Silver Birch Tree Training/Pruning

All I know about silver birch is that they "bleed" sap in spring as we used to tap ours to make Birch Sap wine. You don't want to prune them when the sap is rising.

Ooh, I was just watching a YouTube video a few days ago about this, except the YouTuber liked to just drink it neat while sat under the tree in the morning. I tried fizzy pop made with it in the US a couple of years ago, and that was an interesting flavour - I thought it would be nicer without the fizz. 

I'd really like to try it and may see if I can give it a go next year if the pandemic allows me to visit my Grandma in the spring (I haven't seen her since Christmas Day 2019). She has a big garden with several silver birch trees that she planted about fifty years ago, so I reckon they would give a decent amount of sap. Of course, this is dependent on her allowing me to put a hole in one of her trees (and still being here into her 93rd year), but I think she would be quite interested to taste it herself!