Frosted glass is glass with at least one side rough, scattering the light passing through. It is therefore translucent. In my office some different material is placed over some windows producing similar effect.
In both cases applying substance of similar refractive index, which has the property of filling the pits on the material, like oil or glue and creating a smooth surface turns translucent surface into transparent.
I found a mention that translucent vinyl cannot be made transparent in this manner. Is that the case too, and what's the reason?