I've always attributed it more to just moisture. I guess it could be tar. When the tobacco burns, it releases steam. It also releases heat that dries, but by the final third, enough moisture has been pulled through to make the tobacco wetter and less wanting to burn. At least that's my theory, and even if I'm wrong, I'm sticking to it because everything else is fake news.
I also routinely encounter this thing where the draw gets tighter as the cigar burns. I've chalked it up to the added moisture making the tobacco swell. I often have to push a hole in after half or so of a cigar.
LeeBot wrote: