Missed finla volume - too much water.

UGH... so my second AG went fairly smooth... start to finish in 4 hours which I didn't think was too bad. However I really missed my final boil volume by about 1 gallon, and I can't figure out why. Beersmith calculated the total water for a 17.3 lb grain to be 9.5 gallons, given that my mash tun holds .75gal water after sparging. I have verified this with other calculations as well. I am almost 100% sure that I measured the water correctly before heating, and I ended up with about 7.5 gal in the brew kettle pre boil. I I use 1lb grain holds .12gal water, the grain should have held almost exactly 2 gallons which means that my mash tun completely drained, which I know is not the case.

I am 99.999999% positive that I measured the water correctly, so are there other grain factors that determine grain absorption? I did use a finer crush on the grain this time. Could that have an impact on the grain not holding as much water?

Thanks,
-J

Crush won't make any difference in absorption, but it will change retention. Absorption is also impacted by the percentage of water in the grain at the beginning. Highly kilned grains are drier than base malts.

Two batches doesn't make a statistical universe. I'd say track your system's performance so you can make adjustments in the future.

Beersmith may have the wrong boil off rate? I dunno, this tended to happen a lot to me, but I finally got it down to where it stopped. I use beersmith. I'm really not sure what I did, I just kind of kept track of my numbers better. Focused more on measurements and planning.

But, it still happens to me sometimes. Last night I ended up with 6.5 gallons instead of 6.

Boiloff rate has a lot to do with humidity so the software can't guess it for you.

The question is, do you suspect you lost volume preboil or post boil. If you hit your expected preboil volume, then you had a higher boil off rate than expected. If you were short on preboil, you have more MLT loss than expected. Maybe a little of each? You can add a little more boiloff/MLT deadspace to the software every batch until you hit the actuals.

If you're using a rectangular cooler MLT with a braid/bazooka, there's a phenomenon I'd call daming. See, deadspace is usually calculated by draining with only water in there. You measure what's left. The problem is, when the grain is in there, the grainbed itself slows or impedes wort from moving horizontally along the bottom of the cooler to the drain/braid. The larger surface area you have on the bottom, the worse it is. Of course, there's no calibration entry in software for this so I'd just add to deadspace a bit.

beersmith said that my pre-boil volume should have been about 6.75 and I was around 7.5. I boiled about 1 gal in an hour, so I hit that pretty close. I am guessing that the grainbed did not retain as much water as my last batch due to the finer crush.

Thanks for the replies!
-J

I had a similar problem in my brew yesterday...which was also my first AG. I also used beersmith. My mash extract volume was a gallon short and my after boil volume was about 3/4 gal short. It was a little annoying.