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At Rosie Riveters we provide hands-on and interactive projects to get girls aged 4-14 excited and engaged in STEM. One project we've wanted to do for AGES but simply haven't had the time during programs (you need at least 24 hours to let them set) is growing crystals! Crystal growing offers a great opportunity to explore suspension, density, and crystallization.  This project is not only fun but you are likely to be able to complete it with materials that you already have at home this Fall. With that in mind, we give you Crystal Cat Pumpkins!
For this experiment you will need the following materials:

Please Note: As both boiling water and Borax are used during this project adult supervision is strongly encouraged. As with any lab environment safety should be your first priority. Avoid direct contact with the eyes and wash your hands after making and handling your crystal cat pumpkins. In case of accidental ingestion, call poison control or seek medical attention.

  • A mini pumpkin  
  • A pipe cleaner (we used white) 
  • A glass container that your pumpkin can fit into and be fully submerged in
  • A plate or similar object that can help to keep your pumpkin submerged and still
  • Borax (3 tablespoons of Borax to 1 cup of water is the normal ration for crystal growing, you will need to adjust based on the size of your pumpkin) 
  • Boiled Water (enough water to support your Borax ratio)
  • Measuring spoon and stirring spoon 
  • Mixing Bowl


  1. Cut your pipe cleaner in half. 
  2. Bend each piece into a "V" shape. 
  3. Place the wire ends of each "V" into the top of the pumpkin to form your cat ears (we added some whiskers too!).  
  4. Set pumpkin aside for future use. 
  5. Measure 9 tablespoons of Borax (more or less depending on the size of you pumpkin or container) into a mixing bowl.
  6. Boil three cups (more or less depending on the size of you pumpkin or container) of water and pour over the Borax. Stir throughly until the Borax is well incorporated into the water.
    • The mixture will appear cloudy as the Borax will not dissolve into the water but instead suspend itself throughout the water. This is called Suspension. In chemistry, a suspension is a mixture of two or more substances. In a suspension, very small pieces of solid are spread through a liquid but do not dissolve. If left still, the solid pieces will separate from the liquid and either fall to the bottom or rise to the top. Sand in water is a suspension. Suspensions may separate quickly or stay suspended for a long time, depending on what they contain.
  7. Place your pumpkin into you glass container. 
  8. Pour the Borax & water over your pumpkin until it is fully submerged. 
  9. You will likely need to use something to help keep your pumpkin submerged in the liquid. We used a plate.
    • Why does the pumpkin float? Because the pumpkin has less molecules than the Borax and water mixture. 
  10. Find a safe place for your pumpkin to sit still in the Borax mixture for 24 hours. 
    • During this 24 hour resting period the Borax mixture will begin to cool causing the suspended solid particles of Borax to begin to settle (fall) onto the surface of the pumpkin and the pipe cleaners and begin to form crystals. The process of crystal forming is called crystallization. Crystals often form in nature when liquids cool and start to harden. Certain molecules in the liquid gather together as they attempt to become stable. They do this in a uniform and repeating pattern that forms the crystal. 
  11. After 24 hours carefully remove your crystal cat pumpkin from the Borax mixture and set gently onto a paper towel to dry. The longer you let it dry the harder your crystals will be. 

We want to thank Little Bins for Little Hands for the inspiration for this project. They have a ton of great experiments you can try out at home. Go check them out. 

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