I have some photographs behind our bed that I framed last year and I have noticed the white powdery mould has grown, quite dramatically, behind the glass.
So desperate measures are called. I took down all five framed prints, took them apart, removed the powdery mould,and re-framed them. I also took the added precaution of taping the back of them with special framing tape.
I hope that this will keep the powdery mould at bay for a couple of years (at least!!). So now the framed photos are back on the wall and even if I do say so myself, they look pretty good!