Just add water

[whovous]

So, in addition to forgetting the yeast for last night's brew, I missed my target volume by a mile and wound up adding more than a half gallon of bottled water to get back to my 2.5 gallon target. The wort is sitting in my fermenter, waiting for me to pick up the yeast and to wave my magic oxygen wand before pitching tonight.

Is there any way I can get a reliable OG from this? Will just letting it sit for 24 hours (as I will do by default) be enough? Do I need to stir like crazy? Will oxygenating do the trick?

If I cannot get a reliable OG, does it matter if I do not stir and just oxygenate and pitch? Will the fermentation process take care of the rest?

 

[TheHappyHopper]

Is there any way I can get a reliable OG from this? Will just letting it sit for 24 hours (as I will do by default) be enough? Do I need to stir like crazy? Will oxygenating do the trick?

I would add the water and then stir or shake the fermenter for a minute or so to get it all mixed up - then take your OG reading. Then just oxygenate and pitch your yeast - you should be fine.

 

[JohnSand]

+1. You added water, mix it and check your gravity. If you are within a few points, ferment.

 

[whovous]

And if I am not within a few points? Still ferment, right?

 

[william_shakes_beer]

Its your beer, do what you want. But why not work the other way; measure your OG less the top off water, and calcualte how much water you need to add to get "down" to your target OG? IMHO too many of us brew to volume not gravity.

 

[andy6026]

It sounds to me like you've already added your top-off water, so the above suggestions aren't particularly helpful except should you be in the same boat again further down the road.

IF you made this beer from an extract kit and you now have the target volume, then don't worry - your OG will be pretty much bang-on target. It's impossible to mess that up. In this case I wouldn't even bother taking an OG reading (assuming you know that the kit says it will be). Instead just oxegenate the wort (if possible) and pitch the yeast.

If it's not from a kit, you can still go ahead and pitch the yeast without knowing the OG (you'll still get beer that's just as good without taking a reading, you'll just have to guess how much alcohol is in it). However, if you want you can give it a good stir and take a reading (preferably before you pitch the yeast).

You should note that leaving wort sitting with no yeast and then having to open it up later to oxygenate and pitch yeast makes you more susceptible to getting an infection. It's during the time that the yeast is sitting cool and before your intended yeast takes hold in it that wild yeast and other bacteria want to get in there and f*** up your beer. It's not the end of the world though - so long as your sanitation is good and you don't monkey around too much with the lid off you should be fine. Lots of brewers actually let it cool naturally before pitching and there's even open-top fermentation practices, although I admit it's not something I want to try myself.

 

[whovous]

Its your beer, do what you want. But why not work the other way; measure your OG less the top off water, and calcualte how much water you need to add to get "down" to your target OG? IMHO too many of us brew to volume not gravity.

With the benefit of hindsight, that is what I should have done. But as my other recent post "Sweet Bejezus I Forgot the Yeast!" suggests, I was in enough of a panic about the yeast that I was not working with much foresight at all. Gravity not volume seems an obvious goal, once I actually stop to think about it. It really does not matter just how many bottles I fill.

Can you talk me through the math for the next time this happens? Before adding the water, my OG was 1.070. I had 1.75 gallons of water. How much water should I have added to get to 1.065? A bit less than 7 oz?

And what did I actually wind up with? OG 1.070 w/ 1.75 gallons. Add 0.75 gallons at 1.000. Does that equal 1.049?

Do we have enough information to calculate my likely eventual ABV here? The original target ABV was 7.2% with an OG of 1.064 and an FG of 1.012. Or is this just not enough information?

 

[whovous]

Oh, this is from my own recipe, as fed to the Brew Shop Android app. It is all grain. You are correct, Andy6026, that the water is already added. I will buy the yeast this afternoon and pitch tonight.

 

[andy6026]

Im not sure if you'll need to stir it, but if intuition serves me correctly the water should mix with the wort fine over time and give you an even beer by the time fermentation is finished... so pitching the yeast is probably the only thing you need to do - an OG reading is optional if you want to calculate your final Abv and oxygenation does help the yeast to multiply, but unless its a really high gravity beer, you can most certainly get away without oxygenating if you're more concerned about introducing an infection.

 

[whovous]

OK, after letting it sit and mix on its own for almost 20 hours, I gave it a decent shake and measured it again. I got a reading of 1.049 as I predicted above, so at it seems I have figured out at least a little bit of the math. I played around with the efficiency numbers in my app until I got the same reading. This watering down corresponds to an efficiency of 52% (ugh) and suggests my FG should be 1.009 in a week or two. This corresponds to an ABV of 5.2%. The scary part is that my IBUs jump all the way to 86.8. I confess I am not sure I understand why decreasing efficiency/ABV increases IBUs, but so it goes.

I oxygenated and added yeast, then stuck the fermenter in a cool dark closet. 9-10 hours later, and it is bubbling like a mo-fo.

So, another question. I was too lazy to mix up a batch of Star-San, and I do not own any vodka. I did find a bottle of Ouzo in the cupboaard that I am never going to drink, so I put the blow-off tube into a few ounces of that. I can definitely smell it as the bubbles pop, currently at a rate of 2-3 bubbles per second. This smell is not likely to find its way into my beer, is it? I will get over it if it does, but I presume the gas travels in one direction only. Amiright?

 

[william_shakes_beer]

Can you talk me through the math for the next time this happens? Before adding the water, my OG was 1.070. I had 1.75 gallons of water. How much water should I have added to get to 1.065? A bit less than 7 oz?

1. You need to wrap your head around one simple thing: once you complete your mash and pull the bag, you can neither add nor subtract sugar, only water, by topping off (reduce SG) or boiling off ( increase sg). Once you understand that, the math is simple.

CG = current specific gravity
CV = current volume
DG = desired gravity
DV= desired volume

To keep me sane, I first calculate the amount of sugar in the pot. Your example doesn't tell me how many gallons at 1.070 you had, so let's assume 5 gallons. That means you have 1.070 X 5 gallons or 5.35 points of sugar. Set that aside and continue.

DV=(CG/DG)*CV

DV=(1.070/1.065)*5 = 5.0235 gallons. Therefore you need to add .023 gallons.

To cross check ( remember, you're not adding sugar, only water so the sugar amount should be the same) 5.023*1.065=5.349. OK.

Also works when you need to boil off excess water to increase SG.

 

[whovous]

Thank you, William Shakes Beer.

After the boil, I found myself with 1.75 gallons at 1.070. That gives me 1.8725 sugar points.

CG = 1.070
CV = 1.75
DG = 1.065

1.070/1.065 x 1.75 = 1.7582 gallons. I needed to add 0.0082 gallons to hit my target gravity, rather than the 0.75 gallons I added to hit my target gravity. That is just over an ounce. Yikes.

As I think about this, it seems intuitively obvious that hitting the target gravity is more important than hitting the target volume. So obvious, in fact, that it made me wonder why I was concerned with volume at all. But then it occurred to me that virtually all my experience has been with one gallon kits. If you make something that small and come up a quart low, there's hardly enough left to even bottle.