BIAB Question

[C-Rider]

stux, I just finished a brew day making a munich dunkel and I carefully measured my volumes and gravity both pre and post boil. I was wondering if I got 'a neat double-check'. How do you calcuate efficiency with those numbers?

My pre-boil was 1.047 @ 6.875 gal (26.02 L)
My post boil was 1.055 @ 5.625 gal (21.29 L)

Perhaps this link can be used both times?

Brewhouse Efficiency Calculator | Brewer's Friend

 

[Prymal]

You need to post your recipe in order to determine efficiency.

 

[stux]

1.047 x 6.875 = 47 x 6.875 = 323 points
1.055 x 5.625 = 55 x 5.625 = 310 points

The points is basically your total sugars, and both readings are fairly close, perhaps the average of 316 is right

You need the weight of grain to work out efficiency tho

Say you had 12lbs of 34ppg grain, that'd have a potential of 12 x 34 = 408

316/408 = 77.5%
323 = 79%
310 = 76%

Most likely the difference between the two efficiencies is due to measurement errors

 

[1MadScientist]

Thank you stux for that math lesson.

perhaps I'm off because the pre-boil temp was around 190 degree-ish F and the post-boil was at 60 degrees F, a difference of 4%.

I did the long hand math on this based on my Beer Tools Pro using what they call 'Original Grav. (lb/gal)' which looks to be the 'ppg' # and I was within 16 thousandths of a percent. I understand 'Moisture' is also part of the formula.

I got 81% with 11.36 lb of grain and my grain absorption after squeezing is .055 gal/lb.

 

[stux]

Thank you stux for that math lesson.

perhaps I'm off because the pre-boil temp was around 190 degree-ish F and the post-boil was at 60 degrees F, a difference of 4%.

I did the long hand math on this based on my Beer Tools Pro using what they call 'Original Grav. (lb/gal)' which looks to be the 'ppg' # and I was within 16 thousandths of a percent. I understand 'Moisture' is also part of the formula.

I got 81% with 11.36 lb of grain and my grain absorption after squeezing is .055 gal/lb.

Yes, the volume needs to be calibrated back to well... 60F if you're hydrometer is calibrated at 60F

I take my Start of Boil and End of Boil measurements when the wort actually starts boiling which is pretty much 100C, and just after I cut the heat, again, 100C. which gets me volumes which are related.

You can then just apply the 4% cooling loss

26L at 100C = 25L at 20C

The programs do all of this for you

(excuse the metric )

 

[stux]

BTW, if I apply the 4% loss to your preboil figure,

1.047 x 6.875/1.04 = 47 x 6.610 = 310 points
1.055 x 5.625 = 55 x 5.625 = 310 points

And there we have the "neat double-check"