Vanish is a PITA IMO.
You really gotta wet the line on your knots, and pull them tight slowly. Then give it a good hard yank, to make sure its not gonna snap.
I have no use for vanish anymore......just a headache if you ask me.
Try some seaguar if you just want fluoro leaders, or P-line for a fluoro mainline. Those are the best I've found so far for ease of use, and strength. They cost a little more, but last much longer.
Sinker