Complete Fermentation?

[ScienceGuy]

My wife and I just bottled our Red Ale and it tastes pretty good, but here's the rub. After two weeks in the primary, the bubbling was down to maybe one or two a minute, so I took a gravity reading. It showed that it wasn't done fermenting, but it just didn't seem like it was really moving on. I decided to just go ahead and bottle and let it sit in the bottles for carbonation (I'm up against a deadline.) So after all of that:
1. After fermentation settles like that, and I know it isn't done what can I do? Pitch a new yeast or add sugar?
2. Will letting it bottle age at room temperature (65-72 F) do anything for lessening the sweetness.
Thanks for the help!

[DannyW]

You might want to store those bottles wrapped in a plastic trash bag in a rubbermaid bin. In 2 more weeks they might be flat, they might be OK, or they might explode!

Now for wild-assed guessing on what will happen...

How low was "not done?" What was your OG and FG? Was this all grain or extract? If the former, mash temp? If the latter, what brand of extract?

How much yeast did you use, what brand, and at what ferm temp?

[Lufah]

In addition to Danny's questions, how much sugar did you use to prime with?

Travis

[ScienceGuy]

I used the old standby 3/4 cup sugar for priming. I might have been a little shy, but it was pretty close.
There wasn't any problem with carbonation, everything carbonated nicely; no pop tops or seepage (or explosions.)
I'll look in my book for the actualy O.G. and F.G. but I know it was 4.06%.
I was using DME from my LHBS for the most part, a few specialty grains that I steeped while waiting for the water to heat up. I don't recall the brand of the DME.
I used a single smack-pack of Wyeast 1332, with no starter. I fermented at room temperature, which ran about 71 F. There were some temperature swings of 4 degrees in there, which I know will impact the yeast's ability to reproduce effectively.
Thanks again.

[Lufah]

What you want to look at is the attenuation of the yeast. If you hit the target numbers for that yeast then you are good. If not you may need to look at your process. Things like aireation and yeast nutrient.

Travis

[ScienceGuy]

OK. School time.
How do I figure attentuation rate?

[Lufah]

I'm to lazy to type this all out...

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ATTENUATION

Attenuation refers to the percentage of sugar converted to alcohol. Apparent attenuation of yeast normally ranges from 67-77%. The attenuation is determined by the composition of the wort or juice and the yeast strain used. Each yeast strain ferments different sugars to varying degrees, resulting in higher or lower final gravities. That will affect the residual sweetness and body.

Really, it's slightly more complex than that (isn't everything ? :-).There's "apparent attenuation" and "real attenuation". The difference comes about because alcohol has a specific gravity less than 1 (about 0.8). Real attenuation is the percent of sugars converted to alcohol. So, if you had a 10% (by weight) sugar solution (about 1.040), and got 100% real attenuation, the resulting specific gravity would be about 0.991 (corresponding to about 4% alcohol by weight). The apparent attenuation of this brew would be 122%! George Fix published a set of equations relating apparent and real attenuation and alcohol content last year. For example, let

    * A = alcohol content of finished beer in % by wt

      and
    * RE = real extract of finished beer in deg. Plato.

Since A and RE are generally not known to us, additional approximations are needed. The following are due to Balling, and have proven to be reasonable. Let OE and be defined as follows:

    * OE = original extract (measured deg. Plato of wort)
    * AE = apparent extract (measured deg. Plato of finished beer).

Then,

    * RE = 0.1808*OE + 0.8192*AE,

      and
    * A = (OE-RE)/(2.0664-0.010664*OE).

The "tricky part" here is the expression of the sugar content in degrees Plato. This is a fancy term for % sugar by weight, and corresponds roughly to "degrees gravity" divided by 4. That is, a 1.040 wort has an extract of 10 degrees Plato. He goes on to calculate an example: To take a specific case, first note that from Plato tables an OG of 1.044 is equivalent to OE = 11.24 deg. Plato, while a FG of 1.010 is equivalent to AE = 2.4 deg. Plato. Therefore,

    * RE = 0.1808*11.24 + 0.8192*2.4 = 4.08 deg. Plato,

      and
    * A = (11.24 - 4.08)/(2.0664 - .010664*11.24) = 3.68 % wt.

The apparent attenuation is 74% (from 1.040 to 1.010), the real attenuation is (11.24 - 4.08)/11.24 = 64%. N.B. Most attenuation figures are given in terms of apparent attenuation.

(Thanks to Chris Pencis quoting Stuart Thomas quoting George Fix).

From... http://hbd.org/brewery/library/yeast-fa ... ttenuation

If you search around a bit you can find out more about it.

Your yeast should have attenuated 67-71%.

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1332 Northwest Ale Yeast. One of the classic ale strains from the Northwest U.S. Breweries. Produces a malty and mildly fruity ale with good depth and complexity. Flocculation - high; apparent attenuation 67-71%. (65-75° F, 18-24° C)

Travis

[ScienceGuy]

OK. So tonight I'll break out the TI-86 and my old pocket protector and I'll figure things out.

What about my emergency actions? I'm sure this is a pretty common question, but I'm not sure where to look. When my fermentation stops early like that, what do I do next? Do I throw more fermentables (sugar) at it or do I throw some more yeast into the primary?
Thanks