Sources suggest that you may use a car part lubricant.
Here's how to remove silly putty from rubber shared by Hunker.com.
Step 1:
Remove as much of the Silly Putty as possible from the rubber surface. If you don't think the rubber will be harmed, use the blunt end of a dinner knife to scrape the putty away. There are many Silly Putty clones sold under other brand or store names. The basic properties are the same; even if another brand name of putty is adhered to the rubber surface, the same cleaning techniques are effective.
Step 2:
Spray the Silly Putty and rubber around the putty remnants with a car part lubricant. Wait about three minutes for the lubricant to work under the putty. According to Crayola, as endorsed by the Silly Putty brand, use a cleaning cloth to wipe away the putty remnants.
Step 3:
Soak cotton balls in rubbing alcohol and scrub any remaining Silly Putty stuck to the rubber and/or the rubber surface in a back-and-forth motion.
Step 4:
Apply liquid dish detergent to a damp sponge and clean the car part lubricant and alcohol residue from the rubber surface. Because of the silicone compounds in the Silly Putty, the putty clings to rubber and plastics more than other products. According to the official Silly Putty website, the combination of silicone oil and boric acid creates what is referred to as a solid liquid, which allows the product to bounce, stretch and be molded.
Silly Putty is one of the top-selling children’s toys of all time. However, the ooey-gooey substance isn’t just for kids. Here are 15 facts about Silly Putty that prove it’s a true product of American ingenuity—not just a petty plaything from Mentalfloss.com.