When I put large bed sheets in the tumble dryer they sometimes roll up into a ball and are still wet when the drying cycle has finished.Since smaller items do not seem to do this is there a threshold at which the area of the fabric gets too big for the dryer and rolls up? Would folding it a few times to make it smaller help and what effect would this have on drying time as if you fold it too many times this would have the same effect as it being rolled into a tight ball and it not drying properly? Has anyone devised a cunning method of putting their large sheets into the dryer that stops them from rolling up?Paul GaultNewcastle-under-Lyme, UK.

Recently, a friend of mine did his 8th grade science fair project. He decided to test whether pure water, water with flour in it, or water with salt in it would evaporate (and thus be purified) the fastest. He found that the flour went the fastest, the salt was next, and the pure water was actually the slowest. He did say that he used the same volume of total liquid overall, not just the same volume of water, so that could have been a factor by decreasing how much needed to be evaporated. But the margin was too large for this to be the only factor. Does anyone know why this would happen?