You have to cure the fan leaves in a similar way to tobacco leaves. That guy Jean Carlos that makes the expensive Magars talked about it before, he called it "color curing" and said it was similar to cigar technique.
I'd probably start by experimenting with some tobacco broad leaf curing tutorials like this:
Tobacco Fermentation / Curing Chamber for Cigars: Tobacco is an age old, yet amazing plant, which has become increasingly popular among hobbyist in recent times! Perhaps it is a distraction from daily stresses and allows an escape to simpler times. For some, growing tobacco is an absolute obsessio…
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