Burning

One evening last week we ended up burning paper napkins, we experimented a bit with it, like one piece was burnt while it was just plain folded open and in a single layer, that was going really fast, one big woosh and gone.
Another piece was burnt folded, slower.
Another piece was unfolded, but rolled in a big cigar, that took a bit of time.
The longest took the piece that was folded and rolled up in a cigar, that was very compact and really took quite a bit of time.
Afterwards we discussed the hows, why's and what's to that whole process, including how the oxygen reaches better when not compact and all that stuff.