This is an interesting discussion, I painted some woodwork last year
using DPBW and I am about to do some more as I decorate other rooms
this month. But I have noticed that the wood I re-painted last year
looks no brighter now than wood that I am about to re-paint that is a
few years old.

Is there a reason that even DPBW yellows so quickly. Im almost
wondering whether there is any point in painting it anway since it
will look the same next year as it does now! Is it in my prep or the
paint I wonder!

Rajeev

BW paint was brought out in the 60s for external use. It contains
certain additives derived from titanium that are beneficially affected
by ultra violet light, in that the UV keeps the paint from yellowing.
The effect is reversible by subjecting the yellowed paint to a UV
light source, E.G. a tanning lamp. In my own home I use only normal
white paint such as Dulux Trade White Paint. I prefer customers who
specify BW as I know that I'll be back to them to repaint a lot
sooner!