Phat
actually isobutane has no propane and only an isomer of Butane <img src="/forums/images/graemlins/shocked.gif" alt="" />which has a lower boiling point <img src="/forums/images/graemlins/grin.gif" alt="" />- around 14 degrees vs 32 degrees for regular butane if I remeber right. <img src="/forums/images/graemlins/tongue.gif" alt="" />You don't burn off "the top" with isobutane like those "mixed cartridges" that you mentioned.

Isobutane does realy make a difference but as YOU know - evaporation will cool the fuel eventually and you must rewarm it or the flame goes away. <img src="/forums/images/graemlins/shocked.gif" alt="" />
<img src="/forums/images/graemlins/smirk.gif" alt="" />Jim <img src="/forums/images/graemlins/cool.gif" alt="" />