Another poster mentioned off-list that new-minted cakes are often dried
with steam pipes, but not in the sun, which is said to damage smell and
taste. Since so much mao cha seems to be sun-dried, this raises some
questions.

Light seems to be bad for tea in general, causing both loss of
flavor/aroma and sometimes the development of off-flavors. The former
may not be so serious in most cases, since loss of (say) 20% of flavor
or aroma probably isn't detectable to most people, so long as the
general balance is maintained. But many of us know how quickly light can
harm bottled beer - and how unpleasant the resultant "skunking" can be.
Whether photochemical, thermal, autoxidative or any other, damage that
creates bad stuff is probably much worse than damage that reduces good
stuff.

It seems unlikely that mao cha would be immune to photo-degradation. Is
it possible that the only reaction is loss, and not much at that? Could
the heavy leaf structure common in Pu-erhs be relevant? The somewhat
variant chemistry of those strains? Is it possible that whatever
off-flavors may develop are removed by chemistry, biochemistry or just
aeration when cakes are formed and pre-aged? Or are we just used to that
style, since it's the norm?

The few mao chas I've tried tasted only somewhat like finished Pu-erh,
even fresh sheng cakes. Perhaps the elements that are most sensitive to
sunlight aren't even present in fresh mao cha? Analogies might be coffee
and chocolate, where the green beans/nibs are much more stable than the
roasted product, with its new suite of volatile and fragile chemistry.

Beyond academic technicalities and mechanisms, is there another useful
distinction here for drinkers? For example, can one buy cakes made only
from "shade-dried" mao cha; and if so, are they any better?

-DM