Silly String is a popular children's toy consisting of a polymer-based resin canned with a propellant. Adult celebrants and pranksters are also fond of the product, which is often used at parties, parades, celebrations and on holidays such as Halloween. While Silly String is notoriously hard to get off most surfaces, there are several ways to remove it from car paint without damaging the finish.
Remove as much of the silly string as possible by washing your car with a garden hose or power washer. Use water first to remove as many of the chunks as possible, then dry the car.
Go over small areas such as door seals, car mirrors and around the car's lights with a cotton swab, using the swab to lever as much of the silly string as possible out of the intricate areas.
If your car paint still shows Silly String residue, test your solvent on an inconspicuous area such as the inside of a door. If the solvent has no adverse effects on the paint, spread it over one area of Silly String residue and allow it to sit for a few minutes. Buff away with a chamois or cloth. Repeat for any other areas of residue.
If the solvent does not remove all the residue, apply clay lubricant to the remaining patches. Then go over the area with a clay bar, which is formulated specifically to remove stubborn residue from car paint. It might take several applications to remove the rest of the Silly String.
If even the clay bar does not remove the Silly String, see a professional auto detailer or body shop. Because Silly String is a polymer, it might contaminate some car paints down to the primer coat, necessitating a professional repainting.
