Level 80 Synergy achieved 4/18/2011 after casually leveling it every now and then. Now to cap clothcraft and get goldsmithing to 60 to prepare for the next update and take it to 100!
@Drayco
Impurity ratio is what causes the furnace to explode. If it goes above 30% there's a chance it'll blow up. To prevent this you have to use the safety lever and reduce it to under 30%. Or if it's already about to explode you whack it with the wrench and say a prayer.
I dont understand the pressure and impurity ratio's yet... The fewell is really quiet simple. You have a current status (top numbers in white) and a target goal (bottom numbers in yellow). To complete your synth, you have to meet or exceed the target goals on each element.
This is what I have learned from a small handful of successful synths and power leveling by spamming fewell...