EASY TO CLEAN - This vessel is Design copper and will naturally discolour, tarnish and develop black spots with use. It can easily be cleaned in minutes. Please read the cleaning, use and Washing instructions before use. Clean your bottle regularly - To restore the inside is 2 TBSP of concentrated lemon juice, 1 TBSP of sea salt or normal salt, 1 cup of water, shake for 2 minutes, give any stubborn areas a scrub with a dish/bottle brush and flush clean with cold water, ensuring all applied things residue is washed away.