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	FORUM ON BEER, HOMEBREWING, AND RELATED ISSUES
		Digest Janitor: pbabcock at hbd.org


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Contents:
  Estimating Original Gravity ("A.J deLange")
  Re: Forgot to record the starting SG (stencil)
  Forgot to record S.G. (Scott Birdwell)
  Attention Arkansas Brewers ("Ken Haycook")
  re: Forgot to record the starting SG ("jeff_ri")


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Date: Wed, 23 Apr 2008 08:58:50 -0400
From: "A.J deLange" <ajdel at cox.net>
Subject: Estimating Original Gravity

There are several ways to estimate the original gravity. The easiest 
would be to estimate the moisture content of the honey (or measure it if 
you still have some). It's been a while since I've worked with bees but 
I think the maximum allowable moisture content fom commercial honey is 
14% (?). Thus your 29 lbs of honey contains 0.86*29 = 24.94 lbs sugar in 
15 gallons of solution. Let's guess that you used 14 gallons of water. 
This weighs 8.3*14 = 116.2 lbs which, with 24.9 lbs of sugar gives you a 
total of 141.14 lbs. Thus the strength of the solution is 24.94/141.14 
=  17.67 Plato. Consultation of the tables shows that a 17.67 P solution 
has a specific gravity of 1.073 (or just multiplying the "points" by 4 
gives 1.071) which means that the weight of the solution is 8.3*1.073*V 
= 141.4 pounds where V is the volume in gallons. Thus V = 
141.4/8.3/1.073 = 15.87 gal which means that the 14 gal guess was too 
much. So repeat with 13 gal which leads to 24.94/(13*8.3 + 24.94) = 
18.77 P and a specific gravity of 1.078 for a mixed volume of 
132.84/8.3/1.078 = 14.85 gallons which is less than 15 gallons so a 
guess of 13 gallons starting water is too small. At this point you can 
do a linear interpolation (the underlying math is not linear but close 
enough over this small range). The rate of change of final volume with 
repect to initial volume is (15.87 - 14.85)/(14 - 13) = 1.02 gal/gal and 
as you finished with 15 gallons which is 0.15 gal more than 14.85 you 
probably started with 13 + 0.15/1.02 = 13.147 gal. Using this as above 
the weight of water plus sugar is 13.147*8.3 + 24.9 = 134.02 pounds for 
a strength of 24.9/134.02 = 18.58 P. A solution of this strength has SG 
= 1.0767 for a final volume of 134.02/8.3/1.0767 = 14.9967 gal which is 
certainly close enough to 15. Thus your initial gravity was about 18.58 
P or 1.077 SG.

A practical one might be found by taking .29 pounds (4.64 Oz) of the 
honey and making 0.15 gal (38.4 fl oz) of must and then measuring the 
specific gravity of that.

Yet another method is to measure the alcohol content and true extract of 
the finished mead and back calculate the original gravity from that. As 
few have access to direct measurement of alcohol (not that hard with an 
ebulliometer) I won't go into how that's done but if you do measure 
alcohol or can get it done post again and I'll discuss how back 
calculation is done.

A.J.


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Date: Wed, 23 Apr 2008 10:37:52 -0400
From: stencil <etcs.ret at verizon.net>
Subject: Re: Forgot to record the starting SG

On Wed, 23 Apr 2008 00:34:07 -0400, 
in Homebrew Digest #5323 (April 22, 2008)
Gary Smith wrote:

>------------------------------
> I used 29 pounds of honey in 
>15 gallons and introduced this to the yeast bed of the batch I just 
>transferred. 

The usual rule of thumb is 42 point-gallons per pound of
honey, which works out to 1081.

Or put four ounces weight of honey in a jar, add a pint of
water (OR add water to make a pint - your post is ambiguous
on this point) and record the SG of this model.  This
mini-must can be added to the exsisting ferment without
harm.

gds, stencil




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Date: Wed, 23 Apr 2008 10:00:04 -0500
From: Scott Birdwell <defalcos at sbcglobal.net>
Subject: Forgot to record S.G.

Gary Smith wrote:

"Though this has to do with Mead & not Beer perhaps someone here has
the solution I need.

I was in a hurry as I had to leave for New Hampshire and was
finishing a batch of Mead before I left. I used 29 pounds of honey in
15 gallons and introduced this to the yeast bed of the batch I just
transferred. The original yeast was Wyeast sweet mead and a Champagne
yeast.

I forgot to record the starting SG..."

I was guess-timate your SG with the following formula:
honey generally has about the same density as malt extract, so:
1 lb. honey/water to 1 gallon = 1.036

29 lbs. X 36 = 1044 point divided by 15 gallons comes up just shy of  
1.070 .  That would be my best guess for your OG.  Hope this helps!

Scott Birdwell
DeFalco's Home Wine & Beer Supplies
Houston TX
www.defalcos.com




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Date: Wed, 23 Apr 2008 15:05:58 -0500
From: "Ken Haycook" <k.haycook at sbcglobal.net>
Subject: Attention Arkansas Brewers 

Announcing the first Homebrew competition for the Arkansas State Fair. More
information can be found on the web site www.centralarkansasfermenters.com.
Let me know if I can answer any questions. 

 

Ken Haycook, PMP

Kendel Group

(501) 351-3942



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Date: Wed, 23 Apr 2008 18:24:06 -0400
From: "jeff_ri" <jeff_ri at cox.net>
Subject: re: Forgot to record the starting SG

Hi All,

  In HBD #5323 Gary Smith asked about calculating the SG for a batch of 
mead.

  This is easy to do with the info you gave in your post.  The SG points are 
equal to the lbs of honey times the "points per lb per gallon", all divided 
by the volume of the batch.  The "points per lb per gallon" is the number of 
SG points you would get by dissolving 1 lb of honey into a 1 gallon batch 
size.  For honey, this number is approximately 35 (numbers for malt extracts 
and other fermentables are available too).

  For your example, the SG would be ( 29 * 35 ) / 15 = 67.7 (so the SG would 
be about 1.068).

Jeff McNally
Tiverton, RI
(652.2 miles, 90.0 deg) A.R.
www.southshorebrewclub.org



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