Um just because of flashpoints and things happen, I would never warm my oils in the oven or on the stove. I just go a little higher than warm, because 1) I lack patience and 2) I always had to reheat it again anyway. No, you can't tell. Well you can if you put it in your wax and mix it and there's a sludge or oil outline on the bottom of your pot. Rapture is a heavy, sultry fragrance to me and I love it ... it floated forever while I slowly added vybar and stirred and stirred and kept repeating the process. You don't want the sludge in your wax or the oil slick. It never really solidifies. It just umm makes things ultra messy, especially when using a nice rich red. This is why I do not color until after I know the fragrance will bind. The other FO was a white tea and ginger from someone who said, "we never had issues before so you are doing something wrong." I know the FO came from someone I absolutely refuse to order from again, but I have about 6 of those companies and three of them are OOB. And then there was an ultra heavy oil that just flat did not mix into the wax at all and sat on the bottom of the pot and burned, forcing me to clean and scrub the brown sticky stuff forever just so I could use my pot again. That person, too, is OOB. And it was a terribly rich and lovely FO that I really wanted it to work. I hated losing the wax I had for that, but really I had no choice. Well I did have a choice and I chose to pitch it lol.