Rectified birch tar oil is derived from Betula alba and is very smoky with leathery notes. Birch tar oil needs to be extremely diluted because of its strength. Only a small percentage of the rectified oil is allowed under IFRA guidelines, but a tiny amount is all you need. Cade oil provides a similar smoky note to birch tar, but cade comes from Juniperus oxycedrus. Both cade and birch tar are dark liquids.