Hi! Thank you for this post :)

I also do cosplay and I start to use resin but I face a difficulty, could you help me?

I made a mold using this (40mm diameter half-sphere):
It's a silicone gum, the saleswoman confirmed to me that it is indeed material to make resin mouldings.

In the end, my resin has a kind of whitish shadow at the lowest point. Do you know what could have caused this?
We see it vaguely on these photos, it is difficult to take a picture because of the reflections but in reality it is obvious.

Do you think it's dust ? Did I miss mixing the two phases?

Thanks for your answer :)