Complex sentence: Cold porcelain is a cheap, non-toxic, easy-to-work-with alternative to porcelain, which does not require heating since it gets hard by exposition to fresh air.
Split into simpler sentences: Cold porcelain is a cheap, non-toxic, easy-to-work-with material which in some applications may be considered as an alternative to porcelain. It does not require heating since it gets hard by exposition to fresh air.