Am I correct in calculating my CaCl and gypsum additions on total mash volume? I'm asking because with biab my mash volume is more than traditional all grain therefore I add more.
For flavor it is probably best to add salts based on post-boil volume. But for simplicity, yes, you could also use total mash volume.
If you are adding the salts for flavor, add them after the mash. Post-mash Kettle additions are the same regardless of whether you're doing BIAB or not.
I worried about this too for a while, but from personal experience, I have had excellent results with my water profile just adding all of my salts and pH adjustments (lactic acid for me), to the mash before mashing in (BIAB). It probably concentrates the mineral profile a bit more, but it hasn't negatively affected my beers in any way, and its just simpler to add it all at once. Although to be fair, I only brew mixed ferm saisons with an overall soft water profile target, so YMMV.
