hi
I am using a fiberglass mold. and I apply Gelcoat with paint on it. but after several time surface of the mold is matt and is not glossy and someplace when I watch the surface of the mold I can see some Gelcoat and paint cured on the surface mold. please help me how can I remove it?
in this area when I apply again new gel coat and paint it become matt and final products in some area is matt.

please let me know how can I clean the surface of the mold?
before I used some kind of acid and also acetone but nothing happened.

tanks so much