Bioplastics (English)

30-60 min

Ages 8+

What Will You Make?

Let’s create plastic milk labels or badges to label or customize!

What Will You Learn?

Homogeneous and heterogeneous mixtures, colloids, as well as separation methods.

Gather your materials...let's get started!

Step 1

Microwave 1 cup of milk for two minutes.

Step 2

Add 4 teaspoons of white vinegar and mix for one minute. The mixture will be a bit lumpy.

Strain mixture

Step 3

Take a strainer to separate the lumps from the liquid. The liquid can be discarded.

Here’s a tip, to get more plastic out of the milk, you can use a coffee filter to strain the lumps of the liquid.

Why is it lumpy? What you are seeing is the milk protein that does not mix well with the acidity of the vinegar, so it separates and accumulates!

Prepare your plastic

Step 4

Put 1-2 drops of food coloring in a small bowl.

Step 5

Transfer the lumps to one of the bowls and mix in the food coloring. If you want, you can also add some sequins or beads!

Knead & Shape your Plastic

Step 6

Place the mixture on a paper towel. Knead the mixture to remove excess water.

Here’s a tip, for best results, knead the mixture until smooth.

Step 7

Once the mixture is shaped into a dough, you can start creating your plastic milk labels. You can punch out shapes with a cookie cutter or just mold the mixture yourself.

Don’t forget to make a hole with a toothpick.

Time to dry

Step 8

Now let them dry, on both sides, the time will depend on the size of your badge. This could take more than 3 hours to completely dry. You’ll know your badges are completely dry if they’re solid and hard.

Paint your plastic with acrylic paint – add a coat of acrylic varnish for a smooth finish!

Finished Bioplastic Samples

What Is Happening Here?

Plastic, Polymers, Milk, Casein

Milk is a heterogeneous mixture, it is considered a colloid. To the naked eye, it seems a homogeneous mixture due to the extreme smallness of its particles, which can be observed under the microscope.

Have you ever heard that milk is full of protein! Well, we separate a protein called casein from the milk, it’s what we turn into plastic. Casein is a polymer, if we look at it closely, the casein molecules look like irregularly curled, wavy balls. The vinegar causes the uneven curls to fan out, stretch, and cling to each other.

What Is Next?

Additional Resources & Experiments

Use your creativity to create more badges or jewelry, with different shapes and colors.

Experiment 1: We used 4 tsp vinegar to 1 cup milk. Would using more or less vinegar affect the amount of casein produced?

Experiment 2: We use vinegar in this activity, but there are lots of other common acids in your kitchen such as: lemon juice, orange juice, soda and tomato juice. Try experimenting making plastic out of one of these acids – do some work better than others?

About MoonMakers

MoonMakers — led by Camila and Diego Luna — are a community of creators passionate about knowledge. A Makerspace, an open space with different digital manufacturing machines. And a YouTube channel where we promote science, technology and the maker movement.

MoonMakers have collaborated with companies such as: Sesame Street, Make Community and in Mexico with Educational Television and Fundación Televisa, creating educational content.

We have given workshops throughout the Mexican Republic with: Talent Land, Secretary of Education in Jalisco, Conacyt, Centro Cultural España.

Materials:

Milk
White vinegar
Measuring cup or spoons
Strainer
Food coloring
small bowls
Paper towel