Additions... Mash Volume vs. Batch Volume

[petrolSpice]

This has been confusing me quite a bit... When I use Bru'n Water to calculate the Water Additions (gypsum, CaCl, etc...) it says to enter my Mash Volume. I compute the salt additions to meet the target mineral profile in this volume of water.

However, as I boil the wort, the water is leaving but the minerals stay behind. So the ppm of the minerals after boiling is going to exceed the target by a decent amount.

To me it makes more sense to use the post-boil (batch) volume for salt additions. Then you would also enter mash water volume, which combined with the salt additions and gain bill gives you the mash pH.

What am I not seeing here?

 

[spittybug]

Do you not sparge your mash? The boil volume = mash volume + sparge volume, right? Remember, some gets stuck in grain bed.

 

[dmtaylor]

This has been confusing me quite a bit... When I use Bru'n Water to calculate the Water Additions (gypsum, CaCl, etc...) it says to enter my Mash Volume. I compute the salt additions to meet the target mineral profile in this volume of water.

However, as I boil the wort, the water is leaving but the minerals stay behind. So the ppm of the minerals after boiling is going to exceed the target by a decent amount.

To me it makes more sense to use the post-boil (batch) volume for salt additions. Then you would also enter mash water volume, which combined with the salt additions and gain bill gives you the mash pH.

What am I not seeing here?

Great question. Personally I use post-boil volume for my additions. Otherwise the salts may become too concentrated. Worthy of note: I brew 1.7-2 gallons post-boil typically, so my boiloff rate is roughly 30%, which is WAY different than the commercial or standard homebrew rates. So for small batch brewers especially, this makes a lot of sense. For big batch brewers, adjusting salts for pre or post boil volumes doesn't make nearly as much difference. Things to consider.

 

[petrolSpice]

Do you not sparge your mash? The boil volume = mash volume + sparge volume, right? Remember, some gets stuck in grain bed.

I do no sparge BIAB, so my starting volume is the full mash volume, and that's the volume I used for the salt additions.

I lose water (and minerals) in the grain yes, but this is not what concerns me. If I'm boiling off 20% of the water then that means the minerals are 20% more concentrated in the post boil wort.

Just curious if I've been doing it wrong.

 

[petrolSpice]

Nobody knows?

 

[mabrungard]

Pro's typically boil off around 8 to 10 percent. Homebrewers are often losing much more. Your 20 percent is high and you should be accounting for that extra loss in your mineral addition calcs. Either reduce your boil off loss by reducing boil vigor, partially covering the kettle, or calculate the minerals based on a smaller volume.

Normal boil off is a reality we all expect, but excessive boil off can over concentrate the salts.

 

[petrolSpice]

Pro's typically boil off around 8 to 10 percent. Homebrewers are often losing much more. Your 20 percent is high and you should be accounting for that extra loss in your mineral addition calcs. Either reduce your boil off loss by reducing boil vigor, partially covering the kettle, or calculate the minerals based on a smaller volume.

Normal boil off is a reality we all expect, but excessive boil off can over concentrate the salts.

I boil off around 15% in a 60 min boil (1.25 gal/hr), and that's with a fairly low-vigor boil.

However I think it's a slight oversight that this isn't mentioned in your calculator (or maybe I didn't see it?) since it's mostly homebrewers who use your calculator.

In the meantime, would it be correct to first enter the batch volume and use this value to compute salt additions (in grams). Then change the volume to mash volume to estimate acid additions for mash pH?