Not polished ice but...
I've seen in FAR 91 type flying the practice of accepting loose snow on the wing, believe it will always blow off on take off. May be true in cases of dry snow, I'm not so sure that when it gets a bit wet, or sticky, this will happen. So I've found that blowing gently on the snow on the wing, or just flicking it with a finger, seems to be the sensible test. If it readily repositions itself well away or completely off the wing, seems sensible to take off. If it at all just moves over a bit, and stops, then it filts definition of adhering.
The wording of the FAR addresses snow "adhering" to the wing. Has there been any clarification on exactly what adhering has meant?
Before anyone jumps in admonishing me for not using common sense, I only pose the question because I KNOW pilots different opinions on what adhering is meant to imply.