Copper drinking mugs are making a comeback in kitchens, dining room, and bars across North America. This classic drinkware is both functional and practical and just the right amount of vintage. It not only keeps beverages—like your favorite type of Mule—crisp and cold for longer, but it’s also a unique design that’s sure to make a stylish statement when on display in any home or business.

Once you decide to take the plunge to buy your own personal set of copper drinking mugs (and you won’t regret it, trust us), there are a few things you need to know. Like most beautiful and beloved kitchen items, copper drinking mugs need some TLC to look their best. We’ve compiled a list of the sins of copper mug care. To ensure your copper mugs shine with the same rich gold-like tone as the day you bought them, here are a few things you definitely should NOT do.

Don’t Do This to Your Copper Drinking Mugs

1. DON’T Put Them in the Dishwasher

Copper drinking mugs are NOT dishwasher safe. Please don’t put them in the dishwasher. You wouldn’t put your crystal wine glasses in the dishwasher, right? Dishwashers are too rough for copper mugs and other fragile or more expensive dishware. They accelerate copper corrosion and weaken the tin or stainless steel lining, if your mug is lined. This can cause copper to leak into your next beverage as well as result in unsightly cracks or flakes.

2. DON’T Let Them Sit Around While Wet

Whether it’s vodka remnants leftover from your cocktail or residual water from washing your copper mug, liquids should not be allowed to linger on your copper mug for too long. Moisture—especially on the outside of the mug—causes oxidation, which soon leads to the development of a patina.

3. DON’T Store Them in an Enclosed Space

Enclosed spaces like dark, dank cupboards are no place for copper drinking mugs. Moisture often collects on mugs in enclosed spaces, since it has no way to escape. This build up of moisture will cause that ugly patina to form much earlier than you’d like to see it.

4. DON’T Fill Them with Hot Beverages

Hot and acidic beverages break down the copper in your mug, which could turn your copper mug into a health hazard. When the copper on unlined copper mugs starts to dissolve, it may leak into your beverages. While copper is safe to ingest in small quantities, it can cause health problems if you drink too much.

Do This Instead—The Right Way to Care for Your Copper Mugs

1. DO Wash Them by Hand

Like other valuable dishware—antiques, real silverware, crystal wine glasses—copper drinking mugs need to be washed by hand—and gently. Wash them immediately after use so that any remaining residues are easy to remove. Regular dish soap and warm water will work wonders, just make sure you don’t use an abrasive sponge or scrub too hard.

2. DO Dry Them Right Away

To avoid the development of that dreaded patina, dry your copper mugs right away after washing them with a soft dishtowel. Be gentle! While some people like the antique patina look, it does indicate that your copper mugs have sustained damage, and definitely shortens their shelf life significantly.

3. DO Fill Them with Cold Beverages

Copper drinking mugs were designed to keep chilly, refreshing beverages colder for longer. Instead of ruining your copper mugs by filling them with hot drinks, use them as intended: for icy cold cocktails like your favorite Moscow Mule.

4. DO Use a Specialized Copper Cleaner

While you can certainly use a gentle dish soap to wash your copper mugs, there are several formulas that are designed specifically to target the needs of copper mugs, to prevent tarnishing and damage. Bar Keepers Friend is a soft cleanser that will give your copper mugs a polish and keep them scratch-free, unlike other, harsher cleansers.

5. DO Store Them in the Open

Since moisture will collect on copper mugs when they’re stored in enclosed spaces, which will most likely lead to the development of a patina, the best place you can store them is out in the open. A shelf, a decorative dining display, or hanging art in your kitchen—these are all great places for storing your mugs that will allow them to breathe and will keep your living space looking classy.

The right care for your copper mugs will not only keep them looking shiny and new for longer, it will also prevent copper from leaking into your future cocktails, which has the potential to be a health hazard. While all copper is bound to tarnish over time, proper care for your copper mug will ensure that they stay bright and beautiful for years to come.