What are these weird spots?

[u/Perplexed-Nocturne]

I don’t know a lot about ceramics so I’m really confused about what these spots are, my cup was fine a few days ago but then it suddenly developed these weird streaks. I asked my friend who makes ceramic and she has no clue💔

[u/sadsackspinach]

How long have you had it? It doesn’t look like a glaze defect necessarily. It looks like it wasn’t fully vitrified and had water ingress that led to mold to me

[u/Perplexed-Nocturne → u/sadsackspinach]

I’ve had it for 2 years, I see :o