My fermentations never finish, please help!

My last 3 batches of beer have all suffered from stuck fermentation, and I think I've narrowed the problem down to my starters. I've been using Jamil's yeast pitching calculator, and these are all grain recipes. Mash temps have ranged from 149-158 and my beers always seem to get stuck around 1.026-1.030.

How much DME is recommended for use in a starter? I've been using enough to have a starting gravity of 1.035ish. Is this too high? And how long in advance should I make my starters? I've been doing them about 20 hours in advance, then pitching the entire thing into my primary fermenter.

Are you using a hyrdometer to measure gravity or a refractometer?

1.035 is a very good gravity for starter wort. The rule of thumb is 1g of DME for 10ml of water. This should produce a wort in the 1.040 range and that is good for starters.

20 hours is plenty of time.

What is the starting gravity of these batches. How long are you allowing for the fermentation. Do you oxygenate the wort? What's in the recipe? Is it all malted barley?

Your gravity is fine, just make sure it is tested. I suspect you are not letting your starters ferment long enough. 20 hours is fine, in OPTIMAL conditions and with very fresh yeast. Personally, I let my starters ferment out at least 3 days - typically an entire week. This way, I am absolutely certain it is completed. I also cold crash them after a few days and decant most of the liquid just before pitching. I reccomend trying a longer starter ferment, as there may be something in your process or ingredients that is not allowing 20 hours to be optimal.

Cheers mate

It sounds like your starters are fine. I'll bet that the problem lies either in your fermentation or its based on the beer (i.e., high high OG, a lot of unfermentables, extract, etc)

is your thermometer you use for mashing calibrated?

- I use a refractometer for measuring gravity.
- I use a digital thermometer but it hasn't been calibrated.

These beers have OG's ranging from 1.059 to 1.077, starters ranging from 1-4 litres. I generally see a vigorous fermentation for 2-3 days, then things slow down and freeze at 1.030ish for 10-20 days. Then I get pissed and dump them. Maybe aeration is my problem? How long would you generally aerate beers of this size?

I also use a pH meter during the mash and everything goes swimmingly. I hit all my targets etc.

Soma said:

- I use a refractometer for measuring gravity.

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Are you doing the calculation to correct the FG reading from the refractometer?

The presence of alcohol throws off refraction on FG readings, but you can calculate a real FG if you know the initial brix and the final brix.

http://www.onebeer.net/refractometer.shtml

If you are not correcting the reading, that explains the problem.

What kind of yeast are you using and what are your fermentation temperatures?

Oh sweet creator... this is the answer. Thank you!

Walker said:

Are you doing the calculation to correct the FG reading from the refractometer?

The presence of alcohol throws off refraction on FG readings, but you can calculate a real FG if you know the initial brix and the final brix.

http://www.onebeer.net/refractometer.shtml

If you are not correcting the reading, that explains the problem.

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Soma said:

Oh sweet creator... this is the answer. Thank you!

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Cool. I figured it was. Without a correction an average FG will look like it's in the 1.030's.

Soma said:

I generally see a vigorous fermentation for 2-3 days, then things slow down and freeze at 1.030ish for 10-20 days. Then I get pissed and dump them.

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I have to ask.... how much perfectly good beer did you unnecessarily dumped out thinking you had a problem?

wow I would have drank it anyways. I'm assuming it tasted fine. Who cares what the numbers read

maida7 said:

wow I would have drank it anyways. I'm assuming it tasted fine. Who cares what the numbers read

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+1 there.

I don't even check FG. I check OG to see how my mash efficiency was, but that's it.

Walker said:

+1 there.

I don't even check FG. I check OG to see how my mash efficiency was, but that's it.

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When I was extract brewing I went for years without taking any readings. Extract is VERY reliable for producing the starting gravity. If you pitch a good amount of healthy yeast and just watch the ferment you 98% sure when it's done. I never had a problem with a stuck or sweet beer.

Now that I brew AG I take more readings but it's just for record keeping and keeping track of things. I still judge the ferment finished by watching the yeast.

Walker said:

I have to ask.... how much perfectly good beer did you unnecessarily dumped out thinking you had a problem?

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I dumped 5 gallons of a Aventinus-esque 1.085 weizenbock :'(

And I came very close to dumping my ESB last night. Thank goodness for this board! Much appreciated again!

Did you ever taste anything before you dumped it? You've got an itchy trigger finger there