Hi Jo, I've just answered your question on the thread TJay started

But I do leave mine in for a long time on a low setting because banana is a "wet" fruit, then I take them out and leave them to cool, they harden when cooling, you also have to make sure your banana is sliced thinly or takes a lifetime for them to dry out, I use a Mandolin slicer that I purchased from Asda to make/slice foods/crisps as it does it thinly.

Julie