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-   -   O.G./F.G. questions (http://www.homebrewtalk.com/f39/o-g-f-g-questions-365671/)

 shlitzcan 11-05-2012 03:40 PM

O.G./F.G. questions

Whats the calculation equation to figure your abv from specific gravities?:rockin:

 GilSwillBasementBrews 11-05-2012 03:44 PM

OG - FG x 131 = ABV

 Pappers_ 11-05-2012 03:52 PM

Hi Shlitzcan and welcome! I've moved your question from the Introductions forum to the Beginner's Brewing forum. Don't take that as any kind of admonition - its not, just keeping things in good order. You might want to spend some time looking through the forums, there are a lot of them!

Again, welcome! :mug:

 shlitzcan 11-05-2012 03:53 PM

wow thats cool. ok another question. i just transferred a robust porter last night and my gravity reading is 1.020. the last time i brewed this beer i could only get it down to 1.018 and i had bottle bombs. i did a 7 day primary and a two week secondary and bottled for two weeks. for the first couple days the beer was awesome....then lots of head.....then blowing up in my cellar. how do i get that gravity closer to 1.010?

 J187 11-05-2012 03:56 PM

Quote:
 Originally Posted by shlitzcan (Post 4560310) wow thats cool. ok another question. i just transferred a robust porter last night and my gravity reading is 1.020. the last time i brewed this beer i could only get it down to 1.018 and i had bottle bombs. i did a 7 day primary and a two week secondary and bottled for two weeks. for the first couple days the beer was awesome....then lots of head.....then blowing up in my cellar. how do i get that gravity closer to 1.010?
Give us some details. What was your recipe, and what was your fermentation like - how did you control temps? What yeast? Did you rehydrate or make starter? How much did you pitch? When you bottled, did you batch prime? What sugar did you use? How much did you use? What volume of beer did you have?

 Pappers_ 11-05-2012 04:04 PM

The final gravity number isn't really the issue with bottle bombs. For example, I have a Wee Heavy (Strong Scotch Ale) that has a FG of 1.022 but it is completely done fermenting (I aged it for six months, I know its done). There is zero risk of bottle bombs with this beer, despite its high FG - the style calls for a high FG, by the way.

Two issues with bottle bombs: 1) is the fermentation complete? and 2) sanitation.

If your fermentation is complete, if the yeast are done working, you can bottle without fear of bottle bombs, regardless of the FG. For your Robust Porter, wait a couple of days and take another gravity reading. Then wait a couple of more days (if you're concerned) and take another reading. If the reading has stayed the same, then you know fermentation is done and it is safe to bottle.

An exception though is if you have wild yeast in the bottle - they can restart fermentation in your bottle and create bottle bombs. So be careful with your sanitation.

About your Robust Porter, often they will be a little drier than yours is now, around 1.012 - 1.015ish final gravity. But, if you are brewing with extract, often the final gravity will be a little higher than the standard range. There is no harm in letting it sit in the carboy/bucket for a few weeks, to let the yeast complete their work. In fact, the yeast will clean up after themselves, which is a good thing, if you give them a chance. In the future, there is no need to transfer to a secondary for this beer and many brewers would tell you that leaving it on the yeast is advantageous.

 shlitzcan 11-05-2012 04:08 PM

ok grains

LB OZ °L PPG
33% 5 ~ Pale Malt (Maris Otter)
Mash 3° 37
33% 5 ~ American Two-row Pale
Mash 1° 37
10% 1 8 Victory Malt
Mash 25° 34
10% 1 8 Muntons Chocolate Malt
Mash 345° 28
7% 1 ~ Briess Special Roast
Mash 50° 34
3% ~ 8 Briess Caramel 120L
Mash 120° 34
3% ~ 8 Dingemans Cara 20
Mash 21° 37
0% ~ 1 Muntons Black Patent

fermentation was awesome. temps are in my cellar set at 69 deg.

i used white labs British ale (wlp005) I made a 500ml starter w light dme 2oz by weight.

 J187 11-05-2012 04:15 PM

Quote:
 Originally Posted by shlitzcan (Post 4560342) ok grains LB OZ °L PPG 33% 5 ~ Pale Malt (Maris Otter) Mash 3° 37 33% 5 ~ American Two-row Pale Mash 1° 37 10% 1 8 Victory Malt Mash 25° 34 10% 1 8 Muntons Chocolate Malt Mash 345° 28 7% 1 ~ Briess Special Roast Mash 50° 34 3% ~ 8 Briess Caramel 120L Mash 120° 34 3% ~ 8 Dingemans Cara 20 Mash 21° 37 0% ~ 1 Muntons Black Patent fermentation was awesome. temps are in my cellar set at 69 deg. i used white labs British ale (wlp005) I made a 500ml starter w light dme 2oz by weight.
Cool. How about the priming the process? Batch prime? Amount of sugar, type of sugar, etc.

 shlitzcan 11-05-2012 04:19 PM

3/4 cup corn sugar 2 cups of water. i just stir it until it all dissolves. i use this for a 5 gallon batch. which is all iv'e ever done.

 Pappers_ 11-05-2012 04:22 PM

This isn't about bottle bombs, but if you are consistently getting higher final gravities than you want, lower your mash temp (148F - 150F will typically give you a dry, light bodied beer).

About your bottle bombs, give it time and make sure the fermentation is complete, and make sure your bottles and caps are sanitized well.

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