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Old 07-18-2011, 09:57 PM   #1
cadarnell
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I have been doing all grain brewing for about 15 batches of beer now .. I do them in my kitchen, on my stove. I can only boil about 4 1/2 gallons of wort comfortably, so to make a full batch I have to top off .. I have been getting some conflicting hydro readings pre boil and after topping off .. I havent been doing a post boil, before topping off reading, beacuse that wort is so much harder to cool than pre boil ... I always think my after topping off reading should be 2 to 4 points higher based on my pre boil reading .. so which one is more accurate? ... I'm thinking the pre boil is but, I swear I mix that water in really, really well .. thoughts ?? ..

 
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Old 07-18-2011, 10:03 PM   #2
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Are you accounting for temperature? The hydrometer should have a temperature value on it and you need to adjust for temperature. Most hydrometers are calibrated to yield the correct reading when the solution it is floating in is 60 degrees F.

This is an important thing people tend to overlook and could easily account for the variability you mention.

 
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Old 07-18-2011, 10:07 PM   #3
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A hydrometer with a temp valve on it? never heard of that one. But it should read 1.000 in water @ 60F. Mine does,so I'm good. Check yours & see what it says.
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Old 07-18-2011, 10:12 PM   #4
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Quote:
Originally Posted by Irrenarzt View Post
Are you accounting for temperature? The hydrometer should have a temperature value on it and you need to adjust for temperature. Most hydrometers are calibrated to yield the correct reading when the solution it is floating in is 60 degrees F.

This is an important thing people tend to overlook and could easily account for the variability you mention.
yea .. I cool the samples to 80 or a little lower and then take the reading .. then I type the numbers into brewing software to get my adjusted number.

 
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Old 07-18-2011, 10:15 PM   #5
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However well you think you are mixing the water in, it isn't well enough.
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Old 07-18-2011, 10:21 PM   #6
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Great help for hydrometer temp adjustments

http://www.brewersfriend.com/hydrometer-temp/

 
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Old 07-18-2011, 10:22 PM   #7
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Your pre-boil reading will be lower than your post-boil reading typically. But since you're adding water you are diluting back down. How much you dilute it depends on how much water you add.

So by "conflicting" do you mean your pre-boil is greater than or equal to your post boil reading?

As an example, say you get a pre-boil gravity of 1.042. Then you'll boil for 60 minutes or so and cool. Then you may be at 1.050. Then you're topping off with water (1.000) so you may be down to 1.044 or something like that. Really just making up numbers, but you get the idea of the up-down swing.

The gravity reading you care most about is what is going into your fermenter. i.e. your cooled post-boil reading.

 
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Old 07-18-2011, 10:25 PM   #8
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Quote:
Originally Posted by unionrdr View Post
A hydrometer with a temp valve on it? never heard of that one. But it should read 1.000 in water @ 60F. Mine does,so I'm good. Check yours & see what it says.
Not valve, value

 
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Old 07-18-2011, 10:31 PM   #9
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Quote:
Originally Posted by AnthonyC View Post
Your pre-boil reading will be lower than your post-boil reading typically. But since you're adding water you are diluting back down. How much you dilute it depends on how much water you add.

So by "conflicting" do you mean your pre-boil is greater than or equal to your post boil reading?

As an example, say you get a pre-boil gravity of 1.042. Then you'll boil for 60 minutes or so and cool. Then you may be at 1.050. Then you're topping off with water (1.000) so you may be down to 1.044 or something like that. Really just making up numbers, but you get the idea of the up-down swing.

The gravity reading you care most about is what is going into your fermenter. i.e. your cooled post-boil reading.
yea .. I learned the math to figure out how many points I lose to topping off ... but the way I do it it's really pretty simple to figure ... if my pre boil is 4.5 gallons at 1.052 and I top it back up to 4.5 gallons post boil, I should be back at 1.052 by my math .. maybe I am just not mixing the water well enough .. or I am using bad math

 
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Old 07-18-2011, 10:36 PM   #10
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Quote:
Originally Posted by Irrenarzt View Post
Not valve, value
Dang! my good glasses broke into several pieces a week ago,& I'm wearing my previous pair that are polarized. That,& middle age might be making me dyslectic.lolz. I just figure the temp adjustment if/when I really need to be picky. I'm not an AG'r,just steep now & then. But I could swear...new glasses needed...
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