From the HBD Archive
From: Fred Eckhardt <eckhardt@pcez.com>
Subject: Alcohol conversion factors are not simple.
Date: 2000-11-04 22:58:46 GMT

Calculating alcohol contents has many variations, here is one set.
(c) Fred Eckhardt, 1995, 2000 all rights reserved.
TABLE I
CONVERSION FACTORS
SPECIFIC GRAVITY to DEGREES PLATO
by Fred Eckhardt, (c) 1995, 2000, all rights reserved

Specific Gravity factor degrees Plato
1.000 - 1.022 3.9 0 - 5.6
1.023 - 1.025 3.95 5.7 - 6.3
1.026 - 1.052 4.0 6.4 - 12.9
1.053 - 1.055 4.05 13 - 13.6
1.056 - 1.098 4.1 13.7 - 24
1.099 - 1.022 4.2 24.1 - 29
1.023 - 1.1127.5 4.25 29.1 - 30
above 1.127.6 4.3 30 and up

To convert specific gravity to degrees plato: first subtract 1.000, then
divide the remainder by the factor, i.e. 1.023, less 1.000 = 23 / 3.95 =
5.8Plato; or another example 1.096 less 1.000 = 96 / 4.1 = 23.4Plato.

To convert degrees Plato to specific gravity: Multiply Plato x factor, and
add 1.000. e.g. 12.1P x 4.0 = 48.4 = 1.048; another example 15.5P x 4.1 =
63.55 = 1.063.55 or 1064.
The Belgian degrees are equal to specific gravity, less 1.000, then divide
by 10. e.g. s.g. 1.062, less 1.000 = 62 / 10 = 6.2Bg.
To convert Belgian to Plato, first convert to s.g., then convert to
Plato. To convert s.g. to British, drop the decimal point. e.g. 1.056 =
1056Br.
All Calculations are according to standard published tables.

TABLE II
TABLE OF ALCOHOL FACTORS BY ORIGINAL EXTRACT IN DEGREES PLATO

Plato alcohol factor Plato alcohol factor
6 0.4073 16 0.4267
7 0.4091 17 0.4288
8 0.4110 18 0.4309
9 0.4129 19 0.4330
10 0.4148 20 0.4351
10.5 0.4158 21 0.4373
11 0.4168 22 0.4395
11.5 0.4177 23 0.4417
12 0.4187 24 0.4439
12.5 0.4197 25 0.4462
13 0.4206 26 0.4485
13.5 0.4216 27 0.4508
14 0.4226 28 0.4532
14.5 0.4236 29 0.4556
15 0.4246 30 0.4580
15.5 0.4257 ca31 ca0.4605
Compiled from Balling's tables, with the generous help of Fred Scheer,
BOSCO'S Brewing, Nashville, TN.
Not intended for professional use.

HOW TO USE THE CONVERSION AND ALCOHOL FACTOR TABLES TO CALCULATE
ORIGINAL EXTRACT, ABW, ABV, BEER OR APPARENT EXTRACT
(and other useless information)
by Fred Eckhardt, (c) 1995, 2000, all rights reserved.

To find alcohol content by weight (ABW), or Original Gravity/Extract, or
Beer Gravity/Apparent Extract, using these tables, you must first convert
the specific gravities to Plato (Table I). You need to know two of the
above figures to calculate the third.

To find ABW, subtract Apparent Extract (Beer Gravity) from Original
Extract, and multiply by the alcohol factor for that Original Extract (see
table).

To find apparent extract when you know Original Extract and ABW, divide the
ABW by the alcohol factor for that Original extract, subtract from Original
Extract.

To find beer gravity, de-carbonate the beer, and measure its specific
gravity, convert that to Plato, which will give you Apparent Extract (beer
gravity).

To convert ABW to ABV (alcohol content by volume), multiply ABW by 1.256,
and multiply that figure by the specific gravity of the beer (apparent
extract converted to s.g.). i.e. 5% alcohol in a beer with an apparent
extract of 2.8P/s.g.1.011: 5 x 1.256 x 1.011 = 6.35%ABV.

To find Original Extract when you know the Apparent Extract (beer gravity)
and ABW, start by guessing the original gravity, for example you can
convert ABW to ABV, then multiply the ABV by 10 for a ballpark OG, (less
1.000) which must then be converted to Plato. Now calculate the actual
Original Extract by dividing the ABW by the alcohol factor for the
approximate OE, and add that figure to the Apparent Extract. Suppose you
know the beer gravity to be 1.011, which is 2.8P, and the ABW to be 5%.
Convert that to ABV (above) 6.35%, then guestimate the OE, by multiplying
that (ABV) by 10, i.e. 63, 1.063, which is 15.5P, find the alcohol factor
for that (0.4257), divide the ABW by that, this gives a ballpark extract
drop of 11.75, which is added to the AE, 11.75 + 2.8 = 14.5P. You have to
do it all again to get the actual OE. So go through the sequence again,
using the correct alcohol factor for 14.5 (0.4236): 5 / 0.4236 = 11.8 + 2.8
= actual OE 14.6P x 4.1 = 59.9 = 1.060.

Please note that there are ways to do these calculations without
translating gravity to degrees Plato, but I haven't the time to do those
tables, and that's that. I have not found any tables in print, with proper
alcohol factors, for specific gravity relationships.





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