![I feel like this is a good one. I put this ceramic mug in the microwave sometimes and overtime this black sludge appears in the outside? What is it and why do I feel like this is a good one. I put this ceramic mug in the microwave sometimes and overtime this black sludge appears in the outside? What is it and why do](https://preview.redd.it/omkr9m7r1ld01.jpg?auto=webp&s=5b4fab7ea6f97c9b65983ebbbb4038008faa7ac2)
I feel like this is a good one. I put this ceramic mug in the microwave sometimes and overtime this black sludge appears in the outside? What is it and why do
![What is the Difference Between Cup and Mug? - Mugs.Coffee | The best and coolest coffee mugs in the world What is the Difference Between Cup and Mug? - Mugs.Coffee | The best and coolest coffee mugs in the world](https://www.mugs.coffee/wp-content/uploads/2023/02/redcupvsmug.jpg)
What is the Difference Between Cup and Mug? - Mugs.Coffee | The best and coolest coffee mugs in the world
![What is the Difference Between Cup and Mug? - Mugs.Coffee | The best and coolest coffee mugs in the world What is the Difference Between Cup and Mug? - Mugs.Coffee | The best and coolest coffee mugs in the world](https://www.mugs.coffee/wp-content/uploads/2023/02/cupvsmug.jpg)