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exe 02-02-2011 02:22 AM

Mash Efficiency vs Brewhouse Efficiency
 
So, I completed my 2nd AG brew a few weeks ago, and it was the first that I had taken enough measurements to calculate mash and brewhouse efficiencies. I was a bit surprised by the result. Beersmith tells me that my mash efficiency was about 83%, but my overall brewhouse efficiency dropped to 68%. I'm happy with the mash efficiency, but I am surprised that I lost so much efficiency during the boil, and everything I've read so far only gives tips on increasing mash efficiency. Any idea on what I could have done wrong to lose so much efficiency during the boil? What I can change to keep the efficiencies in line?

Preboil gravity was 1.034, rising to 1.038 after a 90 minute boil. I had 7.5 gallons going into the boil, put 5.5 gallons into the fermenter and had about 0.5 gallon lost to trub \ left after hitting 5.5 gallon.

Thanks!!

Walker 02-02-2011 02:26 AM

Quote:

Originally Posted by exe (Post 2606614)
Preboil gravity was 1.034, rising to 1.038 after a 90 minute boil. I had 7.5 gallons going into the boil, put 5.5 gallons into the fermenter and had about 0.5 gallon lost to trub \ left after hitting 5.5 gallon.

Thanks!!

Something doesn't add up there.

If you had 7.5 gallons of 1.034 wort at the start of the boil and you finished with 6 gallons of wort (5.5 in fermenter and 0.5 still in kettle), the gravity of that 6 gallons of wort should have been 1.043, not 1.038.

exe 02-02-2011 02:31 AM

I suppose then this could be a misreading of one of the gravity measurements then? Might be a dumb question, but should the pre and post boil gravity readings be inversely proportional to the volumes?

Walker 02-02-2011 02:33 AM

Quote:

Originally Posted by exe (Post 2606667)
I suppose then this could be a misreading of one of the gravity measurements then? Might be a dumb question, but should the pre and post boil gravity readings be inversely proportional to the volumes?

yes, it's a direct relationship since you are only removing water when you boil and not sugar.

Volume_A * Gravity_A = Volume_B * Gravity_B

As volume decreases, gravity increases.

exe 02-02-2011 02:37 AM

Got it, thank you!

I'll chalk it up to a bad reading this time. If that proportion holds up in the readings, then the mash & brewhouse efficiencies are pretty much always going to be close to one another, right?

Walker 02-02-2011 02:47 AM

Quote:

Originally Posted by exe (Post 2606696)
f that proportion holds up in the readings, then the mash & brewhouse efficiencies are pretty much always going to be close to one another, right?

Well..... no, not really. The "brewhouse" efficiency should not "count" the stuff you left behind in your kettle or anything. It's just a "I got this much wort at this gravity in my fermenter... period."

So, let's say I make some beer and I have 7 gallons of wort in my kettle at the start of the boil with a gravity of 1.040, and let's say that this was with 75% efficiency.

I boil this for a while, chill, and run it into my fermenter and end up with 5 gallons at 1.050. What is my brewhouse efficiency?

Proportions math now.

if 7 gallons of 40 weight wort is 75 percent, then 5 gallons of 50 weight wort is What percent?

(7*40)/75 = (5*50)/X

X = (5*50*75)/(7*40) = 67

SO, mash efficiency was 75%, but brewhouse efficiency is 67% because you lost a half gallon of wort after you boiled and chilled it.

RMitch 02-28-2011 07:07 PM

*noob question*

What IS "efficiency" exactly?

What's it's purpose? To me, it just seems like watered down beer.

For example, my current batch yielded me about 53% efficiency, but a 1.060 post-boil OG. Had I upped my efficiency to the level it is supposed to be, (i.e. larger volume of sparge water), I'd most likely be starting with a 1.030 or lower OG, which wouldn't make for a good big beer, IMO.

Am I just completely confused, or is it impossible to have high efficiency with a big beer?

Walker 02-28-2011 07:11 PM

Quote:

Originally Posted by RMitch (Post 2690315)
*noob question*

What IS "efficiency" exactly?

A measure of how much of the sugar you are able to extract from your grain.

Quote:

Originally Posted by RMitch (Post 2690315)
What's it's purpose? To me, it just seems like watered down beer.

It's purpose is to let you know how much "mileage" you are getting so that when you formulate a recipe, you know how much grain to use to obtain a certain gravity level.

Quote:

Originally Posted by RMitch (Post 2690315)
For example, my current batch yielded me about 53% efficiency, but a 1.060 post-boil OG. Had I upped my efficiency to the level it is supposed to be, (i.e. larger volume of sparge water), I'd most likely be starting with a 1.030 or lower OG, which wouldn't make for a good big beer, IMO.

No.. if you up your efficiency, then you end up with a higher OG at the end of the day, because upping yor efficiency means you managed to get more sugar out of the grain.

Quote:

Originally Posted by RMitch (Post 2690315)
Am I just completely confused, or is it impossible to have high efficiency with a big beer?

I do think you are a bit confused, but ... no.. it's not impossible to have high efficiency with a big beer.

RMitch 02-28-2011 07:16 PM

Ahh, well maybe I was using an erroneous efficiency calculator then. It basically seemed like as the efficiency went up, the gravity went down, as the wort was basically getting "watered down".

For example...at 5gal of collected runnings, I was at 53%, but if I sparged an additional 4galls, it would bring me up to 85% or so. But it seems to me like the more one sparges, the more diluted the wort will be, as you are ultimately using the same amount of grain. Maybe that is where I am mistaken.

motobrewer 02-28-2011 07:19 PM

i'm in the same situation. i have great mash efficiency but what i end up with in the fermentor is much lower. i always end up topping off with water, and i think i've been leaving too much being in the kettle.


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