The wick channel you refer to is usually called the diaper, And that is what burns first, and like Katya said they all burn eventually.i know this is an unpopular position. popping is harmless in some instances but i'm not going 80/20 rule on this. waiting until the taste is bad? that works but reminds me of the ABC (Australia) piece on electronics reclamation in china. poor woman was burning and inhaling components to test the chemical content.
there's a wide variety of carto implementations. that's a good thing but the variance as far as safety is a concern. by wick channel i mean those where the wick effectively isolates the polyfill from the heating element. good cartos are not necessarily the acclaimed or expensive ones. i'm glad folks are testing these for themselves.
