Are you claiming that when an aircraft takes off during snow showers and within the allowed hold-over time, thanks to the magical effect of glycol, the snow instantly turns into water and the wings just look wet, as though it was just raining? There is no presence of slush, partially melted snow, snow crystals, nothing that has consistence?
Yes, where the aircraft has been anti-iced with a Type II or IV fluid. I'm not a chemist but I believe this takes place due to chemical action rather than magic.
Due to the thickening agent present in Type II and IV de-icing/anti-icing fluids these fluids are able to remain on and protect aircraft surfaces for a period of time (see holdover time tables for applicable times).
As the snow flakes impinge on the fluid film they melt, due to the low FP of the glycol in the fluid, progressively diluting the fluid and yes the surface does look wet at this stage. Depending on the intensity of the snowfall it may take a few seconds for the individual snow flakes to melt but once slush or snow is seen to be building up on the fluid film the holdover time will have expired and a further treatment will be required.
The viscosity of the fluid is relatively high when applied to the surfaces of an aircraft on the ground, however, as the aircraft accelerates during take-off the shearing effect of the airflow over the wings breaks down the structure of the fluid, reducing the viscosity and allowing it to flow off to provide a clean wing. Clearly if the fluid film has snow on top of it, it will be prevented from working as designed.
In fact there is, and that is why the Regs, here anyway, still allow take-off as long as none of that stuff adheres to the surfaces.......
It would be appreciated if you could let us know where, in your regulations, it allows you to take-off with snow/slush present on top of an applied film of anti-icing fluid...