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Can You Harden Silly Putty?

You cannot harden Silly Putty. You can dry it out if you heat it in the oven, and while this hardens your Silly Putty, it also makes it brittle. However, you can stiffen homemade Silly Putty if it is too runny.

Are you a fan of how easy Silly Putty is to make at home but prefer a harder consistency? This article will help you understand whether you can harden your Silly Putty and answer some other questions you may have about this material. To learn more, keep reading.

You Cannot Harden Silly Putty

Silly Putty has a soft, squishy consistency. It’s a material that can bounce when dropped and flow like a liquid. If you hit it hard enough, it can even break apart. 

However, it cannot be hardened. 

Silly Putty is designed to be flexible, and hardening it defeats this purpose. You can stiffen it, and there are two ways to do so:

  • Leave it out of the container uncovered. Homemade Silly Putty will likely dry out within a few days to a few weeks, but it can take years for store-bought Silly Putty to dry out.
  • Bake it. Keep the oven low to moderate temperature and bake your Silly Putty. This draws out all the moisture, drying it out.

However, Silly Putty doesn’t become hard so much as it becomes brittle and easily breakable when dried out. At this point, it stops being fun to play with.

You could conceivably use your Silly Putty to create a sculpture and then bake and store it. However, it would still be brittle and easily breakable. Additionally, there are better options than using Silly Putty for models, such as modeling clay. 

However, Silly Putty is a good option if you’re looking for a way to practice sculpture – it’s a low-risk medium, and you don’t have to worry about losing out on expensive material if you make a mistake when trying out new shapes and designs.

You Can Stiffen Homemade Silly Putty

Occasionally, when people talk about “hardening” Silly Putty, they are actually looking for ways to stiffen homemade Silly Putty. If your homemade putty is too runny, you’re in luck – it is possible to fix this issue.

The best way to stiffen your Silly Putty is to add cornstarch to the liquid mixture. Add in one tablespoon (8 g), knead it into your Silly Putty, and repeat until you’re satisfied with the consistency. 

You can also fix Silly Putty that is too crumbly or has dried out. How to do so depends on what type of Silly Putty it is:

  • If it is homemade Silly Putty, add soap or hair gel to the putty one tablespoon (14.8 ml) at a time. Knead it in and repeat until you’re satisfied with the stretchiness of the putty. 
  • If it is store-bought Silly Putty, it already has all the liquid it needs. Instead, you simply need to knead it and continue kneading until the putty softens up again. However, you will be unable to soften expired Silly Putty that has also dried out, so if your putty isn’t softening up, check the date.

Ingredients for Making Homemade Silly Putty

Whether you plan to play with your Silly Putty or need something to practice your modeling skills with, homemade Silly Putty is your best bet. While you won’t get an exact match for store-bought Silly Putty, it’s significantly cheaper, and you can make it with ingredients you probably already have at home. 

To make homemade Silly Putty, you will need cornstarch, clear liquid soap, and (optionally) food coloring and glitter. You will need about two parts of cornstarch for every 1 part of liquid soap.

Once you’ve got your ingredients, you should:

  1. Add both the cornstarch and soap to a bowl and mix. At this stage, your Silly Putty should be clear.
  2. Squeeze a few drops of food coloring (in your preferred color) into the mixture. You can also add some glitter to make your Silly Putty shiny if desired.
  3. Combine the ingredients together with your hands. Keep kneading the mixture until your Silly Putty comes together.
  4. If the texture isn’t coming out right, add more soap (to soften it) or cornstarch (to stiffen it). As mentioned above, add one tablespoon (8 g) at a time until your Silly Putty is right.

Store your Silly Putty in an airlocked container or zip-top bag.

Final Thoughts

You cannot harden your Silly Putty – Silly Putty is designed to be soft and flexible. If you dry out your Silly Putty, it will become hard, but it will also become brittle and break very easily.

For more, check out What Is the Best Paper for Paper Airplanes? (That Fly Far).