I'm curious as to why accounting for boiloff mineral content would be of concern? I say this because in previous threads we agreed the amount of strike water added to the mash, as in mash thickness, has a minimal effect on alkalinity or pH.
Mostly because we are dealing in Excel and it's easy to track so why not do it. As an example, let's use Ca and Cl content:
Say I strike with 28.77 liters in a no-sparge mash. My source water has 35.9 ppm Ca and and 30.64 Cl. I supplement with 2 g of Anhydrous CaCl.
My Pre-boil concentrations are 61 ppm Ca and 75 ppm Cl. My finished (Post-boil) concentrations, with 10% boil-off, are 65.81 Ca and 80.96 Cl.
Now jack it up to 15%, which I'd venture to say is probably close to standard for the average user, and those numbers become 68.11 for Ca and 83.79 for Cl.
Huge deal? Depends on the brewer but if you are using Excel anyway, why wouldn't you just track it?
For Martin, it would be as simple as making a new row under Row 15. Row 15 isn't actually the finished water profile, it's just the pre-boil water profile. If a user input for boil-off was added (it's shown , the new code becomes:
=(Pre-Boil Concentration (ppm)*SUM(Strike,Sparge))/(SUM(Strike,Sparge)-(Boil-Off))
which could then be dragged across the row.
Now notice the line, "For Martin, it would be as simple..." and chuckle to yourself, especially if you are like me and you do your stuff in Excel, at how flippantly I toss that line off...