What causes a wrapper to split?

[nhcigarfan]

I keep my humi at 65 and never have issues. Generally the core being to wet will split it.

Yep, as the cigar heats the filler up, the wetter the filler the more it will swell. Probably the vendor kept it too wet, once it hit your humi it started to dry and come down to a good rh. Due the nature of leaves and cigars, the wrapper will dry first and the cigar will dry from the outside in. If you had smoked it straight out of the vendors humi it probably would not have happened because the entire cigar would be at the same RH. Next time if you get a soft or wet cigar from the vendor let it sit for a month or so.