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Old 09-14-2009, 06:13 PM   #1
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Default SG questions...

I'm getting ready to do my first all-grain this weekend so I need to be much better about recording my gravities. I've been really bad about getting gravites during my extract batches. I'd like to get all the info I can so that I can calculate my brewhouse efficiency.

Do we check our original gravity after we boil or after we pitch our yeast?

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Old 09-14-2009, 06:14 PM   #2
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after the boil, before the pitch

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Old 09-14-2009, 06:21 PM   #3
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It'll work the same if you do it after pitching your yeast, but since you shouldn't return your sample back to the fermenter you'd just be wasting a little yeast. Just saying that if you forget to take it before pitching, you can still go ahead and it'll be accurate.

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Old 09-14-2009, 06:47 PM   #4
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Take your pre-boil too, so you can calculate if you need to dilute to hit your target post boil gravity, or if you have to add a little DME, or boil further to hit your target.

Are you using any brewing software? I think most all brewing software have calculators that make these calculations really simple. As well most of these equations are available in basic brewing books like Palmer's "how to brew"

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Old 09-14-2009, 06:59 PM   #5
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It's a must to take your pre-boil SG and OG (preferrably before the pitch) to accurately calculate your Brewhouse Efficiency.

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Old 09-14-2009, 07:12 PM   #6
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Take your pre-boil too, so you can calculate if you need to dilute to hit your target post boil gravity, or if you have to add a little DME, or boil further to hit your target.

Are you using any brewing software? I think most all brewing software have calculators that make these calculations really simple. As well most of these equations are available in basic brewing books like Palmer's "how to brew"
Thanks everyone for the responses! So if your OG is off preboil how do you know how much water to add or DME to add to adjust the gravity?
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Old 09-14-2009, 08:01 PM   #7
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Quote:
Originally Posted by Beavdowg View Post
Thanks everyone for the responses! So if your OG is off preboil how do you know how much water to add or DME to add to adjust the gravity?
Well, if you're a math wiz, you can do some calculations, or you can pony up for a copy of BeerSmith - there are hydrometer temp tools, boil off percent tools, dilution tools..........
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Old 09-14-2009, 09:38 PM   #8
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Thanks everyone for the responses! So if your OG is off preboil how do you know how much water to add or DME to add to adjust the gravity?
Pre-boil SG and OG are different, you want to measure your gravity before the boil and after it goes into the fermenter to calculate your brewhouse efficiency.

If you have a graduated bucket, keep track of your firt runnings, and sparge runnings (this will be your total pre-boil volume and when to measure yor pre-boil SG), normally you'll boil off about a gallon or so in an hour long boil depending on your equipment. If after your 60 minute boil you have less than 5.25-5.5 gallons then you will probably want to add some top-off water to achieve the proper volume (a graduated bucket makes this relatively simple). After adding to get your desired volume make sure your dilution water is mixed well and take your OG then pitch your yeast. Normally, if you boil off more than expected and have to add some water back your gravity will be very close to where it should be. In essence boiling is concentrating the wort, so adding water back is diluting it.

Also

FWIW, my first AG pre-boil volume was 7.5 gallons, after the boil I ended up with about 4.75 gallons, so I added about .75 gallons back in to achieve a volume of 5.5, my estimated OG was 1.045, I ended up with OG 1.046. I will adjust my pre-boil volume to be 8-8.25 gallons.
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Old 09-14-2009, 10:14 PM   #9
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Quote:
Originally Posted by Schnitzengiggle View Post
Pre-boil SG and OG are different, you want to measure your gravity before the boil and after it goes into the fermenter to calculate your brewhouse efficiency.

If you have a graduated bucket, keep track of your firt runnings, and sparge runnings (this will be your total pre-boil volume and when to measure yor pre-boil SG), normally you'll boil off about a gallon or so in an hour long boil depending on your equipment. If after your 60 minute boil you have less than 5.25-5.5 gallons then you will probably want to add some top-off water to achieve the proper volume (a graduated bucket makes this relatively simple). After adding to get your desired volume make sure your dilution water is mixed well and take your OG then pitch your yeast. Normally, if you boil off more than expected and have to add some water back your gravity will be very close to where it should be. In essence boiling is concentrating the wort, so adding water back is diluting it.

Also

FWIW, my first AG pre-boil volume was 7.5 gallons, after the boil I ended up with about 4.75 gallons, so I added about .75 gallons back in to achieve a volume of 5.5, my estimated OG was 1.045, I ended up with OG 1.046. I will adjust my pre-boil volume to be 8-8.25 gallons.
Thanks, Schnizz. When you're adding water to your wort to bring the volume up are you worrying about the sanitization of the water you're adding? In other words, are you just adding water from your tap or are you adding water that you've boiled for 15 minutes to get rid on any bugs?

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Old 09-14-2009, 10:32 PM   #10
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If you are going to add water, it's best to add it to the boil, and its best to add it before your late hop additions. this is because when you add it, it will stop your boil, and take some time to get back up to a boil.

This will not be such a big deal for you bittering hop addition, because adding 10 min to the 60 min hop addition will not add too much bitterness to the batch. If on the other hand if you wait till the end of the boil to add the water and then extend your boil for ten more minutes then you have extended your late hop addition that can really change the flavors and bitterness of the beer.

I guess you could boil some water separately and cool it down then add it, but It is fairly simple to do the dilution calculations, and add the water when you start the boil.

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