The uses of birch bark oil:
Leather and wood sealing. (if mixed with linseed oil it goes deeper in the wood)
Protection from bacterial and fungal infections.
It's flammable and can be used as a candle or lamp oil.
Birch bark tar:
It's waterproof, and can be used as for example, sealing a birch bark canoe.
And of course as a glue. (Otzi's axe head was hafted with birch bark tar, 5.300 years ago.)
To make tar; boil the oil, let it cool for awhile to see the consistence, if it is too hot, it will be thin. If you let it boil for too long, it will become carbon.
Please only use bark from dead trees.
A better use than a cookie can, could...