Puffy Paint in the Microwave
Sick Science! Summer Camp - It's art, it's food, it's science!
This demonstration only uses a few kitchen items and requires very little set up and clean up time. It’s perfect for little scientist-artists who are always looking for new activities and wondering how they work.
- Small bowls
- Mixing spoons
- 1 tablespoon self-rising flour
- 4 Drops of food coloring
- 1 tablespoon of salt
- Paint brushes or cotton swabs
Combine the 1 TBSP self-rising flour, 1 TBSP salt, a few drops of food coloring, and enough water to make a paste.
Mix until combined. The mixture should be pasty and will not be smooth.
Use cotton swabs as paint brushes and paint a picture. You can also use your fingers to paint. Just make sure you get a thick coating. Thin strokes may not have enough flour and salt to puff up.
Microwave for 10-30 seconds.
WARNING: Watch the paint in the microwave. Cardboard can start to burn if left in too long. Plus, it’s fun to watch the paint bubble and puff while it cooks.
Let the paint dry completely. When dry, the paint will be hard and will stay puffy.
How Does It Work
The key to this activity is the self-rising flour because it contains baking powder and a little salt. The baking powder is important because it is a leavening agent – an ingredient added to pastries, bread and bakery to produce carbon dioxide and make them rise. It is also known as the chemical sodium bicarbonate. Baking power is made from sodium bicarbonate, an acidifying agent, cream of tartar, and a drying agent like starch.
When the baking powder is mixed with water, it releases a carbon dioxide gas. The cream of tartar in the baking powder is an acid that also reacts with the sodium bicarbonate in water. Add the extra salt, which also reacts with the chemicals in the baking powder to release even more CO2, and you have the makings for a bubbling paint potion.
The heat plus the water in the microwave will cause the baking powder to release small amounts of CO2, producing even bigger bubbles. It’s important that you use a thicker paper that can not only support the weight of the puffy paint, but also hold up for a few seconds in the microwave.
This is the same reaction that takes place when you bake a cake. The heat in the oven, mixed with the water and baking powder releases the carbon dioxide gas, producing bubbles. The bubbles try to rise and make their way to the surface, making the entire mixture rise. Not all of the carbon dioxide bubbles escape, because the heat begins to make the cake solid. Once the cake is finished cooking, the carbon dioxide slowly leaves. If you look at the top of bread or cake, you can see where the tiny bubbles left the mixture and popped. This is also why bread and cakes are fluffy and soft – they are filled with tiny air holes.
The starch is added to baking powder to keep it dry and prevent an explosive reaction from happening in the can.
All-purpose flour is a blend of hard and soft wheat only. If you use all-purpose flour, you will need to add baking power and extra salt to your paint to make it bubble.
Self-rising flour is usually lower in protein than other types of flours. Foods made with self-rising flour are usually lighter, fluffier and crumbly. So before you start baking, consider your ingredients and plan out your outcome. Some breads will not turn out as well with the self-rising flour. If you do use self-rising flour in a recipe, make sure to omit the baking powder so you don’t have an out of control bakery that rises more than it should while cooking. Baking powder deteriorates with age, so don’t keep it for a long time or buy a lot at one time unless you plan to use it in the near future.
Science Fair Connection
While creating puffy paint from kitchen ingredients fun, it isn’t a science fair project. You can create a science fair project by identifying a variable, or something that changes, in this experiment. Let’s take a look at some of the variable options that might work:
- Test different types of flour such as self-rising, all-purpose, bread, buckwheat, organic, instant, rice, gluten, etc. Which one will rise the best? You can even make your own self-rising flour by adding baking soda, cream of tartar and salt to all-purpose flour.
- Test the shelf life of flour and baking powder. What happens when you use year old flour vs. fresh? Year old baking powder vs. fresh?
- Test different amounts of salt. How does this affect the paint mixture?
These are just a couple of ideas, but you aren’t limited to them! Come up with different ideas of variables to test and give them a try. Remember, you can only change one variable at a time for each test. For example, if you are testing different types of flour, make sure that all other factors in the test remain the same!
Ask an adult to supervise while microwaving the paint and carefully watch it in the microwave. Cardboard can start to burn if left in too long.