OG much lower than expected, but post mash gravity was close

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

Hops and Brains

New Member
Joined
Jan 28, 2020
Messages
2
Reaction score
2
This weekend I brewed an IPA with an expected OG of 1.061. My post mash gravity was 1.053 (expected 1.054). Pre-boil and post-boil volumes (6.5G and 5.5G) were as expected. How did I end up with an OG of 1.056. I'm no scientist and relatively new at brewing but the boil evaporates the water... not sugar. So shouldn't I have been closer to the expected OG if my wort volume reduced as expected? I don't recall ever being this much off before if my mash gravity was right.

Additional notes: I'm using Beersmith for making recipe and calcs. Equipment is 35L Brewzilla.
All grain. Just 2 row and maris otter. No sugar additions.
This was the first time I milled grains at home and think I went a little to fine with a portion of the grist which led to some pump clogging. But got through the mash alright and was very close to the expected gravity at that point.
I used only a refractometer for checking my mash gravity. Checked it while hot (1.052) and retested when the sample had cooled, which was the 1.053 reading. Used the refractometer, a hydrometer, and tilt for OG (1.056). All 3 were the same for OG.
 

hotbeer

Opinionated Newb
HBT Supporter
Joined
Mar 10, 2021
Messages
1,666
Reaction score
1,212
If your pre-boil volumes and SG were as expected. And your post boil volume was as expected, then I'd think there was a measurement error somewhere.

Or perhaps you changed a setting in the software for something that gave a bad calculation.

Maybe even mixed up Imperial gallons and US gallons if your software allows that distinction.
 

VikeMan

It ain't all burritos and strippers, my friend.
Joined
Aug 24, 2010
Messages
4,861
Reaction score
4,309
53 x (6.5 / 5.5) = ~63

So, your post boil gravity should have been about 1.063.

If you measured 1.056 post boil, here are the possibilities:

- your pre-boil volume was not really 6.5 gallons (i.e. it was smaller)
- your pre-boil gravity was not really 1.053 (i.e. it was lower)
- your post-boil volume was not really 5.5 gallons (i.e. it was larger)
- your post-boil gravity was not really 1.056 (i.e. it was higher)

i.e., there's a measurement error somewhere. This is not a software issue, unless you simply trusted the software for one or both volumes, without measuring. (And even then, it would still really be a user issue, i.e. parameters need to be set correctly.)
 
Top