I am rebuilding this post (WIP)
I cut a lot of firewood each year, all of it Birch. I was trying to figure out how I could utilise the tree fully as it seemed wasteful to put all that bark through the woodstove. Somehow I stumbled on an article about Birch tar and got very well drawn in by the process and history of it. Started making it and using it, and found it extremely useful and very good at treating / waterproofing wood and leather. It also imparts a very unique smoky smell that is long-lasting on anything you apply it to, Russia leather was well known for this.