Make color-changing slime

What can I use if I can't find thermochromic pigment or contact lens solution?

If you can't find thermochromic pigment, substitute thermochromic paint or pigment powder (they still change color) and if you lack contact lens solution use 1/4 teaspoon borax dissolved in 1 tablespoon warm water as the activator for step 8.

My slime is still sticky or won't pull away from the bowl—what should I do?

If the mixture doesn't pull away after adding 1 tablespoon contact lens solution in step 8, add another 1/4 teaspoon of contact lens solution and knead as directed, or add a tiny pinch more baking soda if it's too runny.

How can I adapt this activity for different ages?

For ages 3–5 have an adult wash hands and pre-measure and perform steps 2–9 while the child helps stir and knead, for 6–9 let kids measure with supervision and do step 11 to rub and watch the color change, and for 10+ let them experiment with extra 1/4 teaspoon contact lens solution or different amounts of thermochromic pigment.

How can we make the color-changing slime more fun or unique?

To personalize and extend the activity, stir glitter or foam beads into the glue before adding baking soda (step 5), try layering two slimes with different thermochromic pigments, or use a warm cup and an ice cube to create patterns and record the change to share on DIY.org as in the final step.