Calculating OG after topping off

[edin88]

I brewed a saison and due to miscalculation with sparging and boiling, I ended up with a little more than 4 gallons of wort instead of the anticipated 5 gallons. The weird thing was when I took a gravity reading with the last bit of wort left in my kettle that I didn't transfer to the carboy, it was something like 1.08, Meaning I got more than 90% efficiency. I assume this is just because I boiled off way more than I should have, because I was shooting for an OG of 1.055 or around there (10.66 lbs Pilsner malt, 8 oz. caravienne, 2 oz. caramunich, 1 lb. candy sugar)

I made the decision to just buy a gallon of Poland Spring and pour it into my carboy. I didn't boil it beforehand cause I just am not that worried about an infection with bottled water.

The question is, how the hell do I estimate the OG with the extra gallon of water? oh and my hydrometer broke...(many things that could have gone wrong did on this brew day)

Thanks in advance

 

[twistr25]

You would mix in the water and then take a gravity reading. But first things first, you MUST have a hydrometer. You'll need it for FG anyway.

 

[edin88]

it's too late for measurements, i already have a very strong fermentation going, even if i got a hydrometer tomorrow - which im not going to do cause it's too far a drive to the lhbs - i still wouldn't get an OG but a SG

i need an estimate! I can't be the first person to do this and I know there's a loooot of smart people on here who might know some formulas to get me a ballpark estimate. 4 gallons of 1.08 wort + 1 gallon of water + Pi(r)^2 = OG right?

 

[buzbey]

If your og was 1.080 at four gallons it should be about 1.064 after adding another gallon

 

[acidrain]

You could calculate it if you know exactly:
Specific gravity and exact volume of the wort.
Exact volume of spring water added.

BTW, I haven't used a hydrometer in a long time.

 

[chickypad]

If your og was 1.080 at four gallons it should be about 1.064 after adding another gallon

Exactly. V1 x G1 = V2 x G2 where V = volume and G = gravity in pts.

80 x 4 / 5 = 64

 

[ACbrewer]

well if you have 1.080, and 4 gallons - that would make 320 points of sugar. (80*4) 320/5=64, so 1.064. When you take a hydro reading at the start it should have been about 1.064.

By now you have pitched the yeast

oh back to part of your question. you can figure the sugar points by multiplying the volume by the gravity (4 gallons by 80 points) gets a total sugar in the solution 320. So then divide it by the new volume - 5 gallons = 64.
And get a new hydrometer.

 

[buzbey]

You take the gravity 1.080 would be 80. times it buy amount of gallons to get the specific gravity points so 80X4=320. Then divide buy the amount of new gallons so 320 divided buy 5 = 64 so 1.064.

 

[edin88]

If your og was 1.080 at four gallons it should be about 1.064 after adding another gallon

That sounds pretty legit, how'd you come up with it though? I'm FAIRLY positive of the volume of post-boil wort, it had to have been been very close to 4 gallons cause with exactly 1 gallon of water added it's about 5 gallons total


I really need to draw out measurements on my carboy and kettle....

 

[Shaneoco1981]

1.064 should be pretty accurate. I punched it all into Beersmith, found you had about 70% efficiency, and then changed the volume from 4 to 5 gallons. It will be within 2 or 3 points... Lastly, you really can't take a measurement after you top off because water never mixes that great. Yeast do, however, a great job of mixing.

 

[edin88]

This site is so helpful it's insane.

Thank you VERY MUCH everyone!!

I studied political science, I'm very bad at math. I once bought a $150 couch with 2 of my friends, splitting the cost 3 ways. We're carrying the couch out and I go, "so what is this gonna be, like $47 each or something like that?" Yup. I divided 150 by 3 in my head and got 47 and change

 

[buzbey]

You can also use this calculation to figure out what your pre boil gravity will be post boil as well. Say you start at 7 gallons and boil it down to 5.

 

[Worticia]

((1.080*4 gallons) + (1.000 * 1 gallon)) / 5 gallons = 1.064