Tom,
It is Lavender Spike Oil that is used in finishes and not likely the stuff at the health food store. Also, it is my understanding that Lavender Spike oil retards drying, at least in spirit varnishes. I have, at least, been working under that understanding; adding more Lavender Spike oil to my violin varnish to slow down the drying some which usually only takes a few seconds with a spirit varnish. By the way, that stuff is potent. A drop is enough to drive me out of my shop. I keep the stuff in a glass jar inside a plastic bag to so I can stand to enter the room in my shop where the finishes are stored.
Mark E.