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I'm looking to understand malt bills a bit more. I'm currently reading "Malt - A Practical Guide from Field to Brewhouse" by John Mallet. I'm particularly interested in the section describing the process to calculate a malt bill to achieve a specific Degrees Plato gravity. While I enjoy creating recipes and whatever comes out at the end comes out at the end, I would like to be able to accurately create beer recipes to a specific target gravity, and thus to a more accurate ABV. In one of the first steps it includes the quote:

Next I calculate the total extract needed. By reviewing the ASBC tables we find that 12°P wort contains 32.45 pounds of extract per bbl.

I work in metric and converting that to metric isn't an issue, nor is scaling it to my brew size an issue. However, I am unable to find this reference table anywhere.

Can anyone provide me with a table which lists out a weight of extract per volume of wort to achieve a specific gravity or °P reading?

In either imperial, lbs per bbl, or metric, kg per HL, would be appreciated. I can make any necessary conversions myself.

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Pounds extract per barrel is actually quite straightforward to calculate. Here's my method:

  • First you begin with the density of water. Water is ~8.34 pounds per gallon (depending on the temperature). Therefore a barrel is 258.5 pounds (31 gal.).

  • You will need both °Plato and SG for the calculation, and it is sufficient to use the old rule of thumb 1°P = 1.004 SG (eg. 10°P = 1.040 SG, or 13°P = 1.052 SG, etc.).

  • Since SG is just the density relative to water, you already know how much a barrel of wort (or beer or anything) will weight at any given SG. You just multiply the weight of a barrel (or any volume) of water by the SG (e.g. one barrel of wort at 12°P will weigh: 258.5 lb. x 1.048 SG = 270.9 lb., using the numbers mentioned above).

  • Finally, pounds extract per barrel is as simple as multiplying the weight of a barrel of wort at your gravity (270.9 lb. at 1.048 SG) by °P expressed as a percentage (e.g. instead of multiplying by 12, you multiply by 0.12, which is the same as 12%). So, 270.9 lb. x 0.12 = 32.5 lb. extract per barrel (close enough if you ask me).

- Remember that, while you're using both Plato and SG for different parts of the calculation, they must equal one another.

-The Plato scale simply expresses the level of extract (or dissolved solids) in a solution as a percentage of the total weight of the solution. This is why this method works

-Why this isn't exactly the same as the tables? 1) For some reason the ASBC uses the weight of water at 32°F for their calculation; 2) The conversion from SG to plato is not exact (as mentioned in the other answer)

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  • Ah, thank you. That's actually incredibly easy using the metric system then as 1L = 1kg. I'll shift the tick over this way as there's actually an explanation about the answer. – joe92 Aug 20 '18 at 10:02
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Plato is just percentage by weight of extract in a solution, so you don't need a table. Any volume of wort at 12 plato is 12% extract by weight. So if you have 1 litre of it, 120g of it is extract. That's all you need.

I'm of the firm opinion that plato is the way to go, precisely because of this simplicity. The unit accounts for volume automatically, and being fully metric and decimal, is a breeze to use. No PPG, or sucrose contribution of 46ppg or any of that nonsense, just multiplying percentages.

10L @ 12P = 10 x 12% = 1.2kg extract conversely 9kg extract in 100L water = 9/(9+100) = .0825 = 8.25P

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  • While you don't need a table per se it sure speeds things up during recipe creation – joe92 Aug 21 '18 at 9:34
  • I don't reckon it does, if you're after extract per litre, as the OP is, you just shift the decimal place in your head. 12 Plato, 120g per litre. 50 Plato, 500g per litre etc. – Frazbro Aug 21 '18 at 9:36
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    I am the OP ;) Also, that's slightly wrong I've been reading. Going from my OP of 12 Plato, if you were to add 12g of sugar to 88ml of water you would get 100g of water, but not 100ml. For it to equal 100ml you would need 12.58g of sugar for 12P. That's the point of Specific Gravity, the difference in water levels at the same weight. 30 Plato does not equal 30g per 100ml, it is 70ml + 30g of sugar for a total weight of 100g. To make it 100ml at 30 Plato you would need 33.88g of sugar. – joe92 Aug 21 '18 at 9:50
  • Ah sorry, missed that on my phone. Yeah, that's why Plato is technically %by weight. The difference is usually smaller than noise though, so if you're after convenience, shifting the decimal place works perfectly. If you're after perfect precision, you're going to need pretty good instruments to know how close you're getting. You're right in the details, but in practice the difference is negligible. – Frazbro Aug 21 '18 at 9:55
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After much more scouring of the web googling the question in various and sometimes outlandish ways I stumbled across the following forum thread from 2006 which appears to answer my question:

https://discussions.probrewer.com/showthread.php?4636-Extract-Tables

Someone provided a table for the degrees plato and lbs. extract per BBl and kgs extract per hl.

I have expanded is slightly and present the table here should anyone in the future require this knowledge.

Degrees    | Potential | kg Extract    | lbs. Extract | lbs. Extract     | lbs. Extract
Plato (°P) | Gravity   | per hL (100L) | per US BBL   | per Canadian BBL | per UK BBL
-----------------------+---------------+-----------------------------------------------
8            1.032     | 8.27          | 21.36          20.69              29.79
9            1.036     | 9.34          | 24.12          23.36              33.64
10           1.040     | 10.42         | 26.90          26.05              37.52
11           1.044     | 11.50         | 29.70          28.77              41.42
12           1.048     | 12.59         | 32.52          31.50              45.36
13           1.053     | 13.69         | 35.36          34.25              49.32
14           1.057     | 14.80         | 38.22          37.02              53.31
15           1.061     | 15.92         | 41.10          39.81              57.32
16           1.065     | 17.04         | 44.00          42.62              61.37
17           1.070     | 18.17         | 46.92          45.44              65.44
18           1.074     | 19.31         | 49.86          48.29              69.54
19           1.079     | 20.46         | 52.82          51.16              73.67
20           1.083     | 21.61         | 55.80          54.05              77.82
21           1.087     | 22.77         | 58.80          56.95              82.01
22           1.092     | 23.94         | 61.82          59.88              86.22
23           1.096     | 25.12         | 64.86          62.82              90.46
24           1.101     | 26.30         | 67.92          65.78              94.73
25           1.106     | 27.50         | 71.00          68.77              99.02
26           1.110     | 28.70         | 74.10          71.77              103.35
27           1.115     | 29.91         | 77.22          74.79              107.70
28           1.120     | 31.12         | 80.36          77.83              112.08
29           1.124     | 32.35         | 83.52          80.89              116.49
30           1.129     | 33.58         | 86.70          83.97              120.92

The potential gravity is calculated using the following formula*:

SG = 1 + ( plato / (258.6 – ( (plato/258.2) * 227.1) ) )

*https://www.brewersfriend.com/plato-to-sg-conversion-chart/

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