All grain help: Where did I go wrong??

[_Bryan]

Howdy all,

I've been experimenting with small all grain batches BIAB. Using Beersmith, I scaled a recipe and tried to make it today. Unfortunately, the pre-boil gravity was much lower than the recipe said it should be. I'm wondering, where did I go wrong? The recipe is below:

Batch size: 1.5 gallons
Boil size: 3 gallons

3 pounds of 2 Row
12.40 qt of water at 159.5 (hit this)
Mash at 152.1 for 75 minutes (I hit ~151 after adding the grain, close enough I would think)

After the 75 minute mash, the recipe from Beersmith said the pre-boil gravity should be 1.041. I ended up with 1.016 after measuring with a hydrometer.

So, I'm wondering if I didn't scale the recipe correctly. Does the 3 pounds of 2-row sound about right for this batch? Any other thoughts?

Thanks much guys!
Bryan

 

[LLBeanJ]

3 lbs should be enough for a 1.5g batch at average efficiency. Was the grain crushed?

A couple of other possibilities...

1. Are you confident of your pre-boil volume? It wouldn't take too much extra water to dilute the gravity.
2. Was your hydrometer reading corrected for temp? Wort warmer than 60°F will require adding points to the reading to be accurate.

Edit: Just messed around with some numbers in BeerSmith...
@ 75% efficiency, 3 lbs of 2-row mashed in 3g water should yield 1.027 pre-boil, assuming 1.5g post-boil volume and will yield 1.055 OG.
To get up to 1.041 pre-boil would require 4.75 lbs of grain and would yield 1.082 post-boil, assuming the same volumes as above.

 

[LLBrewer]

I'd bet your wort was hot when you measured the preboil gravity

 

[_Bryan]

@LLBeanJ - Yes, it was pre-crushed.

Yep, it was hot. It was at 148F when I measured it. And you are right, I didn't think about the hydrometer reading needing to be adjusted (doh!).

So, if I plug my numbers into the Beersmith Hydrometer adjust tool:

Measured gravity: 1.016
Temp: 148F
Corrected gravity is: 1.033

So, that is closer to where the recipe calls for but not quite. Could anything else account for the remaining difference?

 

[LLBeanJ]

Honestly, you cannot get to 1.041 with only 3 lbs of grain for the volume you described (3g pre-boil). According to my numbers, hitting 1.033 would equate to 90% mash efficiency, which is near the extreme high end for BIAB.

At 100% efficiency, 1 lb of 2-row has the potential to yield 36 gravity points. So, 3 lbs would be 3 X 36 or 108 gravity points. With 85% efficiency (more realistic than 100%), multiply the 108 x .85 and that yields about 92 points. Divide 92 by 3 gallons for your pre-boil and gives you a pre-boil OG of 1.031, give or take a few points depending on close you are to 85% efficiency.

Also, I would be a little suspect of your corrected gravity reading. The warmer the wort, the less reliable the corrected reading. I usually make sure that my wort is below 100°F before taking a reading and then correcting for it.

Take another look at your recipe. Are there any other fermentables besides the 2-row? Any extract or simple sugars that are causing the OG to be higher than you achieved?