We investigate the solidification of a mixture of maleic anhydride and 2% (by wt) polyacrylonitrile as the undercooling is varied. Such mixtures show banded spherulites with band spacings over an order of magnitude larger than any seen before. We show that these large banded spherulites share many of the same properties as banded spherulites found in other systems. Our experiments suggest an explanation for the minimum undercooling threshold commonly observed for banded spherulites.