What can you do to make rubber shrink?

Yes, rubber can shrink, in two ways, for two separate reasons.

Rubber can shrink if put in the dryer for an immense amount of time, the reason for this is the molecules in the rubber absorb the nucleotides around the surface, there for, giving the rubber a smaller appearance.

Rubber can also shrink if you leave it in the sunlight for too long. Now this is a debated subject, but it is very true. The rubber absorbs the leftover photons the sun contributes to the objects and organisms around it, therefore, making the rubber shrink.

The way you can get rubber, depending on the type, to be prevent from shrinking, you can either rub saliva on it, making the rubber absorb the bacteria and create antibodies against the dryer nucleotides and photons from the sun. Another way is not leaving your rubber in the dryer or the sun.