Brian Sharrock wrote:

Sometimes; you have to switch ON a CF 'bulb' in the morning if
you want to read by it in the evening! OK! That's a slight hyperbole;
but they are slow to come to full brilliance. They are fine for
lamps which will be ON for hours ... but not for places where
the lights will be switched ON for short periods (toilets, bathrooms,
bedside lamps, for instance)


Again, I've found this to vary greatly between makes. Some are very
poor, taking 10mins or more to reach max output, while others do so in a
few seconds.

--
Grunff