Bob; I did not get them hot enough to turn blue, not as far as I could see though I would also like to add that after a few trials with less than great results I lost interest in investigating the matter further. I would also like to state that the PS300 is far from the worst of the big brands, the Makita that I got to replace the first Bosch was the worst of the lot, even when trying to cut a curve in plywood the blade would pop from the guide roll and veer off... As I have faith in Makita I was bot surprised and disappointed.
Update: I ran into an old colleague who uses the PS300 and who is a skilled carpenter. He was one of those trying out the Carvex, ending up returning it.
He runs a PS300 and he was always very pleased with it and said it was superb. I asked him specifically if he had cut any thicker material with it (35-50mm) and he said he wasn't sure if he had really checked the squareness of the cuts as he assumed they were square. He asked to get back to me on that and got back to me this weekend and he could - to his disappointment - confirm that he could not achieve square cuts in 45mm soft wood when marking up and chopping down a 45x90mm piece just to try it out. They would invariably start out square and then deflect regardless of how he went about it.
I am not trying to convince people Bosch is superior, just that my experience with them jigsaws have seen me starting out with the old GST85PE, then going very briefly to a Makita - which was the worst of the lot - to Festool PS300 and then to the Bosch GST135CE and then back to the Bosch GST85 because I figured it was the best of the bunch. (Mafell's P1cc monster did worse than Bosch and probably worse than Festool when using regular blades on the demo I attended and I could not see myself forking out for those verrrry expensive blades to get a better cut in those few instances when you want a cut "on par" with a circular saw for smaller tasks and haven't bothered to bring the circ saw.
I have no faith in jig saws for "fine woodworking" but for general construction they are handy. Just wish they'd cut better in thick material.