I think it's the sand or aluminum (harder) media that heats up the body metal and distorts it. The soda, or even plastic, makes less heat. The good thing about soda is you can wash it out of the little crevices, and dry with air, where sand, aluminum & plastic may get stuck in there, and that traps water, making it easy for rust to get a start. The worst part of blasting your car body (or anything not done in a blasting booth) is that you get the media ALL OVER: in your hair, in your shirt, down your pants.. No matter how good you think you shake out your clothes & hair, you still end up bringing it in the house. You might consider going swimming in a pool or a bike ride to get the stuff off you and not bring it home. Maybe you have a buddy that's building himself a garage, so you can borrow it and cover the floor & walls with media, like we did.