I have a Foam Helmet, made for climbing. Its kinda old and looks like it needs a wash. The Helmet is old, and so is the foam. Roughly a bit more than 3 years now.
With other foam-made things that are a bit old, I have a personal experience that when I washed them, the foam got screwed, like lost its shape and cushion.
How to effectively wash a foam-helmet and not kill the cushion?
P.S. depending upon the solution provided, I may consider using the same technique to wash my biking helmet.