Author Topic: Raising gravity in all-grain batches  (Read 1059 times)

Offline dwags66

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Raising gravity in all-grain batches
« on: June 22, 2014, 09:54:14 AM »
Hey everyone! First post of all time, appreciate the insight and feedback yet to come.
Basics: 2 batches of all-grain under my belt (stout & pale) and both have come out with relatively low OG & FG, yielding 3.5-4.5% ABV.
Before all of the comments about "flavor not alcohol", I'm more interested in techniques and control rather than getting a drunk on. 
My assumption is equipment + tech. can produce higher OG's and some fuller bodied beers rather than just upping the grain bill.  I can supply specifics if that's helpful, but most interested in general guidelines.
Cheers!

Offline Jimmy K

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Re: Raising gravity in all-grain batches
« Reply #1 on: June 22, 2014, 10:08:38 AM »
What OG and FG are you getting and what were you expecting? If it's just a few points it's not much to worry about. If it's significant, maybe there is something to change.

Specifics are always helpful. We could spout generalities all day but it may not apply to you. What sort of sparging are you doing and what is your grain bill? I'd assume your grain is crushed by the homebrew shop?
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Offline philm63

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Re: Raising gravity in all-grain batches
« Reply #2 on: June 22, 2014, 10:09:39 AM »
Specifics would really help, but a couple of things come to mind readily; crush, and volumes. Do you crush your own grain, or does your LHBS crush it for you? How confident are you that your volumes are accurate/correct? Do you use a brewing calculator or a program such as BeerSmith?
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Offline dwags66

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Re: Raising gravity in all-grain batches
« Reply #3 on: June 22, 2014, 10:25:40 AM »
Stout recipe was full on LHBS, so grain, crush, and volumes supplied by them. When I'm home from work tonight I'll get into my binder and check numbers.

Pale was my first shot at a SMaSH, and went off of forum ideas to get:
11lbs 2-row pale (I think NorthWestern?) and crushed at LHBS.
Threw in 1lb 15L that I had for some color. 
WLP001.
Used a calculator for mash & sparge volumes. 
OG - 1.038, FG at bottling - 1.010.
I know that I struggled with mash tun temp, was in the 140's rather than 150's.
Topped off .5 gal after boil. Maybe partial explanation?
Bottling flavor = excellent, just thin.
Thx

Offline santoch

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Re: Raising gravity in all-grain batches
« Reply #4 on: June 22, 2014, 11:08:17 AM »
1.038 out of a 12 lb grain bill for 5 gallons is pretty low.  at 70% efficiency you should be seeing roughly 1.060. 

What was your exact final volume?  If you ended with 7 gallons instead of five,
1.060 *  5/7 ~= 1.042, which is in the ballpark if you are sending 6 to your fermenter and you still pull out a gallon of hops and trub.

1) More specifics - Batch sparge?  If so, how many rinses?
2) Fly sparge? how fast?
3) Other technique like BIAB?  Did you sparge at all?


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Offline GBRewed

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Re: Raising gravity in all-grain batches
« Reply #5 on: June 22, 2014, 11:30:54 AM »
Exact final volume would be pretty helpful.  Also what kind of mash tun are you using?  Is it insulated or is there a chance the temperature changed drastically during the mash?  How long was your mash?

Offline dwags66

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Re: Raising gravity in all-grain batches
« Reply #6 on: June 22, 2014, 12:28:17 PM »
Exact final volume would be pretty helpful.  Also what kind of mash tun are you using?  Is it insulated or is there a chance the temperature changed drastically during the mash?  How long was your mash?
Doing the cooler thing, and though I did a hot water rinse before mashing, I'm sure it wasn't fully effective because I boiled to the low 160's, and easily lost 15degs...

As to the pre-boil volume, I did come out with approx. 6.5gal...

Offline klickitat jim

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Re: Raising gravity in all-grain batches
« Reply #7 on: June 22, 2014, 12:37:24 PM »
How long are you mashing? How many quarts per pound?

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Re: Raising gravity in all-grain batches
« Reply #8 on: June 22, 2014, 01:37:25 PM »
2) Fly sparge? how fast?

Mash tun geometry and mash filter design are more critical than flow rate when continuous sparging.  If the hot liquor is flowing through the mash bed evenly, then the delta between a slow sparge and a moderate speed sparge is not huge.
« Last Edit: June 22, 2014, 04:27:18 PM by S. cerevisiae »

Offline HoosierBrew

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Re: Raising gravity in all-grain batches
« Reply #9 on: June 22, 2014, 03:47:36 PM »

Doing the cooler thing, and though I did a hot water rinse before mashing, I'm sure it wasn't fully effective because I boiled to the low 160's, and easily lost 15degs...



Sounds like, among other things, you didn't account for the temp drop of adding room temp malt to your strike water. All the good brewing software versions have strike temp calculators, which help you account for this temp drop. Brewer's Friend,  Beersmith, and ProMash all do a fine job (assuming you're not using one).                                                                                                                                                                                                      One of the first obstacles in AG brewing is in learning your system - measuring mash and sparge volumes accurately, learning your dead space, accounting for grain absorption, collecting accurate pre and post boil volumes, measuring temp and gravities accurately. That's a lot of stuff. After you spend time tightening up each of these variables, the rest will fall into place.
« Last Edit: June 22, 2014, 04:57:47 PM by HoosierBrew »
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Re: Raising gravity in all-grain batches
« Reply #10 on: June 22, 2014, 07:01:10 PM »
If you are mashing at around 1.25 quarts of water (strike liquor) per pound in a typical cooler setup, a quick rule of thumb is to mash-in with strike liquor that is approximately nineteen to twenty degrees Fahrenheit higher than the desired rest temperature. For example, with a strike liquor to grist ratio of 1.25 quarts for pound, mashing-in with 170F strike liquor should result in the mash coming to rest at around 150F to 151F.

Here's the math:

Twenty pounds of grain has approximately as much heat capacity (a.k.a. specific heat) as one gallon of water; therefore, a pound of grain has approximately as much heat capacity as 0.05 gallons of water (1 / 20 = 0.05) or 0.2 quarts of water (1 / 20 x 4 = 0.2).

strike_liquor_temperature = ((desired_strike_temperature x (0.2 x grist_weight_in_pounds + strike_liquor_volume_in_quarts)) - (0.2 x grist_weight_in_pounds x grist_temperature)) / strike_liquor_volume_in_quarts

What the equation shown above does is calculate the total specific heat of the mash with respect to N  quarts of water.  This value includes the specific heat of the grain at rest temperature.  The pre-mash-in grain specific heat is subtracted from the total mash specific heat, and the difference is then divided by the strike liquor volume in quarts yielding the strike liquor temperature.  The equation can be simplified to:

strike_liquor_temperature = (total_mash_specific_heat – grain_specific_heat_before_mash_in) / strike_liquor_volume_in_quarts

where

total_mash_specific_heat = desired_strike_temperature x (0.2 x grist_weight_in_pounds + strike_liquor_volume_in_quarts)

grain_specific_heat_before_mash_in = 0.2 x grist_weight_in_pounds x grist_temperature

Example:

grist_weight_in_pounds = 10
grist_temperature = 72
strike_liquor_volume_in_gallons = 12.125 (1.25 quarts per pound)
desired_strike_temperature = 151F

total_mash_specific_heat = 151 x (0.2 x 10 + 12.5) = 2189.5

grain_specific_heat_at_mash_in = (0.2 x 10 x 72) = 144

strike_liquor_temperature = (2189.5 - 144) / 12.5 = 163.64F

In practice, depending on how full your mash tun is after mash-in has been completed, it will take an additional 4 to 6 degree increase in the strike liquor temperature to hit your target mash temperature due to thermal losses to the cooler itself, which is why a good strike liquor temperature for a 151F mash is around 170F when using a hot liquor to grist ratio of 1.25 quarts per pound in a non-preheated cooler-based mash tun.

The equation shown below is mathematically derived from the equation shown above. It is based on a strike liquor volume to one pound of grist ratio. This ratio holds as we increase the weight of the grist; therefore, the result holds as we scale the grist.

strike_liquor_temperature = (.2 / hot_liquor_to_grist_ratio_in_quarts_per_pound) x (desired_strike_temperature - grist_temperature) + desired_strike_temperature

grist_temperature = 72
hot_liquor_to_grist_ration_in_quarts_per_pound = 1.25
desired_strike_temperature = 151F

strike_liquor_temperature = (.2 / 1.25) x (151 - 72) + 151 = 12.64 + 151 = 163.64F

The equation shown above is equivalent to the “Initial Infusion Equation” in John Palmer’s book.  I merely used more descriptive variable names.  John labels desired_mash_temperature “T2,” grain_temperature “T1,” and hot_liquor_to_grist_ratio_in_quarts_per_pound “r” in his equation.

http://www.howtobrew.com/section3/chapter16-3.html

John Palmer’s Initial Infusion Equation:
Strike Water Temperature Tw = (.2/r)(T2 - T1) + T2
where:
r = The ratio of water to grain in quarts per pound
T1 = The initial temperature (¡F) of the mash
T2 = The target temperature (¡F) of the mash
Tw = The actual temperature (¡F) of the infusion water

Let’s say that I was completely dumbfounded that the equation found in John’s book yielded the same answer as the more complex equation that I had been using for years.  It then dawned on me that the equations had to be related, which meant the equation in John’s book had to be a very clever simplification of the equation that I had been using.  I sat down with pencil and paper and performed the algebra necessary to transform the equation that I had been using into the one in John’s book.  Here’s the math for those who into mind numbing things:   :)

First off, we set grist_weight_in_pounds equal to 1, which allows us to rename strike_liquor_volume_in_quarts to hot_liquor_to_grist_ratio_in_quarts_per_pound because the strike liquor volume is for one pound of grain.

strike_liquor_temperature = (desired_strike_temperature x (0.2 x 1 + hot_liquor_to_grist_ratio_in_quarts_per_pound) - (0.2 x 1 x grain_temperature)) / hot_liquor_to_grist_ratio_in_quarts_per_pound

which simplifies to:

strike_liquor_temperature = (desired_strike_temperature x (0.2 + hot_liquor_to_grist_ratio_in_quarts_per_pound) - (0.2 x grain_temperature)) / hot_liquor_to_grist_ratio_in_quarts_per_pound

Next, we divide both terms in the expression (desired_strike_temperature x (0.2 + hot_liquor_to_grist_ratio_in_quarts_per_pound)) - (0.2 x grain_temperature))  by  hot_liquor_to_grist_ration_in_quart_per_pound, yielding:

strike_liquor_temperature = desired_strike_temperature x (0.2 + hot_liquor_to_grist_ratio_in_quarts_per_pound) / hot_liquor_to_grist_ratio_in_quarts_per_pound  - 0.2 x grain_temperature / hot_liquor_to_grist_ratio_in_quarts_per_pound

Multiplying desired_strike_temperature through the expression (0.2 + hot_liquor_to_grist_ratio_in_quarts_per_pound) yields:

strike_liquor_temperature = (0.2 x desired_strike_temperature +  desired_strike_temperature x hot_liquor_to_grist_ratio_in_quarts_per_pound) / hot_liquor_to_grist_ratio_in_quarts_per_pound  - 0.2 x grain_temperature / hot_liquor_to_grist_ratio_in_quarts_per_pound

Dividing each term in the expression (0.2 x desired_strike_temperature  +  desired_strike_temperature x hot_liquor_to_grist_ratio_in_quarts_per_pound) by hot_liquor_to_grist_ratio_in_quarts_per_pound yields:

strike_liquor_temperature = 0.2 x desired_strike_temperature  / hot_liquor_to_grist_ratio_in_quarts_per_pound +  desired_strike_temperature x hot_liquor_to_grist_ratio_in_quarts_per_pound / hot_liquor_to_grist_ratio_in_quarts_per_pound
  - 0.2 x grain_temperature / hot_liquor_to_grist_ratio_in_quarts_per_pound

Which reduces to:

strike_liquor_temperature = 0.2 x desired_strike_temperature  / hot_liquor_to_grist_ratio_in_quarts_per_pound  +  desired_strike_temperature - 0.2 x grain_temperature / hot_liquor_to_grist_ratio_in_quarts_per_pound

Reordering the terms leaves us very close to the final form:

strike_liquor_temperature = 0.2 x desired_strike_temperature  / hot_liquor_to_grist_ratio_in_quarts_per_pound  - 0.2 x grain_temperature / hot_liquor_to_grist_ratio_in_quarts_per_pound +  desired_strike_temperature

The expression 0.2 x desired_strike_temperature  / hot_liquor_to_grist_ratio_in_quarts_per_pound  - 0.2 x grain_temperature / hot_liquor_to_grist_ratio_in_quarts_per_pound + desired_strike_temperature can be reduced to (0.2 x desired_strike_temperature  - 0.2 x grain_temperature)  / hot_liquor_to_grist_ratio_in_quarts_per_pound, which, in turn, can be reduced to 0.2 x (desired_strike_temperature  - grain_temperature)  / hot_liquor_to_grist_ratio_in_quarts_per_pound + desired_strike_temperature, which yields the final equation:

strike_liquor_temperature =  0.2 x (desired_strike_temperature  - grain_temperature)  / hot_liquor_to_grist_ratio_in_quarts_per_pound +  desired_strike_temperature

which can be reordered to:

strike_liquor_temperature =  0.2 /  hot_liquor_to_grist_ratio_in_quarts_per_pound  x (desired_strike_temperature  - grain_temperature)  +  desired_strike_temperature

which is the equation in John's book

Like I said, the simplification is very clever.
« Last Edit: September 22, 2015, 11:20:11 AM by S. cerevisiae »

Offline reverseapachemaster

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Re: Raising gravity in all-grain batches
« Reply #11 on: June 23, 2014, 07:15:06 AM »
It's hard not to assume that you either are getting an awful crush from your LHBS or your gravity readings are very off. I doubt your hydrometer is off by two tenths. I also suspect some of your mash problems may be related to water but I would first deal with the milling problem. Is there another store you could buy from or another local homebrewer that would let you borrow a mill so you can test out if poor milling at your LHBS is the problem?

I know the whole pre-heating your mash tun thing is a piece of advice that was once mandated on a particularly large forum as something you had to do to make good beer (I don't know if that is still preached with equal vigor there) but it isn't a necessary step. It's more of the nonsense that became canon on that site because a couple people with high volumes of posts said so. You can just heat the mash water an additional few degrees to account for the heat loss into the cooler. Software will easily help you calculate the appropriate water temperatures.
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Offline HoosierBrew

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Re: Raising gravity in all-grain batches
« Reply #12 on: June 23, 2014, 07:43:41 AM »
+1 to looking at crush. Your LHBS will double crush your grain for you if you ask them. LHBS often don't crush grain as fine as we do at home and therefore your efficiency can suffer. I don't think it's the solution to your entire problem but it's a variable to rule out in your troubleshooting process.
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Re: Raising gravity in all-grain batches
« Reply #13 on: June 23, 2014, 08:09:37 AM »
I agree with some others on the crush.  Milling my own via the LHBS via their hand mill helped a lot.  Also, make sure you are stirring the crap out of it when you dough in and when you add your sparge water.  I saw a significant increase in efficiency when I spent more time stirring (during sparge) to ensure I was getting residual sugar in suspension. 
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Re: Raising gravity in all-grain batches
« Reply #14 on: June 23, 2014, 08:10:09 AM »
I am going to take a set of feeler gauges with me the next time that I visit my LHBS.  I want to see if there is any truth behind the widely-spaced roller claim.  I am willing to bet that most LHBS mills are set at 0.045" or less.  However, I am also willing to bet that the gap is not uniform across the rollers due to wear.