One of the easiest ways to make a substitute for rubber is to mix together household items that form a putty. In fact, Silly Putty was first made as a substitute for rubber during World War II. Silly putty is a polymer made from mixing a silicone oil with a boric acid. You can use cornstarch and water, along with glue to make the putty, but adding vinegar to your solution would cause the putty to become too watery.
Make liquid starch by dissolving 1 tbsp of cornstarch in a little bit of cold water, adding 2 cups of boiling water after the cornstarch has dissolved. If it is too thick, you can add some more water. If you are not going to use the liquid starch right away, store it in your refrigerator.
Place 1/2 cup of white Elmer's glue in a medium sized bowl.
Add the liquid starch slowly in to the glue. While adding the liquid starch, knead the mixture with your hands to thicken it.
Drop in a small amount of food colouring if you want to. If you don't add food colouring, the putty will be white.
Knead the mixture with your hands until it is the consistency you want. If you added food colour, it is best to wear throwaway gloves to keep your hands from getting stained. After kneading for several minutes, the food colouring will no longer stain.
Manipulate the putty slowly in your hands. The putty should be soft and pliable at this point.
Squish the putty between your hands as hard and fast as you can. The texture should now feel more like a rubbery ball than soft putty.
Set the putty on a surface, such as a table, and pound it as hard as you can with your fist. The putty should now feel like hard rubber and won't yield at all.
Put the putty in your freezer to make it stiffer --- don't worry, it won't freeze. To make it more pliable again, you simply have to warm it up a bit.
Experimenting with the consistency of putty may work better with store-bought putty than homemade putty.