Efficiency question??

[Oldskewl]

Yesterday I brewed a NB Mustache Envy Belgian stout. NB stated the OG at 1.080. My pre boil Gravity was 1.056 and I hit 1.066 post boil using a BIAB method and squeezing the bag. I think I used to much mash water. Anyway when I calculate the potential gravity it came out to 1.116. When calculating efficiency that claims home brewing is in the 70-80% range, I assume this is based on the potential gravity not the OG predicted by the recipe?

 

[SteveHeff]

Was there any DME or LME that you possibly forgot to add? My numbers are usually superb when BIAB...and I don't do anything special to make that happen. I'll hit 75-82% regularly. Too much mash water will certainly knock that number down. How much mash water did you use?

 

[Gnomebrewer]

Yes, as a fairly rough estimate I'd say most brewers are in the 70% to 80% range (of potential gravity). There are many brewers that get much higher and many who get much lower (often in an effort to save time).

Predicted OG for a recipe is based on all of the extractable sugars in the given volume, multiplied by your estimated efficiency. It looks like the NB recipe you have is based on about 70% efficiency. You got about 57% efficiency (assuming your volume was the same as the recipe called for).

Too much mash water shouldn't affect efficiency that much - some brewers successfully brew with all of their water in the mash (no sparge) and get good efficiency. There are lots of threads detailing what to do to identify where your efficiency could be improved.

 

[doug293cz]

What were your malt bill, strike water volume and pre-boil volume. Need those in addition to your pre-boil SG to make sense of things.

Brew on

 

[Oldskewl]

This was my first 5 gal batch so I am still getting my processes down. Thanks for clearing that up! So a recipe such as the NB has already taken efficiency into account. Therefore I need to hone my processes and find out where I can improve. Here is the grain bill:
- 14.5 lbs Franco-Belges Pilsen Malt
- 0.5 lbs. Belgian Aromatic Malt
- 0.5 lbs. English Roasted Barley
- 0.25 lbs. Belgian Biscuit Malt
- 0.25 lbs. Weyermann Carafa III

Strike water volume was 8.5 gal and my pre boil was 7.5 gal. There was not any dime to be added to the recipe.

 

[soccerdad]

Did NB crush the grain for you?

 

[theseeker4]

This was my first 5 gal batch so I am still getting my processes down. Thanks for clearing that up! So a recipe such as the NB has already taken efficiency into account. Therefore I need to hone my processes and find out where I can improve. Here is the grain bill:
- 14.5 lbs Franco-Belges Pilsen Malt
- 0.5 lbs. Belgian Aromatic Malt
- 0.5 lbs. English Roasted Barley
- 0.25 lbs. Belgian Biscuit Malt
- 0.25 lbs. Weyermann Carafa III

Strike water volume was 8.5 gal and my pre boil was 7.5 gal. There was not any dime to be added to the recipe.

So your pre-boil gravity was 7.5 gallons at 1.056, this would give you 420 points of gravity total, which would put you at 1.084 OG if you had 5 gallons after your boil. Looks like you post-boil volume was 6.4 gallons or so to get you an OG of 1.066. It looks like your efficiency was fine, but you ended up with too much water/not enough boil off. Either that, or your gravity and/or volume measurements are off somewhere.

For future brews; you lost about 1.1 gallons of water from your pre-boil to your post boil volume, so that was your boil off amount, and you had a grain absorption of about 0.0625 gallons per pound of grain. Next time you brew, keep everything the same, but calculate your strike volume by:
target volume (5 gallons) + boil off (1.1 gallons) + grain absorption (0.0625 x grain bill in pounds) + losses from trub, etc. = strike water volume

Obviously, if you want to actually have 5.5 gallons in the fermentor, you would put that number in instead of 5 gallons.

Good luck!

 

[Oldskewl]

Yes I did have NB crush the grain. I mashed an extra 15 minutes to make sure I had conversion and verified with an iodine test. I have not invested in a mill yet. I hope to next year.

Thanks for the explanation theseeker4. I was targeting 6 gal post boil allowing for 0.5 gal trub and 5.5 gal going into fermenter. I squeezed the bag pretty well and allowed the bag to drain during the whole 60 minute boil. It's hard to believe my grain absorption was that high. Is it ok to continue to boil another half gallon off after your finished your hop additions?

 

[Gavin C]

Yes I did have NB crush the grain. I mashed an extra 15 minutes to make sure I had conversion and verified with an iodine test. I have not invested in a mill yet. I hope to next year.

Thanks for the explanation theseeker4. I was targeting 6 gal post boil allowing for 0.5 gal trub and 5.5 gal going into fermenter. I squeezed the bag pretty well and allowed the bag to drain during the whole 60 minute boil. It's hard to believe my grain absorption was that high. Is it ok to continue to boil another half gallon off after your finished your hop additions?

No don't do that as any late hop additions will become bitteringa dditions.

if you need to make boil-length adjustments do them prior to any hop additions.

I would not leave the grain sitting over the boil for that long. You're steaming the grain potentially leaching out undesirable stuff.

Also it will reduce your boil-off and potentially capture unwanted DMS.

Just ideas. I've no concrete evidence to show this occurs.

That is a lot of sugar you are leaving behind in the kettle at 0.5 gallons. I would not do that.

 

[MonkeyBot]

Yes I did have NB crush the grain. I mashed an extra 15 minutes to make sure I had conversion and verified with an iodine test. I have not invested in a mill yet. I hope to next year.

Thanks for the explanation theseeker4. I was targeting 6 gal post boil allowing for 0.5 gal trub and 5.5 gal going into fermenter. I squeezed the bag pretty well and allowed the bag to drain during the whole 60 minute boil. It's hard to believe my grain absorption was that high. Is it ok to continue to boil another half gallon off after your finished your hop additions?

You generally don't want to boil the hops more than the recipe states. The longer you boil the hops, in general, the more bitterness you get and the less flavor/aroma you get. Volatile oils responsible for the flavors and aromas vaporize during the boil and you get higher alpha acid isomerization with a longer boil. The alpha acids in hops isomerizing are what give the beer the bitterness. So any late additions to the boil will lose their flavor and aroma and add more bitterness to the beer which will make it taste like a different beer.

Just consider this a learning experience. Your beer is going to be a bit weaker than the intended brew but should probably still be tasty. You gained some important information from this brew, namely your boil-off rate. Use that and the information theseeker4 gave you to hit your targets better next time!

 

[doug293cz]

So your pre-boil gravity was 7.5 gallons at 1.056, this would give you 420 points of gravity total, which would put you at 1.084 OG if you had 5 gallons after your boil. Looks like you post-boil volume was 6.4 gallons or so to get you an OG of 1.066. It looks like your efficiency was fine, but you ended up with too much water/not enough boil off. Either that, or your gravity and/or volume measurements are off somewhere.

For future brews; you lost about 1.1 gallons of water from your pre-boil to your post boil volume, so that was your boil off amount, and you had a grain absorption of about 0.0625 gallons per pound of grain. Next time you brew, keep everything the same, but calculate your strike volume by:
target volume (5 gallons) + boil off (1.1 gallons) + grain absorption (0.0625 x grain bill in pounds) + losses from trub, etc. = strike water volume

Obviously, if you want to actually have 5.5 gallons in the fermentor, you would put that number in instead of 5 gallons.

Good luck!

Good analysis, but leaves out a correction for the thermal expansion of the wort. Assuming you measured your strike water at room temp (68° - 70°F), and pre-boil volume at mash temp (~150°F), then the temp corrected pre-boil volume would be 7.5 gal * 0.982 = 7.37 gal. This puts your grain absorption at (8.5 -7.37) / 16 = 0.071 gal/lb. This isn't bad, but can be decreased by more aggressive bag squeezing.

A no-sparge lauter with your volumes and grain bill will have an efficiency of about 78%. This can be increased a little by reducing your grain absorption. Your overall mash efficiency was 72.6% - 72.7%, which puts your conversion efficiency at about 93%. This is not bad, but can be increased to the 95% - 99% range with a finer crush and/or longer mash time.

Your iodine test didn't detect residual starch because it was most likely trapped in the center of the grits, and not exposed to the iodine. To get a more accurate result, you should include some grain in the test sample, and crush included grain to expose any starch.

I get your room temp post-boil volume at 7.37 * 56 / 66 = 6.25 gal, for a boil-off of 1.12 gal.

So, as @theseeker4 said, your low OG is totally explained by the excess volumes.

Brew on

 

[Oldskewl]

Thanks for all the input. I have definitely learned a lot. I used the BIAB calculator to estimate my strike volume and temp. It looks like I over shot the strike volume by about 1/2 to 3/4 of gallon. You guys must squeeze the living crap out of your bags to get under 0.04 gal/lb. I felt I did pretty good, but apparently not. I may have to pick up a basket to aid in the squeezing process.

 

[doug293cz]

Thanks for all the input. I have definitely learned a lot. I used the BIAB calculator to estimate my strike volume and temp. It looks like I over shot the strike volume by about 1/2 to 3/4 of gallon. You guys must squeeze the living crap out of your bags to get under 0.04 gal/lb. I felt I did pretty good, but apparently not. I may have to pick up a basket to aid in the squeezing process.

Very few BIAB'ers get under 0.04 gal/lb. If you get to 0.06 gal/lb, you are doing a pretty good job. Some of the folks claiming under 0.04 gal/lb may have measurement or calculation issues.

Brew on

 

[AnthonyUK]

You shouldn't expect the same efficiency across all gravities as it isn't linear.
For a 1.080 OG I would expect something in the 55-65% range using BIAB.

 

[doug293cz]

You shouldn't expect the same efficiency across all gravities as it isn't linear.
For a 1.080 OG I would expect something in the 55-65% range using BIAB.

I think you are overly pessimistic about efficiency obtainable on high gravity beers using BIAB. To get the efficiencies you state, you need a combination of poor mash conversion and higher than desirable grain absorption.

Lauter efficiency for a constant pre-boil volume goes down as the grain bill increases for two reasons:

1. The grain to water ratio increases making for more concentrated wort. Thus the wort remaining in the grain contains more sugar.
2. With more grain, the total grain absorption increases, thus the grain retains a larger percentage of the sugar.

You can compensate for these somewhat by increasing the pre-boil volume, but then you have to boil longer to get the same post-boil volume.

A third factor can also come into play. Thicker mashes often have reduced conversion efficiency due to slower conversion rates.

Here's a chart that shows what happens to lauter efficiency for both full volume (no sparge) and equal volume batch sparge as a function of grain bill weight for a fixed pre-boil volume of 6.7 gal, and various grain absorption rates.



With full volume (no sparge) BIAB, a grain absorption of 0.060 gal/lb (aggressive squeezing), 17 lbs of grain, and 6.7 gal pre-boil, it is possible to bet a 1.080 OG and 72.9% mash efficiency. To do this you need a good mash with a conversion efficiency of 95%. You could hit 1.080 with 19 lbs of grain and no squeezing (0.10 gal/lb grain absorption) for a mash efficiency of 65%. A batch sparge process would have even higher efficiency.

Brew on

 

[AnthonyUK]

Other things to consider though, is increasing mash efficiency making better beer and increasing pre-boil volume only to have to boil it off is not efficient in both time or money.
I don't tend to make many beers of this gravity using BIAB but have tended to achieve towards the higher end of my estimates without too much effort as I'm pretty certain I have my mashing process dialed in on my system.