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.
Gives a very durable, waterproof finish with a patina type sheen. Repels all types of insects and is extremely resistant to mould and fungus, and the smell as mentioned is quite special. An ounce of tar is enough I would wager a guess to do anywhere from 10-15 handles of regular size. I will post some pictures of different types finished with tar in the near future. I have one fella that buys it off me fairly regular for his rifle stocks.
Birch Tar: $30 CAD per Fluid Ounce
If you are interested in anything to do with Birch bark just let me know I can probably make it happen.