Why Does It Take Longer to Reach Target OG in Bigger Beers?

[Gustatorian]

I recently brewed a big barleywine (1.110) and it took an extra hour of boiling to reach target OG. My boil-off rate is honed in for average OG beers on Beersmith, but not for bigger beers. Can anyone explain the science behind it?

 

[wilserbrewer]

Did you collect more runnings?

Did you actually measure the boil off and actual volumes or are we talking about what beersmith predicted?

If your grain absorption is flawed in beersmith you would have extra wort with a high gravity beer that would need a longer boil to reach the predicted volume.

Do you measure volumes and gravity as you progressed?

 

[mattdee1]

I ran into weird results the first few times I strayed into that range of OG.

What I didn't realize, which in retrospect seems obvious, is that if you apply the same process to really high OG beers that you would use for low/moderate OG beers, then your efficiency plummets.

As an example, let's say you're mashing 20lbs of grain in an attempt to make a 5gal batch of 10ish% ABV beer. If you use your normal process of only collecting enough runnings to do your usual 1 hour boil so that you end up with 5gal into the fermentor, then you're probably going to find that you're missing your target OG by a country mile (on the low side).

To get all that sugar into your kettle to hit your desired OG, you pretty much have to treat it like you're collecting enough runnings for a 10gal batch of mid-OG beer, then do a much longer boil to get it down to target volume of 5gal.

Or, you need to compensate for the poor efficiency with a LOT more grain, but that's probably not an option because your MT would need to be enormous.

 

[ESBrewer]

Boil off will diminish when the amount of solutes such as sugar in water/wort increases. This is because solutes will increase the boiling point of water and more heat energy will be required to boil the wort and evaporate water. This is because the energetics in the solution will change. In pure water, small water molecules interact with each other, in a strong wort there are plenty of other molecules that interact with water leading to a situation where it takes more heat energy to release water from the surface (not wanting to go to the exact physical details that I am not so familiar with). This is one reason, there could be additional factors in your case, though.

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