The newest version of Thermal expansion adds a button in the GUI of the induction smelter to lock the flux spot. It isn't showing in the latest release. I was banging my head on the wall trying to figure out why I couldn't put stuff in the 1st slot to make hardened glass. If anyone else has the issue, the button doesn't show, but if you mouse over it(just under the middle slot), you can still push it to lock/unlock it.
All in all, this pack is truly beautiful. I love the higher resolution while staying so Faithful to vanilla. Pun intended....Definitely my favorite texture pack. Thanks for all the hard work.