this how-to guide for detailed instructions on how to pre-treat your fabric (optional) and extract the dye.
• Make at least 4 quarts of dye. Store the dye (in a refrigerator or freezer) for use on Days 3 and 4 of the activity.
• Make a video of the process to show to students, or prepare to show the YouTube video tutorial (7:39 minutes).
• Before Day 3:
• Fill up containers for students and for your demonstration with 3 oz. of avocado dye.
• Set out materials for your demonstration and separate out materials that will be passed out to groups. The demonstration and each group will need:
• 2 unmarked containers with a minimum of 3 oz. of avocado dye in each
• 1 plastic pipette (optional: 1 pipette for each group member)
• 1 weigh boat with 1-3 tsp. of the group’s chosen substance
• 1 tsp. measuring tool

During the Activity

Day 1:

Objective: Background on Landfills.

1. Hook students by using information in the Introduction and Motivation section.
2. Briefly review the basics of states of matter, how they can change, and how we can describe these changes.
3. Be sure to point to the engineering design process anchor charts to remind them that we will be following most of the steps during our unit. Point out that learning about landfills and determining the main question for the experiment are part of the “Ask” step of the engineering design process.
4. Tell them we are going to be learning about how to save a garment from going into a landfill by using natural dye. We will also be changing its properties!
5. Administer the Pre/Post-Quiz.

Optional Extra Day:

Extract the Avocado Dye as a Class:

1. On this day, you will extract 4 quarts of dye from avocados.
2. Ensure that the materials are on hand: 1 pan with lid, stove, sieve/colander, and a minimum of 4 peels and pits of avocados, chopped into pieces and washed.
3. Have students predict what color the dye will be based on what they observe about the avocado peels and pits.
4. Follow directions from the video tutorial (7:39 minutes) and/or read through this how-to guide for detailed instructions on how to extract the dye (see Figure 1). Clearly state each step to students as they observe the dye extraction process.

   

5. You may not be able to complete the entire process in class because of how long it can take the water to simmer. Inform students that you will carefully store the dye in the refrigerator (or freezer), and it will be ready to use for Days 3 and 4 of the activity.   

Day 2:

Objective: Students Design Experiment

1. If you did not extract the dye as a class during the Optional Extra Day: Show a video of the avocado dye extraction process to demonstrate how we got the dye. Use a video of your making, or this YouTube video (7:39 minutes). If using the YouTube video, you can skip ahead to show only the extraction portion, or you can show the entire video, which outlines a lot of fun information that the students may find fascinating.
2. Tell the students how we will be using avocado dye that’s been made just like the video. We will be changing its properties (the color) by using either vinegar or baking soda—their choice. These substances have properties that react with the dye, which in turn will make our dye change color. Changing the properties of the dye is part of an “experiment” to test our solution to save a garment from going to the landfill. Engineers always test their solutions to problems to see if they work and how they can be improved.
3. State that today there are two major objectives to complete as a group: 1) decide whether the team is going to use vinegar or baking soda, and 2) decide how many scoops of that substance they think they will need to make the color of their dye change.
4. Show the 1 tsp. measuring spoon to demonstrate how they will measure out their scoops. Give them the option of choosing 1, 2, or 3 scoops in order to limit extreme changes/errors in the final product.
5. Pass out the Procedure How-To Sheet for their plan.
6. Have the students verbally plan out with their team how they will perform their experiment, and then sketch and write out their design for how to change the color of their avocado dye. Tell them that this serves as the “Imagine” step for their experiment.
7. Finally, have the students complete their Procedure How-To Sheet by writing out the steps they will take tomorrow. Tell them this serves as the “Plan” step for their experiment.

Day 3

Objective: Changing Color/Properties

1. Tell students that today we will be changing the color/property of our avocado dye by following their designs from yesterday.
2. Explain each item they will be receiving and mention how they will be getting two containers of the avocado dye because one is to be left unchanged in order to compare their experiment changes to it. Each group will receive the following:

• 2 unmarked containers with a minimum of 3 oz. of avocado dye in each (Make sure to stress that one is being left alone, and have them place it at the very front of their table as a reminder.)
• 1 plastic pipette (optional: 1 pipette for each group member)
• 1 weigh boat with 1-3 tsp. of the group’s chosen substance
• 1 tsp. measuring tool
• Properties of Matter Observation Booklet

3. Explicitly model how they will be using their materials and how exactly they will be adding the scoops of their substance into one of the dye containers.

1. Display the same items the students will have.
2. Move one of the dye containers to the front of the table as a reminder not to use that one.
3. Pretend to use the tsp. measuring spoon to scoop vinegar or baking soda from weigh boat, and then pretend to pour it into the second container.
4. Shake it and pretend to observe changes.
5. Pretend to add another scoop of a substance, shake it, and then pretend to observe changes.
6. Model one more time, depending on class needs. If the class needs additional support, provide a visual on a dry erase board/poster in front of the class.

4. Have students verbally make predictions with their team about what they think will happen during the experiment.
5. Pass out items to groups.
6. Have students fill out the “Before” section of the Properties of Matter Observation Booklet by observing the properties of their dye. Do not let students taste the dye. Instead, have them imagine what the dye might taste like from its look and smell.
7. Have students carry out their design from Day 2 using one of the avocado dyes. Monitor students as they work, and provide assistance as needed.
8. Finally, have students fill out the “After” side of the Properties of Matter Observation Booklet. Do not let students taste the dye. Again, have them imagine what the dye might taste like from its look and smell.
9. Have every team discuss their findings within their team and then share their findings with the class. Ask students if their predictions were correct. Example questions for the class discussion: Were the number of scoops your group chose correct, or did your dye color change with less of that amount? What would you change if you were to repeat this experiment? What do you think went well? What do you think did not go well? 

   

Day 4

Objective: Saving a Piece of Clothing by Dying It

1. Have students predict whether the clothing item can be saved by the dye or whether it needs to be trashed. Encourage students to write down their predictions on a piece of paper, or write student predictions on the board.
2. Add the remaining avocado dye (from the 4 quarts originally made) to a pan.
3. As a class, vote on changing the dye by adding vinegar or baking soda. Remind students to think about their observations from Day 3 and how adding vinegar or baking soda might change the results of dyeing the stained garment.
4. Add the remaining vinegar or baking soda to the dye and stir.
5. Soak the garment in distilled water (or tap water) and ring out the excess water. Optional: Have a student volunteer help to soak the clothing.
6. Add the garment to the pot of dye.
7. Let soak overnight. No heat is necessary, but it is optional if you want to increase your chances of dye adhesion even further.

Day 5

1. Remove the garment from the pot of dye and ring out the excess water.
2. Let the garment air dry under shade (direct sunlight will affect the color).
3. As a class, examine the completed dyed garment and discuss the results. Example questions for discussion (student answers may vary): Can you explain what happened to our garment? What went well? What would you do differently? Is there another way you can think of saving a garment? Will you be using this method to naturally dye something at home with your family? Do you have other ideas about how to save garments from landfills safely?

Vocabulary/Definitions

dye: A substance that is used to give color.

extract: To remove via a chemical process.

garment: An article of clothing.

substance: A pure form of matter that only contains one type of atom.

Assessment

Pre-Activity Assessment

Have students complete the Pre/Post-Quiz. They should list a solution that would prevent a garment from being thrown out and sort a group of words that can be classified using the following senses: sight, taste, touch, and smell.

Activity Embedded (Formative) Assessment

Have students create a dye solution to repair an example of stained clothing. Have them write their repair method on the Procedure How-To Sheet and predict whether the clothing item can be saved or needs to be trashed.

Post-Activity (Summative) Assessment

Administer the same Pre/Post-Quiz and have students reflect on their original responses.

Have students revisit their predictions about whether the stained article of clothing can be saved. If students originally chose to trash the clothing item, have them elaborate on how to use the avocado method to save the item. If students predicted that the clothing item could be saved, have them elaborate on why the avocado method worked to save the item. (Example answer: The avocado method saves the item, because then it can be reused instead of going to a landfill just because it had a stain.)

Safety Issues

Extraction of avocado dye:

• The avocado dye can be safely extracted with the class if you have a school stove and your school allows it, but this will add an extra day to the activity. Follow your school’s safety precautions should you choose this option. If you choose to cut the avocado pits into smaller pieces, use care when handling the knife.
• The exact amount of dye needed may vary. It is recommended to make at least 4 quarts of dye in order to have enough for Days 3 and 4 of the activity. Check the amount of dye needed by measuring out exactly how much water covers your garment by adding your garment to a pot, covering it completely with water, weighing it down with something that can handle heat, and then adding even more water to account for evaporation during the heating process. Alternatively, you can create more dye after the first time using the same avocado pits/skins you used. The pits/skins also freeze very well; just be sure to completely clean them of food particles to avoid mold.
• The avocado dye can be stored safely in the fridge for up to a week without growing bacteria/mold, or it can be frozen for up to approximately 4 months. If freezing dye, be aware that you will need to take into account thawing time and starting color differences due to the additional water in your dye from the freezing.

During the Day 3 activity: Due to age/student needs, it may be helpful to have another adult there to help pass out the supplies and ensure that safety precautions are taken. If that is not possible, and safety/time is a concern, you can have the class work on an independent activity while calling on one group at a time to conduct their experiment.

Avocado dye itself is very natural, and therefore safe, but because of germs, students should not consume the dye or any of the ingredients. Do not let students taste the dye. Instead, have them imagine what the dye might taste like using their observations of its look and smell.

Please remember that the avocado dye will NOT adhere to the fabric forever, unless it’s prepared. For the purposes of this activity, it is optional to pretreat the fabric to withstand washing, but if you would like to extend this activity by dying clothes/fabric for your class for long-term use, be sure to research mordanting ahead of time.

Troubleshooting Tips

For the best results, the stained article of clothing should be white and made of at least 90% natural materials (e.g., cotton, linen, silk, bamboo, wool, etc.).

Activity Extensions

In order to extend the activity, you can use the same avocado peels/pits to extract more dye, which then can be used to dye watercolor paper (or print paper), essentially creating your own cute stationary for letter writing. This can go along well with English Language Acquisition / Spanish Language Arts and Reading (ELA/SLAR) writing units.

Activity Scaling

You can scale this lesson up by teaching about the pH scale, acids, bases, and why exactly the vinegar and baking soda are creating a change in the avocado dye color. You can also have additional opportunities for students to explore other safe acids and bases and then add these item images onto a student-friendly pH scale based on their properties. Examples include tomato juice, egg, water, and kale.

Copyright

Contributors

Supporting Program

Acknowledgements

This curriculum was developed under National Science Foundation RET grant no. DMR-1720595— Center for Dynamics and Control of Materials at the University of Texas at Austin. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.