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Old 11-11-2012, 07:05 PM   #1
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Default Need help determining what my intended mash OG should be

I'm curious how many gravity points are being contributed to my wort by the grain before I add DME and more water and start boiling.

Assuming, 9 liters of water (1.5 L/1 lb. grain) and about 149-150 F mash temperature, what is the OG of a mash sample for the following:

4 lbs. American 2-row
22 oz. American Wheat malt
10 oz. Franco-Belges Caramel Pils 10L

(6 lbs. total grain)

This is a BIAB partial mash.

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Old 11-11-2012, 07:26 PM   #2
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It depends on your efficiency. In my system (not a BIAB), I'd get 1.066 with 9 liters out of that mash. But you won't get 9 liters out if you put 9 liters in, asd the grain will absorb some of the liquid.

You'd have to check the OG (cool the sample first if you're using a hydrometer!), and then add the appropriate amount of DME and/or water to get to your desired OG.

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Old 11-12-2012, 04:41 AM   #3
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If you are talking Conversion Efficiency (SG of MLT liquor), use this chart: http://www.braukaiser.com/wiki/index...rt_gravity.gif

This will tell you what your first wort gravity should be based on your mash thickness. Using this you know your conversion so any drops in efficiency are not related to your grain conversion.

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Old 11-13-2012, 01:14 PM   #4
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Quote:
Originally Posted by Yooper View Post
It depends on your efficiency. In my system (not a BIAB), I'd get 1.066 with 9 liters out of that mash. But you won't get 9 liters out if you put 9 liters in, asd the grain will absorb some of the liquid.

You'd have to check the OG (cool the sample first if you're using a hydrometer!), and then add the appropriate amount of DME and/or water to get to your desired OG.
This is a partial mash brew that I made with leftover grain. I'm just trying to determine how much gravity was contributed by that grain to the mash.

Promash & Hopville also determined approx. 1.066 OG from the 9 liter mash (and 1.070 OG total for my 7 gallon batch after the boil + DME/sugar). However, the hydrometer sample that I took of the 9L mash after 60 minutes read 1.050 OG (cooled only slightly to about 100 F keep in mind).

My boil volume was 9 gallons, so when the additional 6.6 gallons of water was added, this dropped the mash OG to about 1.024 before the DME and sugars were added. Though I finished as projected at 1.070 OG (read at 70 F) without adding to the originally intended amounts of DME and sugar.

How did I hit my end numbers when my mash efficiency was much lower than expected without adding more DME/sugar to the original recipe to account for that huge difference?
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Old 11-13-2012, 04:32 PM   #5
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Like others have mentioned your estimated OG in all-grain depends on your efficiency, in other words, how much of the potential sugar in the grains were you able to convert and get into your boil kettle.

One thing you have do is to work backwards. What was your gravity and volume going into the fermenter? If I'm reading correctly it was 7 gallons with a 1.070 OG.

The gravity contribution of extracts and sugars don't depend on efficiency. We can back those ingredients out from totals and determine your OG and partial mash efficiency.

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Old 11-13-2012, 04:44 PM   #6
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1.070 OG at 7 gallons = 490 total gravity points (70 ppg x 7 gallons)

DME contributes about 40 points per gallon (ppg) and dextrose is about 46 ppg.

DME 4 pounds = 160 gravity points (gp)
DME 3 lbs. 5 ounces = 120 gp + (5/16 x 40 = 12.5) = 132.5 gp
Dextrose 1 lbs. 6 ounces = 46 + (6/16 x 46 = 17.25) = 63.25 gp

Extracts and dextrose = 160 + 132.5 + 63.25 = 355.75 gravity points

So, the partial mash must have contributed about: 490 - 355.75 = 134.25 gravity points

You mashed with about 2.4 gallons (9 liters) then added 6.6 gallons to reach 9 gallons, but you're not accounting for the amount of liquid soaked up by the grains. Also, did you adjust the hydrometer sample? 1.050 at 100 degrees is actually 1.055 with the correction factor.

I'm estimating that grain absorption was about .15 gallons, so 2.4-.15 = 2.25 gallons after the mash. If your actual OG was 1.055 with 2.25 gallons, that's 55 x 2.25 = 123.75 gravity points from the mash. That's pretty close to the 134.25 estimate. The ppg calculation of DME and dextrose are estimates, actual values may differ slightly, plus if your volumes are off that too changes the calculations. I hope this helps, it was a lot of math to calculate

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Old 11-14-2012, 05:54 PM   #7
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Quote:
Originally Posted by Pie_Man View Post
If I'm reading correctly it was 7 gallons with a 1.070 OG.
Correct - probably more like 1.069.

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Originally Posted by Pie_Man View Post
DME contributes about 40 points per gallon (ppg) and dextrose is about 46 ppg.
My DME contribues 37 ppg, of which 4 lbs. were used early, 3 lbs. 5 ounces used at FO.

DME 4 pounds = 148 gp
DME 3 lbs. 5 ounces = 111 gp + (5/16 x 37 = 11.56) = 122.56 gp
Dextrose 1 lbs. 6 ounces = 46 + (6/16 x 46 = 17.25) = 63.25 gp

Extracts and dextrose = 148 + 122.56 + 63.25 = 333.81 gravity points

So, the partial mash must have contributed about: 490 - 333.81 = 156.19 gravity points

Quote:
Originally Posted by Pie_Man View Post
You mashed with about 2.4 gallons (9 liters) then added 6.6 gallons to reach 9 gallons, but you're not accounting for the amount of liquid soaked up by the grains. Also, did you adjust the hydrometer sample? 1.050 at 100 degrees is actually 1.055 with the correction factor.
Correct. Did not adjust. The mash hydrometer sample was quite hot at approx. 110-115 F. I only let it cool down partially and I neglected to adjust the 1.050 reading directly sampled from the 9 Liter mash.

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I'm estimating that grain absorption was about .15 gallons.
Grain absorption was probably a little bit more than .15/g. I do not squeeze the grain bag. I let it hang drip dry, rinse the grain bag thoroughly, let drain more, and then toss it. Did not measure the collected volume after the mash though. I simply added it to the main water volume, brought to a boil, and added a portion of the DME at 60.

Thanks for doing the math. It's something I suck at. So with more information, what is the conclusion here? I just want to make sure my mash efficiency is not like 58% or something. Like I said, I did not add more DME/sugar than the recipe originally intended and I still hit my target gravity per the calculator, which was read 1.069/1.070 at 68 F via a hydrometer.
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Old 11-14-2012, 06:50 PM   #8
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The Braukeiser table only tells you the SG of the first few drops of runnings. Its like going to the pub and choosing between 4 pints of 8% ABV beer or 8 pints of 4% ABV beer. I would be interested to know if diluting the mash affects how much fermentable sugars you can get from the pale malt.

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Old 11-14-2012, 07:08 PM   #9
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The mash isn't diluted. It's full concentration and part of the intended recipe. That wort is then gathered from the mash and used in tandem with DME, sugar, and more water via a partial mash, full volume boil.

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Old 11-14-2012, 08:01 PM   #10
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Quote:
Originally Posted by EyePeeA View Post
So, the partial mash must have contributed about: 490 - 333.81 = 156.19 gravity points
Calculating efficiency is the sugars extracted from the grain divided by the potential amount of sugars in the grain * 100:
In other words: (Sugars extracted / Sugar potential) * 100

Sugars extracted is easy to calculate: volume of wort * (OG - 1.000)

Sugar potential depends on the grain, most base malts are about 1.036, meaning at 100% efficiency 36 gp would be extracted. So, the potential of each of your grains multiplied by the weight of the grains used.

Sugars extracted = 1.050 gravity sample at 110 degrees is 1.057 with the correction factor. You said you think the absorption was more than .15, maybe .25 gallons.
So, 2.4 gallons - .25 gallons = 2.15 total gallons: 2.15 * 57 = 122.55 gravity points extracted (sugars extracted)

Sugar potential, I usually rely on beersmith for this, but I'll give it a try. I'll estimate 36 points for the 2 row, 38 for the wheat malt, and 34 for the 10L crystal malt. source: Designing Great Beers by Ray Daniels
2 row = 36 * 4 = 144
Wheat = 38 + (6/16 * 38) = 52.25
10L Crystal = (11/16 * 34) = 23.275
Sugar Potential = 144 + 52.25 + 23.275 = about 219.53
Efficiency = 122.55 / 219.53 * 100 = about 56%

Some general observations:
1. I'm not sure your mash OG is accurate. You don't know the exact temperature for the hydrometer correction factor and you don't know the exact volume. In the future, take the sample cool it in the fridge, not the gravity, then you can return the sample to the boil.
2. There's a discrepancy between your actual gravity reading and what our calculations predicted your partial mash gravity to be, 156.19 vs 122.55. In my opinion, this is probably because your volumes are off and/or your hydrometer is off.
3. Don't be discouraged by the low efficiency. Keep brewing and take very good notes during the brew process. I make a checklist before I brew and write down my notes next to the checklist item. That's helped me improve my process. Also, find a way to approximate your volumes (a long spoon with markings, etc.)

I hope this helps. PS - Buy brewing software
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