It works in any position, but the vapour from th plastic is hot, and rises - then covers the lens. However, the main reason at the time I made the video, was that the focusing lens inside the laser wasn't fixed at the moment - they fell out if I turned the laser upside downpullbangdead said:Maybe a silly question: does it work if the laser is aimed downward onto the plastic, instead of upward? Both videos show it being upward, at least that's what they appear to show.