How to Make Slime {Polymer Play}

After the utter joy of bouncy ball making, I thought probably slime would be a hit also. So this week I showed the girls how to make slime.

Discover More! Read how we created a special science nook for our preschoolers

Slime is a gooey, sticky, non-Newtonian fluid that is typically made by mixing a polymer like glue with an activator like borax. It can be stretched and molded but also oozes slowly, behaving as a substance between a liquid and a solid. Slime is popular as a sensory toy and can be customized with colors, glitter, or other additives.

What is Slime and its Properties?

• Non-Newtonian fluid: Its viscosity (thickness) changes depending on the force applied to it. When left still, it acts like a liquid, but when squeezed or pulled quickly, it feels firm. 
• Made from a chemical reaction: The characteristic texture of slime is a result of a chemical reaction between a polymer in the glue and the borate ions from the activator, which causes the polymer chains to link together. 
• Can be made in many ways: While the traditional recipe is PVA glue and borax, many variations exist using other ingredients like contact lens solution, baking soda, shampoo, or cornstarch to change the consistency, color, and other properties. 

Popular Uses and Variations

• Sensory toy: Its unique texture is a major reason for its popularity, as it’s fun to squish, stretch, and mold. 
• DIY and craft projects: Slime is a popular DIY project where users can experiment with different colors, scents, and textures. 
• Variations: Popular types include fluffy (made with shaving cream), glitter, and glow-in-the-dark slime. 

Making slime requires just a few ingredients: a polymer (like PVA glue) and a cross-linking agent, or activator. The recipe can be customised with colour, glitter, and other add-ins. Here are two popular recipes for making slime, including a safe, borax-free option. 

Method 1: Borax slime 

This classic recipe is simple and creates a bouncy, moldable slime. 

Ingredients 

• 1 tsp borax powder
• 1 1/2 cups water, divided
• 4 oz (about ½ cup) of PVA glue, like Elmer’s
• Food coloring (optional) 

Instructions 

1. Prepare the borax solution: In a large bowl, dissolve 1 teaspoon of borax powder into 1 cup of warm water and stir until completely dissolved. Set this aside.
2. Mix the glue base: In a separate medium-sized mixing bowl, combine the glue and the remaining ½ cup of water. Add a few drops of food coloring and stir until the color is consistent.
3. Combine mixtures: Slowly pour the borax solution into the glue mixture while stirring. You will see the slime start to form immediately.
4. Knead the slime: Stir the mixture until it becomes too hard to mix with a spoon, then use your hands to knead it. Continue kneading until the slime firms up and is no longer sticky. Discard any excess liquid in the bowl.
5. Store it: For later use, keep the slime in a sealed plastic bag or airtight container. 

Important safety note: Borax should not be ingested or come in contact with the eyes. Do not make this recipe with young children who may put their fingers in their mouths during play. 

Method 2: Saline solution and baking soda slime 

This borax-free recipe uses a baking soda and saline solution activator, making it a popular choice for young children. 

Ingredients 

• 4–6 oz washable school glue
• ½ tsp baking soda
• 1 1/2 tbsp multipurpose contact lens solution (must contain boric acid)
• Food coloring and glitter (optional) 

Instructions 

1. Combine glue and baking soda: Pour the glue into a bowl and mix in the baking soda until thoroughly combined.
2. Add color and glitter: If you want colored or sparkly slime, add a few drops of food coloring and a pinch of glitter at this step. Mix well.
3. Mix in saline solution: Add 1 1/2 tablespoons of contact lens solution to the mixture and stir slowly. The slime will begin to come together, pulling away from the sides of the bowl.
4. Knead the slime: Take the slime out and knead it with your hands until it becomes smooth and less sticky. If it’s still too sticky, add another small amount of contact lens solution and knead again.
5. Store it: Keep your slime in an airtight container to prevent it from drying out. 

Safety considerations

• Chemical burns: The recipe which uses Borax, can cause chemical burns if used improperly or carelessly. 
• Proper use: It’s important to play with slime in a safe area and wash your hands thoroughly after playing with it.

After they had finished I gathered it all into a Ziplock bag and popped it in the fridge for their discovery time later on in the week.  I’ll be posting about that tomorrow.