Learn how to make an easy, reusable DIY gel ice pack with a zip top bag and just 3 simple ingredients. ... They’re also more durable, reusable and flexible, so they can mold to fit the body.

Alternatively, the black buildup in ice machines is typically mold growth. Similar to biofilms and bacteria colonies, mold thrives in the damp, dark and undisturbed environment of an ice machine.