Tarnish and patina on pure copper mugs after a few months of use is to be expected as they are constantly exposed to water and heat every after use or wash. You can easily remove this by following the care instructions which come with your product. Wiping the mugs dry after washing and storing them in a dry place is one way to protect the copper mugs from tarnishing fast. So, proper care and maintenance is a must for copper mugs.Aside from owning artisan hand-crafted mugs, we’re also pleased to let you know that your purchase comes with a lifetime warranty. You can reach out to our customer service team who are always happy to assist you if you have questions and concerns.