It looks legit and realistic, plus, it fits the theme so well.
Check this video tutorial out byMake Life Lovelyon YouTube to learn how.
If the cauldron you bought is not black, then spray paint it black, and let dry completely.

Image credit: Make Life Lovely via YouTube
Once the paint has dried, lightly spray them with white for a charred look.
Easy DIY Fake Fire & Witch Cauldron For Halloween

