If you want to show your students or children a fun experiment that is safe, easy to clean up after completion, and gives really dramatic results, you can create a plastic-like material in minutes with a little milk and vinegar. The experiment is completely safe and you will be able to create whatever you want once the plastic is made.
Steps
Part 1 of 2: Making the "plastic"

Step 1. Gather the necessary supplies
For this experiment you will need 1 cup of milk, 4 tablespoons of white vinegar, a pot or microwave container, cotton cloth or mesh strainer, a bowl, paper towels, and adult supervision. If you want to make more plastic or do this experiment more than once, you will need more milk and vinegar.
- Any type of animal milk will do this, whether it's fat-free, 1% fat, 2% fat, or whole milk.
- You can use an old t-shirt as a cotton fabric.
- You will be working with hot liquid, so it is recommended that children have adult supervision.

Step 2. Heat 1 cup of milk
Measure out 1 cup (250 milliliters or 8 ounces) of milk. You can perform this experiment either by using the microwave or by heating the milk on the stove. If you are going to use the microwave, use a microwave safe container. Pour the milk into a saucepan if you are using the stove. Heat the milk until it is about to boil.
- If you have a sugar thermometer, make sure the temperature is at least 120 ° F (49 ° C).
- Stir the milk continuously if you heat it on the stove.
- Ask an adult to help you with this step.
- To heat the milk in the microwave, run it on 50% of its power for two minutes. After two minutes, continue to microwave the milk in 30-second increments until hot.

Step 3. Add four tablespoons of vinegar to the milk and stir
Add all the vinegar to the container, while the milk is still hot, and stir for about a minute. As you stir, you will notice that some lumps will start to form. If this does not happen, the milk is probably not hot enough for the reaction to occur. Try again with warmer milk.
When hot milk comes in contact with vinegar, the casein protein is removed from the milk. Casein sticks together and forms clots or clots

Step 4. Pour warm milk through the strainer
If you're wearing an old shirt, wrap it around the top of a jar or over a bowl. Put a rubber band there so it doesn't slip. If you are using a mesh strainer, simply place the strainer over the bowl. Let the milk warm up a bit, then pour it over the strainer and let it drain.
As the milk seeps through the strainer, you will see lumps that linger on top

Step 5. Scoop out lumps on paper towels
If you are using a cloth, remove the elastic band and wrap the clots. Squeeze the bag until you remove as much liquid as possible. If you are using a strainer, place the clots on the paper towels using your hands or a tablespoon.
Squeeze the clots onto the paper towel to remove any extra moisture
Part 2 of 2: Molding and Decorating the "Plastic"

Step 1. Gather the necessary supplies
If you want to do something with plastic, you should do it within the first hour while the clots can still mold. You can use cookie cutters, molds, food coloring, glitter, or other decorative materials that you like.
- For better results, you can use sculpting tools.
- You can also use paint and markers once the plastic is completely dry.

Step 2. Knead the casein dough
Before you start, you need to gather all the clots and squeeze them into a mass-shaped substance. Once the clots are in the shape of a lump, knead it well. Work with your hands for a few minutes until it is easy to shape.
Wait for the clots to cool completely before handling them

Step 3. Sculpt the dough using cutters or cookie cutters
Once the dough is well kneaded, you can roll it up and cut out shapes using cookie cutters. You can also press the dough into a mold to shape it. Remove it from the mold and set it aside to dry. Another thing you can do is sculpt the dough any way you want like you would with clay or play dough.
You can add food coloring if you want all the shapes to be the same color, or you can wait for them to dry and paint them later. Add some food coloring to the batter and work until the color is uniform throughout the batter. Gel food coloring works better than liquid food coloring

Step 4. Make plastic jewelry beads
Roll the dough into round beads and poke a hole through the center using a straw. That way, you will get beads that you can insert into a necklace or bracelet. Add glitter while the beads are still wet and it will stick to them as they dry.
Set the beads aside to dry. Check them after a few days to make sure they are completely dry

Step 5. Wait a few days for them to dry
It will take a few days for the plastic to dry completely. If you're not going to do anything else with the plastic, just don't touch it for a few days until it dries. If you molded something, you will need to wait until the plastic dries to use it.
Once it's dry, you can paint or decorate it however you like

Step 6. Paint or color your creations
Color your creations using craft paint or permanent markers as you prefer. You should wait until the plastic is completely dry before adding paint or color with the markers.