question on alcohol level

[rich]

alright so I'm on my third brew, and with this one I am trying to really get into the nuts and bolts of it, instead of just winging it.
In terms of alcohol level, original gravity and final gravity, I'm finding things a little confusing. From what I understand, the final gravity should correspond with the alcohol level. However, I've been observing recipies from 'Brewing Lager Beer' and comparing the OGs and FGs with what the alcohol volume for each recipe is supposed to be, but neither values correspond with the alcohol volume. Shite, I'm confused with this, but I know it's really basic stuff. I'm looking to make a pale ale with 5% ABV, and would like to calculated to OG and FG.
If someone could drop a line and explain exactly what I need to do, on layman's terms, it would be appreciated.

Thanks

Rich

[paul84043]

There's a simple calculation.
OG - FG x133 (roughly) some peoples calc varies by a few hundreths of a point.
Say you do a brew that has an O.G. of 1.050, and a F.G. of 1.010

1.050 - 1.010 = .04 X 133 = 5.32 (%).

Pretty straight forward.

Hope that helps.

[GunNut76]

Yeah what paul said...or you can TRY THIS (http://hbd.org/cgi-bin/recipator/recipator) and play around with your recipe untill you get the ABV you want.

[brewmonkey]

Or try it this way....

Original Gravity 1.050
Minus Terminal Gravity 1.008

Equals .042
Times 105

Equals Alcohol by weight 4.41%
times 1.25

Equals Alcohol by volume 5.51%

[rich]

Thanks guys. That makes sense. I think I was getting my wires crossed with too much information. Actually, I have one book that explains the alcohol by weight formula, but doesn't continue onto the ABV times 1.25 for the ABV, and that's where the search (and confusion) got started. Now it makes sense.
One last question. I just want to make sure I have this straight.
I want to produce a pale ale with 5% ABV. I understand that in order to hit the target gravity, I'll have to take a gravity reading that will be plugged into a formula to predict the final gravity (then I'll plug the two values into one of the formulas that you guys provided, and I'll be able to gauge where I am). However, I've been seeing the term 'specific gravity'. I am gathering that this is a gravity reading taken before the wort is finished boiling. Is that right? And if so, at what point should this reading be taken? Should it be taken before any hops are put in? On that note: do the addition of hops have any effect on the gravity reading? (My concern is extending a boil while making gravity adjustments... and overboiling the hops or something. Is that a risk?)
Alright guys. Thanks for putting up with these questions.

Rich

[b3s]

specific gravity (a comparison of a substance's density to that of water -- in the brewing universe the substance would be sugar) is what you are measuring when you take OG and FG readings. So OG would be the SG after boil, FG would be the SG after fermentation.

[toneyc]

We as hombrewers generally drop the word "specific". Technically, OG and FG should be OSG and FSG, Original Specific Gravity and Final Specific Gravity.

:)
Toney.

[Jughead]

And be aware that the hydrometer will read differently depending on the temp of the sample. I take the OG reading after cooling the wort to my yeast pitching temp. If you want to take readings while the wort is still hot from the boil, you would need to correct the reading for the given temp. You hydrometer should have come with a conversion chart.

I wouldn't try to make any gravity adjustments during the boil. After you have cooled the wort and are ready to pitch the yeast, take a reading. If you really want to adjust the gravity then, you could add water, or extract depending on which way you want to go.

I myself don't worry about a few points either way.

Cheers

[brewmonkey]

Originally posted by toneyc
We as hombrewers generally drop the word "specific". Technically, OG and FG should be OSG and FSG, Original Specific Gravity and Final Specific Gravity.

:)
Toney.

Original and terminal as well.

[rich]

Thanks for the collective advice. Much clearer now. Based on the feedback, I shouldn't take a gravity reading during the boil, and can make adjustments to the gravity after the boil. Adding water sounds easy enough, but in terms of adding additional malt, is it okay to add the malt after the boil? Does it not have to go through a boil itself? I thought that it did. I guess that's why I was asking when the best time is for adjustments to be made. Adding malt after the boil definitely sounds easier than after the boil.

[rich]

Correction to the last line:
"Adding malt after the boil sounds easier than adding additional malt DURING the boil."

Sorry about that.

[b3s]

i only just started correcting gravity. i do my correction during the last 15 minutes of boil. right before adding aroma/flavoring hops, i take a sample and put it in the freezer for a few minutes, add my hops, then take a temp test of the wort, quick hydrometer test, and correct for temperature and either add extract or water based on the calculations on pages 33-39 of designing great beers.

[paul84043]

I think that most of us don't stress too much over the details....I make a batch, and if I want to change it, I'll add or subtract something the next time I make it.
It's always good either way.