It's all thanks to the The Grey Book which forces you to lay down lights on the grey paper page first.
When
it works well it helps to short-cut the dreaded 'pencil first' tendency
that tries to sneak in from time to time. The looser the initial
white is - the better the sketch turns out - and the pencil doesn't
even get a look in.
The
old Victorian houses in Albany Road, Ponsonby are perfect for trialing the technique and it makes the decorative white fretwork stand out nicely.