How to adjust F.G.

[LuNchBoX1371]

So i brewed this beer on new years eve and it came out great; the only thing it that i missed my O.G. by 10 points. How do i adjust my F.G.? Is it just take 10 points off of the O.G. reading and there you have your F.G.? Thanks for the help

 

[Palazar]

I've only brewed one batch so don't consider me any sort of authority on the matter but if you've already pitched I don't think it will be possible. My advice would be to wait on your brew for a week afterwards, check your gravity over the course of several days. If it stays constant, you are golden and should bottle.

Sorry about the missed gravity btw I did something similar on my own (a porter) still tasted damn good though. Good luck!

 

[wilconrad]

You can adjust gravity down fairly easily by adding boiled/cooled water; adjusting the gravity up, however, is not feasible after the boil has been completed.

What's your situation? Do you need to adjust up or down? Has the beer completed fermentation yet?

 

[bajaedition]

the FG is effected by 2 things you should be worried about. (there are others but these are the 2 big ones)
un fermented types of sugars in thee wort
the attenuation of the yeast
the amount of those sugars is set by your use of specialty malts (simple explanation not complete)
the attenuation is your choice of yeast strain.

So those are already set and you are not going to effect them now

(disclaimers put in to simplify answer and not have to have a science class here)

 

[bbohanon]

OG is what it is when you finalize the wort and pitch the yeast. Its not adjustable at that point.

If you missed it by 10 points, its not the end of the world and I am sure the beer will turn out fine.
It may not hit the ABV you want, but again, that's still not the end of the world.

Missing OG can be due to alot of different factors depending on how and with what you brew. Was this an extract you did or brew an AG batch?

Bottom line, you took the OG and pitched, now let it ride for 3 weeks in the fermenter and take a FG reading for 2-3 days at the end of the 3 weeks to be sure its done before bottling or kegging.

Use any of the online calcs to figure your ABV and total efficiency once you get your FG reading and then start looking into how to make adjustments to your equipment, ingredients or process to get more efficiency out of your brews to start nailing your OG numbers going forward.

 

[wilconrad]

the FG is effected by 2 things you should be worried about. (there are others but these are the 2 big ones)
un fermented types of sugars in thee wort
the attenuation of the yeast
the amount of those sugars is set by your use of specialty malts (simple explanation not complete)
the attenuation is your choice of yeast strain.

So those are already set and you are not going to effect them now

(disclaimers put in to simplify answer and not have to have a science class here)

I'd add a 3rd "big thing": the O.G. of the wort. This can be adjusted down easily through dilution; adjusting up is not possible once you've completed the boil.

Also, in addition to the use of specialty malts, the amount of unfermentable sugars in your wort is heavily influenced by mash temp.

 

[ACbrewer]

OP- you 'missed by 10 points' High? or Low? what was the OG and was is the style.

...the O.G. of the wort. This can be adjusted down easily through dilution; adjusting up is not possible once you've completed the boil.
.

Actaully increasing the OG is fairly easily done. Add some dme. You don't even need to get it fully disolved, the diffusion and the yeast will do that for you. 1LB of DME will add about 8 or 9points in a 5 gallon batch. A little less if you make a slurry first with fresh water. Sugar can also be used, but I don't recomend it - because it thins the beer. Honey can be used, as can maple syrup ($$ and $$$$) but these also change the style of the beer. Better to use DME if you need to add more points of sugar.

I know that AG brewers generally look down of adding DME, but adding DME isn't a problem.

 

[ACbrewer]

So i brewed this beer on new years eve and it came out great; the only thing it that i missed my O.G. by 10 points. How do i adjust my F.G.? Is it just take 10 points off of the O.G. reading and there you have your F.G.? Thanks for the help

OK OP reread this...

What I'm reading is "My OG was suppsed to be 1.045 but came out 1.035"... "what should I expect my FG to be, it was going to be 1.011"

It will not be 1.001. Usually with beer you can take the OG (1.045) and just look at the end (45). Take 1/4 of that (11) and have the FG (1.011). In the case of 1.035, we get about 1.009 using this 1/4. This is because attenuation is about 75% (meaning about 75% changed by the yeast.). Some are as low as 70 and other as high as 80, and other things influence this, but the 75%/25% rules is a good guide.

This mean in your case if the OG was off by 10 points, adjust your expected FG by about 2.5.

 

[Palazar]

I'd add a 3rd "big thing": the O.G. of the wort. This can be adjusted down easily through dilution; adjusting up is not possible once you've completed the boil.

Also, in addition to the use of specialty malts, the amount of unfermentable sugars in your wort is heavily influenced by mash temp.

This. I was wondering though, if op does not care about hop bitterness, can't he just re-boil down to an acceptable gravity, re-hop, and pitch again? Just wondering here.

 

[wilconrad]

OActaully increasing the OG is fairly easily done. Add some dme. You don't even need to get it fully disolved, the diffusion and the yeast will do that for you. 1LB of DME will add about 8 or 9points in a 5 gallon batch.

I guess you could try this. Call me a purist, but if I missed my gravity on the low side I would definitely prefer to just let it ride rather than adjusting up with some DME.

 

[ACbrewer]

I guess you could try this. Call me a purist, but if I missed my gravity on the low side I would definitely prefer to just let it ride rather than adjusting up with some DME.

you're a purist....

But seriously, at this point if it was brewed 14 days ago, there is little point adding any more fermentables. (dme, lme, sugars etc.) that is what you do to make a specific style on brew day or as late as yeast pitch +1 day. After that, letting it go and drinking up.

If the question was about finding a new FG, then my 2nd post is what he is after.

 

[LuNchBoX1371]

OK OP reread this...

What I'm reading is "My OG was suppsed to be 1.045 but came out 1.035"... "what should I expect my FG to be, it was going to be 1.011"

It will not be 1.001. Usually with beer you can take the OG (1.045) and just look at the end (45). Take 1/4 of that (11) and have the FG (1.011). In the case of 1.035, we get about 1.009 using this 1/4. This is because attenuation is about 75% (meaning about 75% changed by the yeast.). Some are as low as 70 and other as high as 80, and other things influence this, but the 75%/25% rules is a good guide.

This mean in your case if the OG was off by 10 points, adjust your expected FG by about 2.5.

Thank you thats what i was looking for! Ok thank you for your help

 

[LuNchBoX1371]

You can adjust gravity down fairly easily by adding boiled/cooled water; adjusting the gravity up, however, is not feasible after the boil has been completed.

What's your situation? Do you need to adjust up or down? Has the beer completed fermentation yet?

I was short of my o.g. And the fermentation is complete i was just wondering how do i calculate for my new f.g. from my measured o.g.

 

[MindenMan]

I was short of my o.g. And the fermentation is complete i was just wondering how do i calculate for my new f.g. from my measured o.g.

I would take the easy road. I would use a free brewing software and plug in everything to match your predicted o.g., then cut back on the grain bill weights until you get down to your measured o.g. At that point, your new f.g. should be staring you in the face.

 

[bajaedition]

I'd add a 3rd "big thing": the O.G. of the wort. This can be adjusted down easily through dilution; adjusting up is not possible once you've completed the boil.

Also, in addition to the use of specialty malts, the amount of unfermentable sugars in your wort is heavily influenced by mash temp.

basically I was referring to what effects it in the fermenter, I do not think dilution of the wort is in spirit of the original post.

high use of specialty grins, carmalization of the wort, the list can go on, I agree. just trying to keep it simple with the spirit of the first post

 

[kh54s10]

I was short of my o.g. And the fermentation is complete i was just wondering how do i calculate for my new f.g. from my measured o.g.

You don't do anything to calculate FG. FG is just the reading of the gravity when the fermentation has finished.

What I have not seen asked is, was this and extract kit? If it was, you used all the ingredients and ended up with the right volume, your gravity would be what the kit called for. It is common for a gravity reading to be off due to top up water not fully mixing.

If it had no top up water and you are looking for the "predicted" FG you can go to a calculator, input all the ingredients then scale the recipe until it shows the OG you had and it should give you a new "predicted" FG.

Personally I would not worry about that since I find my FG is often quite different than the predicted. Just make sure it is stable before bottling.

 

[LandoLincoln]

I was short of my o.g. And the fermentation is complete i was just wondering how do i calculate for my new f.g. from my measured o.g.

It would be nice if you could say, "well, my OG is 1.060 and the yeast package says it has an attenuation rate of 77%, so therefore...my FG should be x." Unfortunately, there are other factors that have a big affect on attenuation, like the viability of the yeast and what happened in your mash tun, the pH of the water, what minerals are present in the water, how much oxygen the yeast had introduced post-boil, temperature of the fermentation, etc. etc.