Final gravity problems.

[UoweMe]

Ok. First off I am fairly new at brewing so the guys at the home brew store give me a lot of help with my grain mixing. When I talk to them about the type of beer I want to make they always ask me what I would like the final gravity to be. I like around 6-7 % most of the time.
My problem is, after brewing the beer and finishing fermentation my beers usually end up being around 4%? With 12 pounds I grain in a five gallon batch this blows my mind. Any suggestions on where I may be loosing my sugars, or maybe iota even a problem with the yeasts. I am doing all grain FYI.

 

[worksnorth]

Can you tell us what your initial gravity and your final gravity hydrometer readings are?

 

[billl]

I think you are confusing some terms here. Your final gravity is just how much sugar is left after the brew. You could have the same FG but have drastically different ABV depending on how much sugar there was to start.

What is your last recipe and measured original gravity?

 

[duboman]

The ABV of a beer is a relationship of the starting and final gravity of a beer.

In other words how much sugar was available at the beginning before pithing yeast and then how much sugar the yeast consumed and converted to alcohol-also know as attenuation of the yeast.

Some yeast will attenuate better than others and it is dependent upon the strain of yeast and the ferment able sugar of the wort.

Just because you use 12 lbs of grain doesn't mean you will have a high or low ABV beer as here are many factors involved in the production of the alcohol.

You can have a starting gravity beer of 1.060 that actually finishes with less alcohol than a 1.040 beer depending in how it attenuated.

You also want to read the gravity scale on your hydrometer and not the % scale.

When creating recipes you are calculating the potential extract of the grain bill based upon your efficiency %, extract, mash temp, yeast strain, etc. these factors will determine your estimated OG and FG of a given recipe

If you have not read "How To Brew" by Palmer I would highly recommend it!

 

[UoweMe]

My original gravity was about 1.050, after fermentation it was about 1.020? I hope this helps.

 

[freisste]

Assuming you are reading your hydrometer correctly (no offense, this IS a beginners forum), you are correct that you got 4%.

This may be a pretty complicated issue. Can you tell us about your mash procedure? Temp, time, each step...

This information will help to determine if you are getting sugar and if it is fermentable or not.

 

[duboman]

My original gravity was about 1.050, after fermentation it was about 1.020? I hope this helps.

Assume this was an extract recipe with or without steeped grains?

If so the OG was what the recipe stated and assumes you hit your volume with top off water.

Regardless of what you read the OG will be what the recipe stated.

FG at 1.020 is a common occupancy with extract brewing due to the unpredictable nature of extract, poor aeration and under pitching yeast and fermentation temperature control-all things that improve with experience.

Gravity readings need to be temperature corrected and the hydrometer should be calibrated. It should read 1.000 in distilled water at the calibration temperature stated on the hydrometer paper.

Again, I recommend the book mentioned above and you can also google it as there is a free online version, a little dated but valuable none the less

 

[freisste]

Assume this was an extract recipe with or without steeped grains?

Again, I recommend the book mentioned above and you can also google it as there is a free online version, a little dated but valuable none the less

OP says it is AG. I recommend you read his post .

 

[woozy]

My original gravity was about 1.050, after fermentation it was about 1.020? I hope this helps.

Some formulas:

Alcohol by Volume = (OG - FG)*131 = 3.93% ~ 4%
Atenuation = sugars converted/original sugars = (OG - FG)/OG in points = 30/50 = 60%. About average. Teensy bit low.

My newbie advice. (And I warn you in advance I might not know my ass from my elbow.) Is that if you want 6% beer made with 60% attenuation then you want the original gravity the *potential* for 100/60 * 6% = 10%. 10% *potential* is 10/131 = .076 so you want an O.G of 1.076. (O.G. of 1.076 with attenuation of 60% means final gravity of 1.030. og -fg * 131 = 6%)

Increase your grain bill by 76/50 or 12*76/50 = 18 lbs.

Hmmm. *That* doesn't seem right, does it.... There's probably someway to get higher attenuation than 60%. And you can probably increase your mashing efficiency.


Grain is has roughly 35-38 units of extractable sugars (lets say 37). These "units" are points per pound per gallon or in other words there is enough sugar in a pound of grain to raise 1 gallon of water 37 gravity points. Thus 12 lbs has the *potential* to extract 12*37 = 444 of these units. This is enough to raise five gallons 444/5 = 88.8 pts or an original gravity of 1.0888 but you will *not* get this. No human being ever will.

Instead you got 5 gallons and 50 points or 250 of these 444 units so your efficiency was 250/444 = 56% which isn't great but isn't terrible either. But really isn't great. Usually one shoots for 75%.

75% would give you .75*444 = 333 of these units 333 units/5 gallons = 66.6 gravity points or an OG of 1.067. 60% attenuation would mean .6*67 = 40 gravity points converted for a final gravity of 1.027 and a final ABV of 40* 131 = 5.25%

You need bigger beers and higher attenuating yeasts for higher alcohol.

But then I'm still a newbie.

 

[freisste]

Here goes

Who crushes your grain? A finer crush can sometimes help get more sugar out.

What temperature do you mash at and what is your process? Lower temperatures make for more fermentable wort. Lower meaning 145-148. Lower than 145 and you are going to risk not fully converting. (Have you ever heard of the iodine test? You could try it to ensure conversion is complete.) And calibrate your thermometer just to be sure.

How do you sparge? I BIAB, so I squeeze the bag and then rinse and repeat. I get like 80%. I doubt you do the same with 12lbs, so I'm guessing you have a converted igloo cooler or similar. Walk us through your process.

What yeast are you using? Yeast crap out after a certain percentage of the job or a certain ABV, whichever comes first. For example, if a yeast is good for 80% attenuation or 8% ABV, you could mash 100lbs of grain into 5 gallons and only get 8% with a bunch of leftover sugar (I don't think this is your issue because you have low ABV and attenuation. Maybe temp control during fermentation?)

Getting the most out of your yeast depends on keeping them happy. Put in the right amount at the right temp, then hold the right temp. Fluctuations don't help the yeast do their job.

Again, this is a short list of things I see happen sometimes. This is certainly not exhaustive. If you can think of anything that will help us nail down your issue, let us know and we will try to provide some advice and guidance.

 

[JohnSand]

And if all of that seems like a lot of complicated technical chemistry, well, it is. But anyone can do it, you can too. Keep learning and practicing. I started with HME-Hopped Malt Extract- just add water, yeast, and time. It's the simplest way to make beer, allowing you to focus on process. If all grain is frustrating you, back up and start over simpler. Or forge ahead until you get it right. Either way, you'll make beer, which is pretty cool.