![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
![Personalised Printed Coffee Mug - Coffee is a Hug Inside a Mug | Giftr - Malaysia's Leading Online Gift Shop Personalised Printed Coffee Mug - Coffee is a Hug Inside a Mug | Giftr - Malaysia's Leading Online Gift Shop](https://giftr.my/cdn/shop/products/yZ0HnUFk6r.jpg?v=1589267414)
Personalised Printed Coffee Mug - Coffee is a Hug Inside a Mug | Giftr - Malaysia's Leading Online Gift Shop
![mug noun - Definition, pictures, pronunciation and usage notes | Oxford Advanced Learner's Dictionary at OxfordLearnersDictionaries.com mug noun - Definition, pictures, pronunciation and usage notes | Oxford Advanced Learner's Dictionary at OxfordLearnersDictionaries.com](https://www.oxfordlearnersdictionaries.com/media/english/fullsize/c/cup/cups_/cups.png)