hist-brewing: Sweetening meads and hydrometer questions

[NeophyteSG at aol.com]

In a message dated 7/11/00 8:11:56 AM Pacific Daylight Time, 
WyteRayven at aol.com writes:

> If I start a mead, and take a hydrometer reading, and then at the first 
> racking I sweeten the mead, do I take a second reading before or after I 
> sweeten? If I then sweeten a third time, do I use the original hydrometer 
> reading for comparison, or the second reading? 
>  
>  Is there a book or a web page that explains hydrometer use more in depth? 
> The instructions that mine came with are woefully inadequate.
>  

A hydrometer measures the density of a fluid relative to the density of 
water.  For winemaking, that's a range of around 0.990 to around 1.180, with 
water at 60F measuring 1.000.  You'll want to calibrate your hydrometer by 
measuring 60F water and seeing if there's a discrepancy, as accuracy can vary 
with different hydrometers and manufacturers.  If there is a difference, 
you'll adjust all your subsequent readings up or down by that much.  

If you're measuring at a temp other than 60F, you'll have to adjust the 
reading according to the following scale:

 50F     -0.0005
 60F      0
 70F     +0.001
 77F     +0.002
 84F     +0.003
 95F     +0.005
105F    +0.007

For example, if it measures 1.080 at 95F, the actual SG would be 1.085 (1.080 
+ 0.005).  If your hydrometer also has a Brix scale, that tells you what the 
percentage of sugar by weight is in the must, with a range of around 0% to 
38%.  

The hydrometer's alcohol scale measures the must's *potential* alcohol if all 
the sugars were to be fermented out.  Whether you actually achieve that 
potential is largely a function of the yeast you choose.  You can determine 
the *actual* alcohol percentage by taking an initial reading prior to 
fermenting and subtracting the reading at the end.  For example:

Initial: 1.080SG    10.5%
Final: 1.010SG      1.5%

According to this example, your final product would have around 9% alcohol by 
volume.  If, for example, you were making a "Heroic" mead (around 5# 
honey/gallon) by adding the honey in stages, you'd also take SG readings at 
the beginning and end of each stage, summing the alcohol percents for the 
final.

Hope that helps clear up some of the mystery.

Warm Regards,
Shawn

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