Check out our slime recipe below for how to make pumpkin slime quickly and easily. Stop at the grocery store for the ingredients and you have a great Fall STEM activity!


Slime really does make for an excellent chemistry demonstration! Mixtures, substances, polymers, cross-linking, states of matter, elasticity, and viscosity are just a few of the science concepts that can be explored with homemade slime!

What’s the science behind the slime? The borate ions in the slime activators  (sodium borate, borax powder, or boric acid) mix with the PVA (polyvinyl-acetate) glue and form this cool stretchy substance. This is called cross-linking!

The glue is a polymer and is made up of long, repeating, and identical strands or molecules. These molecules flow past one another keeping the glue in a liquid state. Until…

When you add the borate ions to the mixture, it starts to connect these long strands together. They begin to tangle and mix until the substance is less like the liquid you started with and thicker and rubberier like slime! Slime is a polymer.

Picture the difference between wet spaghetti and leftover spaghetti the next day. As the slime forms, the tangled molecule strands are much like the clump of spaghetti!

Is slime a liquid or solid? We call it a Non-newtonian fluid because it’s a little bit of both!


  • Small baking Pumpkin
  • 1/4 Cup Liquid Starch {laundry detergent aisle}
  • 1/2 Cup Clear PVA Washable School Glue
  • 1/2 Cup Water
  • Measuring cup, spoon, and knife {adults only!}


Step 1. Cut the top off the pumpkin.

Step 2. Make room in the pumpkin by loosing up all the seeds and guts. I did take some out to make room but the whole idea is to incorporate the parts of the pumpkin into the slime.

Step 3. Mix 1/2 cup room temp water with 1/2 cup of clear Elmer’s Washable School Glue in a separate bowl. {Other brands of glue do not work as well. You can use white but you won’t see as much of the pumpkin}. Stir to fully incorporate.

Step 4. Measure a 1/4 cup of liquid starch and pour directly into the pumpkin.

Step 5. Pour the glue and water mixture into pumpkin.

Step 6. Get your hands in there and mix. The image below shows all the ingredients in the pumpkin.

SLIME MAKING TIP: We always recommend kneading your slime well after mixing. Kneading the slime really helps to improve it’s consistency. The trick with liquid starch slime is to put a few drops of the liquid starch onto your hands before picking up the slime.

You can knead the slime in the bowl before you pick it up as well. This slime is stretchy but can be stickier. However, keep in mind that although adding more liquid starch reduces the stickiness, it will eventually create a stiffer slime.

Below is the immediate reaction of the glue and starch! It doesn’t take long to make slime!

Enjoy playing with your pumpkin slime! Wash hands thoroughly when you finished playing with your homemade slime recipe. Also make sure to wipe down surfaces thoroughly.

Share your Pumpkin Slime!

Share your projects with us at scsa@edupix.org so we can share it with everyone!

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