Add your fragrance oil at about 185 no matter what kind of wax for tarts. Stir for about a minute (some say two minutes but for tarts, one minute is fine unless it is a heavy oil, then you might need a full two minutes). If you are pouring into clamshells, you need to let the wax cool to the point where it won't warp the plastic, usually about 135 to 150 (depends on your clamshells). If you are pouring into molds or metal scallops, your pouring temp is less important and you can pour hotter. If you are very fussy and like a perfectly flat top without any sunken look, then pour about 140ish (as others said, test and see) into molds. Otherwise, you can pour right after you are done mixing in your FO when the wax is probably 170-175. When making tarts, pouring temps are less important compared to making candles.