Why is my OG and FG way off?

[dlnash16]

Hi,

I just finished my first brew and bottled and the gravity wasn't what I expected based on beersmith. Now I realize I probably screwed something up but just need to figure out what it was. My OG was 1.042 and beersmith said it should be 1.048 and my FG was supposed to be3 1.012 and I measured 1.018. My recipe was:

6 lbs. Pilsner Liquid Extract
1 lb Crystal Malt 10L
1 oz. Cascade (60 min)
2 limes zest (12 min)
2 orange zest (12 min)
Nottingham Dry yeast

It took about 60 hours for fermentation to start went strong for a few days and after about a week I measured at 1.018. I left it for another 4 days and measured again and it was 1.018. So I bottled after 12 days.

I also just brewed a Pumpkin Ale and beersmith says OG should be 1.055 and I had a reading of 1.050. I just need to figure out if this is normal or I am doing something completely wrong. Thanks.

 

[Pharmguy]

It seems pretty common for OG readings to be low for extract brews. It could be old extract that can result in lower efficiency but more than likely you just didnt stir the wort good enough when you added the top off water. (Im assuming you did not do a full boil).

As far as your high Fg, dont know. You see that will Pm's and all grain but shouldnt be an issue with extract. Maybe a resident expert will chime in on this one.

 

[chase]

With extract brewing, it is very rare to not hit the predicted OG. One common mistake new extract brewers make is not mixing in the top-off water very well. If you add top-off water after the boil, but don't mix it in really, REALLY well, the denser wort sinks to the bottom leaving thinner wort at the top. Many people then draw a sample for gravity, but aren't getting an even sample. That is probably why your OG was low.

The FG is a different story. Reduced attenuation is usually because if insufficient aeration before fermentation. If you don't really, REALLY shake the living hell out of the wort before it ferments, the yeast don't grow well and they can't ferment out the beer all the way. This is usually what causes a high FG. Additionally, the fact that it took ~60 hours for your fermentation to begin stinks of pour aeration. If you are aerating well, and pitching enough yeast, it should take off in ~24 hours or maybe up to ~48 hours.

There are of course other reasons for why your gravities may be off, but I would be willing to bet that these two things are what happened.

If you think that they aren't, let me know, and I'll give you some more options.

 

[dlnash16]

Those could be the exact reasons. I did stir it but probably not enough. It has been about 24 hours on my new batch and I don't see anything. Would it hurt to really stir it up now or is it already in the process so I shouldn't mess with it?

 

[jescholler]

It's already in the process, so you should just leave it alone. Just because you don't see any activity doesn't mean it isn't happening. It takes a while for the CO2 to build up and get pushed out through the blow-off tube or airlock. Sometimes even during active fermentation you won't see any activity.

Pitching rate and aeration are critical for proper FG. If you haven't already, check out the pitching rate calculator at Mr Malty Pitching Rate Calculator.

 

[chase]

Pitching rate and aeration are critical for proper FG. If you haven't already, check out the pitching rate calculator at Mr Malty Pitching Rate Calculator.

While I think that is an excellent suggestion, I think for beginner brewers that are using dry yeast, they shouldn't have any trouble with pitching rate. That also assumes he is making standard gravity beers.

dlnash, just leave it. Come back to it in a week and check the gravity. If it has dropped, leave it another week and check it again. Keep doing that until the gravity isn't changing. It will give the beer time to finish fermenting, and to mellow out. There are probably going to be some signs of yeast stress due to the lack of aeration. Letting it sit for a while will help with that.

 

[The Pol]

Dumb question, is your hydrometer off? I mean, have you tested it in distilled water?

Also, I have never brewed extract, but I have read enough threads where people referred to the fact that extract generally contains more unfermentable sugars, and people can wind up with higher than anticipated FGs... just an idea.

 

[dlnash16]

Thanks guys. I did test the hydrometer in water and it was 1.000. I will let it go for the next week and check it....then give it another week and move to secondary after that. I will make sure to real mix my wort with the topped off water going forward.

 

[david_42]

Some people don't mix the wort enough because they are concerned about oxidation. This is the one time in the brewing process where more oxygen is good.

 

[ChshreCat]

A good rough pour or splashy siphon into the fermenter from your kettle is usually good to aerate it. If you use top up water from gallon jugs, you can also empty them about 1/4 of the way, cap them and shake them up good. Just make sure you splash good anytime you pour. I do all of the above and usually have a good layer of foam on top of the wort when I'm done. That's usually a good sign.