Mercury Vapour bulbs contain mercury; flourescent tubes do not. We seem to be
having difficulty with US and UK usage.
Some MV bulbs have colour correction phosphors but they are not flourescent
tubes. The strange element is included in the starter in the flourescent tube.
The advantage of the MV bulb designed for graphic art usage is that its distance
can be varied from the workpiece, but still with even coverage, giving greater
flexibility in the size of the print one can use with it. One needs more tubes,
long thin things, to cover the same size of print.
Terry King