Silly string is great fun for Halloween pranks and would-be Spider-Men -- so long as you aren't the poor soul who has to clean it up. Silly string messes are no small job, especially if the stuff has a chance to set. It's so difficult and time consuming to clean that silly string is actually banned in Hollywood during Halloween. Depending on the surface, there are several ways to clean up silly string.
Don't Let It Dry
If possible, always start cleaning silly string while it's still fresh and wet. Once silly string hardens, it becomes a nightmare to remove, adhering stubbornly to most surfaces. Dried-on silly string poses the risk of chipping and peeling paint if removed with too much force, and can leave permanent discoloration and stains on cars and buildings. Wet silly string may smear when wiped, so take care and immediately clean up any residue with water and dish soap.
Power-Washers For The Win
Before and after silly string hardens, a power washer is your best friend for outside messes. High pressure water jets can usually force the gunk off without damaging the affected surface and save you from having to use chemical cleaners and solvents. If you don't have a power washer handy, a high pressure nozzle for your garden hose suffices. Unfortunately, power washers aren't able to help with stains and discoloration.
Soap, Water and Elbow Grease
For interior silly string disasters or getting the fine details after power washing, there's no way around it: It's scrubbing time. Get a bucket of warm or hot water and dish soap, as well as something to scrub everything off with. For hardy, unpainted surfaces like concrete, stiff bristle brushes and other rough tools will do the trick. For more delicate surfaces like cars and painted interiors, use a nylon scrub brush or sturdy sponge. For small cracks and crevices, use a cotton swab.
Clay Bars for Stringed Cars
While car-cleaning soap and a power washer will remove the bulk of the residue from your car, paint contamination requires something a little more drastic. Clay bars can remove some of the contamination and potentially prevent permanent discoloration. Spray car clay lubricant onto the affected area, then cut a small piece of the clay bar and form it into a round flat surface. Slide the bar over the lubricant in a back and forth motion, applying gentle pressure. Once finished, wipe away the lubricant with a microfiber towel. This may not remove all the discoloration, but it can reduce it.
The Unfortunate Truth
The sad fact is that silly string is a ruinous substance that can permanently stain surfaces. If all of your attempts to remove the discoloration have failed, it may be that you have no alternative but to repaint the affected area.