I have recently noticed that some of my slides have small spots of what looks like mould. Having done some research on what to do about it, I have purchased some isolpropyl alcohol. Can someone advise me on the best technique for using it? I have experimented with a few old slides, and I find that it doesn't evaporate readily, and tends to leave streaks on the slide. Presumably I need to apply a drop to the mould and then wipe it with some sort of cloth to remove the mould before it dries? How do you avoid scratching the slide?