Make Homemade Silly Putty and Enjoy a Non-Newtonian Fluid
Fun With "Solid Liquids"
Have you ever tried to cut water with scissors, shatter milk without freezing it, or make a snowball out of lemonade? All those ideas sound pretty silly. Everyone knows that you can't cut, shatter, or mold unfrozen, runny liquids...or can you?
If you have played with Silly Putty, you likely know that it can do some pretty weird things. You can cut it with scissors, shatter it with a sharp blow using a hammer, and snap it apart with a swift tug. It doesn't behave like most other liquids. The reason that putty acts so odd is that it is a non-Newtonian fluid.
Here is a recipe to make your own putty. It is very easy and will only take a few minutes to make. After the recipe, you will find more information about the science of putty.
- 1 part liquid starch, available in most stores near the laundry detergent
- 1 part white glue, also known as Elmer's glue, school glue, or PVA glue
- food coloring
- zip top bag
- Pour the liquid starch into the zip bag.
- Add 2-4 drops of food coloring to the liquid starch if you would like your putty to have color. It will be white if you skip this step.
- Add the Elmer's glue to the bag.
- Close the bag and mix everything up by squishing it around.
- One the glue has congealed (it will look like a stringy or well-formed blob) you can remove the putty from the bag.
- If the putty is still like glue and there is little starch left in your bag, add more starch.
- Knead the blob in your hands. It may start out slightly sticky. It will have little form and be slimy when you start. As you knead it and play with it, it will become a well-formed blob.
- Throw out the remaining liquid. Play with your putty. When your putty is not in use store it in an airtight container.
What Is Non-Newtonian Fluid?
A non-Newtonian fluid is a substance that is not a solid and does not follow any of Newton's rules for how a liquid should act. The largest difference between a Newtonian and non-Newtonian liquid is how the substance reacts under an applied force. Most liquids only change viscosity when the temperature changes. An example is water. It acts the same until it is frozen. Once frozen, water is now hard and ridged. Non-Newtonian fluids will change based on how much stress is applied to the fluid.
Try These Activities to See How Your Putty Responds
- Roll your putty into a snake. Hold the snake in two hands and slowly pull your hands apart. Next, do the same thing again but this time quickly jerk your hands apart. What happens? Did the speed change how your putty responded?
- Roll your putty into a ball. Try to bounce the ball on a table. What does it do? If you let your putty sit for a while, what does it do?
- Take a hammer to your putty. What happens? Can you hit it hard enough to make it shatter? Is there a difference in how it responds if you hit it slowly versus quickly?
A Short History of "Silly Putty"
If you buy putty from the store it is a little different from homemade putty. The largest difference is that store-bought putty won't dry out. Store bought putty is a mix of boric acid and silicon oil. It was invented when James Wright of General Electric was trying to find a compound that could replace rubber. For obvious reasons, it didn't replace rubber. Luckily, Peter Hodgson saw some of the failed rubber at a party and saw how people were playing with it. He decided to see if he could sell it as a toy. His solid-liquid was a hit and is still being sold today.