Author Topic: Original Gravity  (Read 770 times)

Offline Chad G

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Original Gravity
« on: August 21, 2021, 08:39:24 pm »
I missed my original gravity for my first ever brew, by like 8 points. I was aiming for 1.042 and got 1.034. 1) How do I correct, if possible, my gravity? (I JUST pitched) 2) I mashed for 40 min at 152. Should I have mashed longer? Did I maybe use too much water? (3.75 gallons for 2.5 gallon batch) Brewfather said I had enough grains in my recipe. So I’m not sure if it’s my grains?

Offline majorvices

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Re: Original Gravity
« Reply #1 on: August 22, 2021, 05:10:43 am »
The biggest overall factor on your mash efficiency is probably your crush. You probably should start with a 1mm gap and tighten it up form there until you get the efficiency you want.

Make sure your hydrometer is calibrated correctly. I have seen them off by as much as 6 points (the paper sometimes shifts if dropped, etc). Just measure it in water. It should read 1.000 -- if not add or minus accordingly.

Other than that, don't overlook something simple like leaving out a portion of grain or your scale being off or the homebrew shop shorting you, etc.


Offline tommymorris

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Original Gravity
« Reply #2 on: August 22, 2021, 05:18:59 am »
I missed my original gravity for my first ever brew, by like 8 points. I was aiming for 1.042 and got 1.034. 1) How do I correct, if possible, my gravity? (I JUST pitched) 2) I mashed for 40 min at 152. Should I have mashed longer? Did I maybe use too much water? (3.75 gallons for 2.5 gallon batch) Brewfather said I had enough grains in my recipe. So I’m not sure if it’s my grains?
Your question about using too much water is also quite relevant. You need to measure the volume of beer after boil. Having too much volume after boil leads to diluted wort (lower specific gravity).

You need to know the volume before and after boil to calculate your boil off rate.  That will allow you to calculate the correct water volumes to add for mash and sparge and ultimately lead to the correct volume after boil.

PS. You can add dry malt extract to your fermenter to get the gravity up to your target. But 1034 will make a small beer but probably a good beer. So, I would just leave this batch alone.
« Last Edit: August 22, 2021, 05:21:16 am by tommymorris »

Offline KellerBrauer

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Re: Original Gravity
« Reply #3 on: August 22, 2021, 07:00:02 am »
Another point I would like to add to the great advice above is to check your calculations.  Are you using software to calculate, are you doing it manually, or maybe a recommended recipe?  Did you compensate for temperature when measuring the SG?  Did you check and adjust the pH?  Many factors are at play when brewing all-grain beer.
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Offline Saccharomyces

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Re: Original Gravity
« Reply #4 on: August 22, 2021, 07:04:14 am »
Welcome to the hobby.  All-grain is a lot to bite off for a first beer.   It is not unusual to achieve a lower than desired extraction rate when starting out with all-grain.  It looks easy, but there is a technique to it.  When I started to brew, no one started out with all-grain.  The normal transition was can and kilo kit beers -> extract recipes-> partial mash -> all-grain.  The partial mash step was critical for me, as it allowed me to learn how to crush, mash, and lauter correctly while having the bulk of the extract come dry or liquid malt extract.

How are you lautering?  A forty-minute saccharification rest is pretty short.  Crush is critical with a rest that short.  I rest for ninety minutes.  The basic conversion is over in under an hour, but I achieve a better extraction rate and the beer tastes better with the longer rest.  I also continuous sparge, so I am usually not in a hurry when I brew.  Your mileage my vary.
« Last Edit: August 22, 2021, 07:05:48 am by Saccharomyces »

Offline Steve Ruch

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Re: Original Gravity
« Reply #5 on: August 22, 2021, 09:11:26 am »

How are you lautering?  A forty-minute saccharification rest is pretty short.  Crush is critical with a rest that short.  I rest for ninety minutes.  The basic conversion is over in under an hour, but I achieve a better extraction rate and the beer tastes better with the longer rest.  I also continuous sparge, so I am usually not in a hurry when I brew.  Your mileage my vary.
Since most saccharification is done in the first 20 minutes or so it's unlikely that a 40 minute mash would be that short on O G. Many years ago I went from 60 to 45 minutes with no difference in O G.
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Offline denny

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Re: Original Gravity
« Reply #6 on: August 22, 2021, 09:55:34 am »
Welcome to the hobby.  All-grain is a lot to bite off for a first beer.   It is not unusual to achieve a lower than desired extraction rate when starting out with all-grain.  It looks easy, but there is a technique to it.  When I started to brew, no one started out with all-grain.  The normal transition was can and kilo kit beers -> extract recipes-> partial mash -> all-grain.  The partial mash step was critical for me, as it allowed me to learn how to crush, mash, and lauter correctly while having the bulk of the extract come dry or liquid malt extract.

How are you lautering?  A forty-minute saccharification rest is pretty short.  Crush is critical with a rest that short.  I rest for ninety minutes.  The basic conversion is over in under an hour, but I achieve a better extraction rate and the beer tastes better with the longer rest.  I also continuous sparge, so I am usually not in a hurry when I brew.  Your mileage my vary.

In researching the last book, I did a number of 20 min. mashes.  I averaged 75+ % efficiency.
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Offline BrewBama

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Original Gravity
« Reply #7 on: August 22, 2021, 12:13:28 pm »
You may also consider the pH of the mash. The enzymes that convert starch to sugars have a pH range they operate best within. I realize this is your first brew but it is something to consider as you progress.

As you progress you will begin to see trends and then can make adjustments. It could be that given your water, mill setting, equipment, processes, etc yield a slightly less efficient output than the brewer who wrote the recipe you’ve used. When you do have some consistent results under your belt you can make confident adjustments to meet your expectations. I rarely use recipes as written to meet a certain OG. There’s usually a slight increase/decrease to reach their spec when using my brewery.

As far a mash time:

Over a series of half a dozen + brews days, using the same ~12#  grist, milled at the same ~.040 gap, 1.75:1 water ratio, 5.5 gal strike, 3 gal batch sparge volumes, mineral additions, recirculation pump flow setting, etc, I took samples at 20 minute intervals throughout the entire mash. I noticed very little pH change over the entire mash ...like +/- .03 cooled to room temp (actual data from one of those brewdays below), which is well within the margin of error given the MW101 pH meter and loose nut between the chair and meter.

When graphed, the data from that series overlaid upon each other are nearly indistinguishable one from another. Very consistent results.

Over that series, I noticed most of the SG increase takes place within 20 min. @152*F. ...but I measured additional SG increase to about the 100 min mark. Past the 100 min mark the SG did rise but very very little.

20 min 1.045, 5.47 pH, 65% of OG
40 min 1.056, 5.47 pH, + 11 points, 81% of OG (+16%)
60 min 1.060, 5.50 pH, + 4 points, 86% of OG (+5%)
80 min 1.065, 5.44 pH, + 5 points, 94% of OG (+8%)
90 min 1.069, 5.46 pH, + 4 points, (+6%)


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« Last Edit: August 22, 2021, 12:38:46 pm by BrewBama »

Offline Saccharomyces

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Re: Original Gravity
« Reply #8 on: August 22, 2021, 12:58:06 pm »
I also noticed an increased extraction rate with a 90-minute rest.  At 45 minutes, I averaged 27 points per pound.   At 90 minutes, my extraction rate runs in the 29 to 30 points per pound range (efficiency of 80 to 83%).  I started out with a 60-minute rest, went down to a 45-minute rest before going to a 90-minute rest.   I started doing the 90-minute rest because it gave me more time heat my sparge water and do other brewing-related tasks without feeling rushed.  Up until I built current brewery, I mashed in my kitchen and boiled outside or in my garage, which meant heating strike and sparge water on a kitchen stove.  Over time, I realized that I liked the finished product more with a 90-minute rest and a 90-minute boil.  Sure, a long rest combined with a long boil leads to a longer brew day, but I only brew one batch a month at most.  The longer boil gives me time to clean everything, but my kettle.  I brew like I cook in that I clean as I go.  Cooks who pile everything up until they are done cooking drive me crazy.

Offline BrewBama

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Original Gravity
« Reply #9 on: August 22, 2021, 03:11:22 pm »
I also noticed an increased extraction rate with a 90-minute rest.  At 45 minutes, I averaged 27 points per pound.   At 90 minutes, my extraction rate runs in the 29 to 30 points per pound range (efficiency of 80 to 83%). …

+1. I settled on 60 min for the main mash as a balance between fermentability and OG then add dark grains for a 15 mash out/hot steep, then lauter, then another 15 min recirculation/hot steep after batch sparge. Total 90 min.



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« Last Edit: August 25, 2021, 06:44:18 am by BrewBama »

Offline chinaski

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Re: Original Gravity
« Reply #10 on: August 22, 2021, 06:06:14 pm »
A lot of information of things to try here- which is great.  It's also not a bad idea to just let this first beer ferment, package it, and enjoy it as is!  The OG numbers won't tell you exactly what this beer will taste like, and taste is the most important thing.  If you can, note what the overall efficiency you got with this brew, and use that to adjust the next brew- you'll use more grain to get the gravity you expect and that's fine.  In the end, you want to be able to predict your OG reasonably well for each brew.  It doesn't matter what the efficiency is if it's consistent.

Congrats and welcome to brewing!

Offline Kevin

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Re: Original Gravity
« Reply #11 on: August 23, 2021, 07:37:20 am »
I aqree 100% with chinaski. Accept what you have. Learn from the experience. Make corrections in the next beer.
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Offline goose

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Re: Original Gravity
« Reply #12 on: August 23, 2021, 07:45:35 am »
One other thing you need to be aware of is the temperature you hydrometer is calibrated for and the temperature of the chilled wort.  Many hydrometers are calibrated at 60 degrees F. and you have to compensate for the difference in the temperature of the chilled wort and the calibration temperature.  Most of the hydrometers will have a calibration sheet with them so you can adjust for the temperature of you wort.

The better hydrometers will have an internal thermometer that will tell you how much to correct the reading (either + or -).  I do all of my readings in degrees Plato rather than SG and the hydrometers I have all have an internal thermometer.  Measuring in Plato is a throwback from my pro brewing days.
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Offline BrewNerd

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Re: Original Gravity
« Reply #13 on: September 02, 2021, 03:22:18 pm »
The OG numbers won't tell you exactly what this beer will taste like, and taste is the most important thing.

Superb observation.

For all the fretting about specialized equipment and decimal points, the Mk 1 tongue beats 'em all.