eine Möglichkeit:

Weitere Möglichkeit:

gray film/haze geht bei Kunststoffen, auf Glas fogging

'A gray film' seems most likely to me, or you could also rephrase with an adjective, which might be more typical in English. E.g.,

Despite several attempts at cleaning, the surface remained noticeably clouded / mottled.

Of those three, 'mottled' is the least uniform, suggesting splotches here and there, not a single coat or layer that's the same everywhere.

Context, as ever, might have helped.

Fog and haze are usually more for air, but fogging or hazing could possibly be for a transparent surface such as glass.

'Bloom' sounds the least likely of all on the face of it, but it might be exactly the right word in some specific technical context.