# Mash Efficiency Correlation to Boil Off

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#### Knee Deep

##### Member
Hey All,

Had a weird occurrence happen last weekend, and I'm curious what might be the cause...

We brew all grain with 3 kettles (HLT, Mash, Boil). We had what I believe was a really efficient mash. Everything hit at all the right moments, and things felt good. Then the boil hit, and we didn't boil off nearly as much as we typically do. For reference, typically we'll move roughly 7 gallons into the boil kettle from the mash/sparge, and boil off close to 2 gallons. However, on this brew, we boiled off only 1 gallon.

So the question I immediately had was: If our mash is more efficient, will we boil off less?

Any thoughts?

#### day_trippr

##### The Central Scruuuutinizer
If the question is "Does higher specific gravity wort boil off at a different rate?" I'm going to go with "Outside of some theoretical extreme resulting in a huge gain in SG, probably not".
Boil off rate is an localized energy-input vs dissipation model that's decoupled from mash extract/lautering efficiency...

Cheers!

#### doug293cz

##### BIABer, Beer Math Nerd, ePanel Designer, Pilot
Staff member
Mod
HBT Supporter
Boil-off has no direct effect on mash efficiency. Mash efficiency is determined at end of lauter, prior to any boiling. You should have the same amount of extract (primarily sugar) in your BK at end of boil as you did at the beginning of the boil, unless you added sugar to the boil after the mash, or had a significant boil over.

Planned boil-off can have a small effect on mash efficiency in that planning for more boil-off will increase your pre-boil volume, and higher pre-boil volume will increase your lauter efficiency somewhat (all else being equal.) Boiling off more or less than you planned does not affect efficiency, as the pre-boil volume wasn't affected.

If you want to really understand your efficiency, you need to track volumes, SG's, and grain weights accurately. If these inputs are not accurate, any calculated efficiencies will be inaccurate.

Brew on

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