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Home Brew Forums > Home Brewing Beer > Brew Science > Hydrometer, correct use
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Old 10-01-2010, 01:27 PM   #1
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Default Hydrometer, correct use

Sorry if this is in the wrong section.

Can someone explain how to use these properly.

I want to know how to relate the figures to alcohol content.

Thanks

Jungle

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Old 10-01-2010, 01:34 PM   #2
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Hi Jungle. You take a hydrometer reading when you first put the wort in your carboy or fermenter. Use the scale that reads like a thermometer. Then when your beer is all done becoming beer, take another hydrometer reading. The difference tells you how much sugar was eaten up by the yeast, producing alcohol. Some folks here figure that by hand, I put it into brewing software (I use Beersmith).

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Old 10-01-2010, 01:40 PM   #3
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The formula for determining that, that pappers wusses out and uses beersmith for is, og-fg x 131 = %ABV. (That's probably the extent of my math ability to figure out.)

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Old 10-01-2010, 01:45 PM   #4
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And this video is the best I've seen to explain how to use it, it's also by one of our own Bobby M.

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Old 10-01-2010, 01:50 PM   #5
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The correct way to use a hydrometer:

1. Get the sample at the reference temperature (probably 60 F, should be printed on the hydrometer somewhere) and degassed.

2. Read at the meniscus.

This will give you the relative density of the wort at the beginning and end of fermentation which doesn't really tell you much about the alcohol content (for that you need starting and finishing extract) but you can make some assumptions and get pretty close using the formulae referenced above.

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Old 10-01-2010, 02:14 PM   #6
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Thanks for the replies and posts guys. I'm doing n investigation at uni using different sugars, and the hydrometer is the only apparatus we have access to.

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Old 10-01-2010, 02:15 PM   #7
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Quote:
Originally Posted by Jungle View Post
Thanks for the replies and posts guys. I'm doing n investigation at uni using different sugars, and the hydrometer is the only apparatus we have access to.
It really is the only apparatus you need.
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Old 10-01-2010, 02:30 PM   #8
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Quote:
Originally Posted by remilard View Post
1. Get the sample at the reference temperature (probably 60 F, should be printed on the hydrometer somewhere) and degassed.
If the temp is not exactly 60F you can adjust the reading to compensate. Even within 10 degrees of 60 and the reading will be fairly close. here is a link for adjusting the readings for temp. http://hbd.org/cgi-bin/recipator/rec...ydrometer.html
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Old 10-01-2010, 03:11 PM   #9
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If the temp is not exactly 60F you can adjust the reading to compensate. Even within 10 degrees of 60 and the reading will be fairly close. here is a link for adjusting the readings for temp. http://hbd.org/cgi-bin/recipator/rec...ydrometer.html
It's correct use to measure at the reference temperature, it may be acceptable to read at other temperatures and apply an adjustment.

If the goal is determining alcohol content based on relative density readings, you are already layering estimates on estimates, why make it worse?
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Old 10-01-2010, 03:22 PM   #10
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Originally Posted by remilard View Post
It's correct use to measure at the reference temperature, it may be acceptable to read at other temperatures and apply an adjustment.

If the goal is determining alcohol content based on relative density readings, you are already layering estimates on estimates, why make it worse?
I guess I'm just not that anal about what the alcohol is. I brewed for many years without using a hydrometer. I still made great beer. I do use one now but I'm not so hung up on being super accurate with it. If my readings are off by .001 then I'm OK with that.
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