There are two reasons why clear parts can have an imperfect surface

1. The wrong mould material was used

For casting clear polyurethanes, use only silicone HQA40 material, which is a translucent silicone.

Only addition cure silicone should be used for clear polyurethane casting

Condensation cure silicones will cause inhibition and leave a sticky surface.

2. Release agents were used

For perfect surfaces, no release agents can be used, as they give the surface a structure that looks opaque or spotty.