The best times to harvest shadows are at sunset and sunrise when they grow the longest.
They’re harder to cut, though… so most mages wait until noontime, when the sun is brighter.
Natural shadows are best for magic spells.
No self-respecting wizard would use a shadow made by torchlight or candlelight for an important spell. They do not have the same power. And they are wilder, harder to control.
And harvesting your own is important. Residual aura conflict can result in spectral friction.
Which causes explosions.
And for us to bill your parents for the damage to our labs, student.