As has been mentioned, don't mess about with any ice of any kind.
Some figures I gleaned from those fairly intelligent people in research at NASA were that the weight of ice is minimal compared to it's other effects. For example using their Twotter test aircraft and wind tunnels, they found that drag increased by up to 40% and lift decreased by upto 30% when iced up.
Pretty significant figures. However, even more alarming was the movement of the centre of pressure and especially the effects on the tail of the aircraft. Approach speeds were all to cock obviously and the stalling characteristics became "interesting". The test pilots definition not mine. Mine would have been terrifying......
There is some good stuff out there to read up on, but the simple rule is the best. If iced up, have it removed fully and by the correct method. If you can't go back to the bar and fly another day.