You can make your own rubber ball with Borax and glue and other ingredients you might already have around the house. This fun scientific experiment yields a bouncing rubber ball that can be coloured with common food colouring.
Mix 1 tbs. of Borax into 1/2 cup of warm water in a plastic cup. Stir with a craft stick until mostly dissolved. Often some powder remains on the bottom undissolved. This is normal.
Put 3 tsp of plain white glue in another cup. Using a clean stick, stir in 2 to 3 drops of food colouring. Mix well. Try combining drops of different colours for more variety.
Pour the glue mixture into the Borax solution. The glue mixture will begin to thicken immediately. Stir with a stick as long as possible but do not leave in the solution too long. The mixture's consistency will improve as you knead it.
Pick the solidified glue mixture up out of the Borax solution once it is too thick to stir. Knead the solid material with your hands. If the mixture remains too sticky, dip the mass back into the Borax solution briefly and continue to knead until you are able to form a bouncing ball shape.
Store your rubber ball made with Borax and glue in a plastic bag or plastic storage bowl with a lid.
The bouncing ball you formed will bounce and keep its consistency for some time if stored in an airtight container. Length of time before it dries out depends on amount of use and exposure to air.
Borax can burn your eyes so children in particular should wear goggles. Some people are allergic to Borax. Test on small parts of your hand before kneading and wash hands immediately after handling it. Food colouring can stain fabric. Keep the bouncing ball off fabric. Never pour the glue and Borax mixture down drain or clogs will form.