robeer wrote:So I begin by filling the keggle with the volume noted in TWN and then add the amount I entered in section W after the mash?
Everything should be sorted before you brew. You'll need to be more specific with what you are asking, because I add the TWN to the kettle first no matter what prior to mashing. But, I think that would mislead you.
My process, even if I'm withholding water ... I put the TWN into the kettle first. Then, I treat the full volume with necessary brewing salts, measure the volume to ensure accuracy, then transfer desired withheld amount to a holding vessel (growler or carboy).
Dough in, complete mash, pull bag ... add in withheld water before the boil while the bag is draining.
Everyone's process is going to be different. I would imagine that a "radical" maxi-BIAB might require brewing salts be handled differently. For me, it's usually just 2-3L water being withheld from a 46L VAW batch size ... which amounts to a trivial difference from my predetermined mash pH.
SWN will reflect the water amounts that you withhold in section W. The more water you withhold, the more your kettle efficiency will drop ... which the BIABacus will recalculate as you withhold water. TWN and SWN will change slightly for this reason, as will grain totals.
I hope that makes sense, kinda drunk right now.