Up until recently, I wouldn’t have been able to tell you exactly what my dish sponge is made of. I use them daily to scrub plates, silverware, cutting boards, and reusable water bottles but I didn’t actually know that much about what they’re made of. After doing some research and speaking with experts, I learned that most sponges are made of some form of plastic — probably starting with the prefix “poly,” meaning it’s a synthetic polymer, like polyester, polypropylene, polyurethane and polyethylene.