I am a lover of the flat bed scanners by Epson and Canon ( -the v700, v750 and 9000f ) for photo scanning.
These are great scanners but they suffer from one huge drawback - scratches.
When I get a scratch on the glass that area is covered and that part of the scanner will not be used for scanning again. This is an irritating process but necessary to maintain image quality.
So how do we get the scratches ? I use a velvet LP cleaning cloth to remove dust. This is effective but if there is a bit of grit carried on a photo it can potentially damage the glass surface. It is a balance between removing dust and the danger of harming the scanner. Blowing the surface with an air duster is useful but not totally effective in removing particles. At Saturn Films 1969 we use a positive pressure cabinet to keep dust out of the working area and this helps reduce the need to physically clean the scanners. At the end of the day though there will always be a bit of dust carried that will result in scratching the glass surface. We have to be alert for this and to take action when it happens. Even when it means junking a scanner!