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Rescuing uncarbonated or undercarbonated beer - An Experiment

A long time ago, I began to notice that when I brewed beers over 9-10% alcohol by volume (ABV) that they tended not to carbonate in the bottle.  It became a rule of thumb for me to always include bottle conditioning yeast (either CBC-1 or champagne yeast) any time I brewed a beer over 9%.  I forgot to do that with a beer that came out at 10.9%, and it failed to carbonate.  I learned with that beer that by inverting the bottles daily for a week to rouse the yeast inside, I could achieve carbonation.

When I brewed a batch of beer intended to replicate Dogfish Head's Palo Santo Marron, I decided to take a chance and not dose it with bottle conditioning yeast either.  After weeks in a warm location, there was virtually no carbonation, even using the bottle-inversion trick.

For another two weeks, I increased the temp to 80F and did a daily inversion of the bottles, while also rotating them around the space inside the cooler to ensure that every bottle spent time in every temperature condition in the cooler. Again, there was no significant carbonation.

Today I decided to see if I could rescue the beer without contaminating it.

The goals of this experiment were:
  • Determine if pitching active bottle conditioning yeast into a flat bottle of beer is by itself enough to carbonate that beer.
  • Determine if pitching active bottle conditioning yeast along with additional carbonation sugar is enough to carbonate the beer.
  • If one or both of the above is true, determine the minimum amount of yeast you would need to add to a bottle to achieve carbonation.
To test the experiment, I did the following:
  • Removed exactly half the bottles from my temperature-controlled cooler and brought them to my bottling table.
  • Boiled water and rehydrated a packet of CBC-1 Cask and Bottle Conditioning Yeast along with about a tenth of a teaspoon of yeast nutrient and a tablespoon of Brewer's Crystals to ensure viable, active yeast was being used.
  • Opened a fresh package of Cooper's Carbonation Drops.
  • Sanitized enough bottle caps to re-cap the bottles used for the experiment.
Once the yeast proved to be active, I followed the process below for each bottle:
  • Uncap the bottle and drop in zero (0) to two (2) carbonation drops.
  • Using a sanitized disposable pipette, suck up a pipette full of yeast slurry and squirt it into the bottle.  I used as few as one squirt to as many as six squirts.
  • Immediately re-cap the bottle using a sanitized cap and my bench capper.
  • Dry off the cap and mark it with a Sharpie to indicate the number of carbonation drops inserted (0 to 2) and the number of yeast doses inserted (1 to 6).
  • Return the bottles to the temperature controlled cooler along with the original (control) beers.
As I write this sentence (on October 8, 2017) the experiment has just begun.  My plan from this point forward is as follows:
  • For the next two weeks, open the cooler and invert each bottle to ensure that the yeast is roused and moved through the beer. Hopefully this will give me the best chance at carbonating the beer.
  • After two weeks, take a bottle of the "most dosed" beer out of the cooler and refrigerate it overnight to chill to drinking temperature.  Open the beer, pour it into a glass, and observe its carbonation level.  Hopefully it will achieve a decent (if not overly high) level of carbonation.
  • If that "most dosed" beer still isn't carbonated, give it another week of 80F and rousing and try again.  If that doesn't work, I'll give up and force carbonate the beer a gallon at a time in my Man Can growler.
  • Assuming that this "most dosed" bottle does carbonate as I hope, chill a bottle of all the other "dosage levels" of sugar and yeast.  Open those to see what level of carbonation drops and fresh yeast achieved a nice level of carbonation in the beer.
  • Once an ideal number of carbonation drops and yeast doses is identified, remove the rest of the bottles from the cooler and dose them appropriately, following the same process of inverting daily and keeping the temp under control.
I'll be back to update this article later in the month when I have tested the first bottle.


10/15/2017:  I removed one of the bottles from the hot box and chilled it to drinking temperature. This particular bottle had 2 carbonation drops and 4 pipette doses of yeast added before re-capping.  Prying off the cap yielded a definite release of CO2.  Pouring into a glass also yielded a thin head that dissipated quickly along with a nice amount of carbonation in the glass.  While I will want to test some of the other bottles to see if I can identify a mix of carbonation drops and yeast addition that provides my desired amount of carbonation, The experiment was a success!

Two carbonation drops and four doses of yeast, one week of conditioning

10/21/2017:  I placed a bottle of each "dosage" of yeast and sugar into the refrigerator last night to try to see what the optimal level of sugar and yeast additions would be for this beer. That will enable me to properly dose the rest of the batch (which is still flat) and achieve a desirable carbonation level.  I'll share more on this as I open and test each bottle.

10/22/2017:  Below is a photo of a 12-ounce bottle of the previously-uncarbonated beer after two weeks in an 80F box, when treated with only 3 doses of yeast and no additional sugar, and being poured hard into a glass.

No carbonation drops, but 3 doses of yeast
Zero carb drops, 3 doses of yeast, approximately 14 days of conditioning
10/28/2017:  Below is a photo of a bottle with two doses of yeast and no added sugar.  Poured hard into the glass it had some carbonation, but not as much as the previous bottle which had three doses of yeast.  So far, the three-dose version looks better to me for this beer.

Two doses of yeast, no carb drops, 20 days of conditioning

11/12/2017:  Below is a bottle dosed with one pipette of yeast and 1 carbonation drop.  While it did provide some carbonation, the level is considerably lower than the previous bottle opened, which had two doses of yeast and no additional sugar. This leads me to think that dosing the beer with fresh, active yeast is more important than adding sugar.  This bottle has had longer to condition and carbonate than any of the above, and is the flattest of them all.

1 carb drop, 1 dose of yeast, 30+ days of conditioning

11/21/2017:  I mixed up some CBC-1 yeast and got it to start actively fermenting. Once it was going well, I gathered all my remaining "un-dosed" bottles together and gave each three pipettes of yeast, which was enough in the test cases to give me a good carbonation level.  I then re-capped each bottle and returned it to the 76F "hot box" (well-insulated cooler with a fermwrap heater inside and a temperature controller) to carbonate.  Last night, after a week in the hot box, the beer was properly carbonated and ready to drink.


Following are my recommended guidelines regarding carbonation of bottled homebrew. As with any recommendation, you should test these and if your experience dictates differently, adjust these recommendations to meet your unique requirements as a home brewer.

  • For beers above 10% ABV, I recommend rehydrating a dry yeast like Danstar CBC-1 or a champagne yeast.  Pitch this into the bottling bucket along with your priming sugar. Bottle the beer as normal. This should ensure good carbonation.  Below 10%, you should not need to do this unless you've really stressed the yeast or it's a variety that flocculates exceedingly well.
  • If you encounter a beer below 10-12% ABV that doesn't seem to be carbonating, try rotating the bottles upside down nightly for at least one week. On night 1, sit the bottle upright as you normally would. On night 2, flip the bottle so it's sitting on its cap/crown. On night 3, return the bottle to the normal upright position - and so on for at least a week. Then chill and open a bottle to see if it has carbonated.
  • If, after 1-2 weeks of "bottle flipping" as described above, the beer is still not carbonated, dose the bottles with fresh yeast. I recommend the process below:
    • Boil 4-6 ounces of water to sterilize it. While boiling, add about a half-teaspoon of DME or Brewer's Crystals. If you don't have those, corn sugar might work OK too. Add a tiny pinch of yeast nutrient as well. I literally used what I could pinch between two fingers without going overboard.
    • Allow the above mixture to cool to 95F or whatever temperature the yeast manufacturer recommends for rehydration.
    • While this is going on, prepare your bottle capper, sanitize an appopriate number of bottle caps and a bottle opener. Have all the bottles of flat beer ready to go.
    • Add the dry yeast and leave it alone. Check it every few minutes. When you see foaming or krausening happening on top of the mix, you're ready to begin.  Stir the mixture to ensure that it's got an even mix of yeast, nutrient, and sugar
    • For each bottle, uncap it, use the pipette to squirt three shots of yeast into a bottle, then re-cap it with a sanitized cap.
    • When you've completed all the bottles, turn them upside down, then right-side-up, etc. a few times to get the yeast mixed with the beer in the bottle.
    • Each day, rotate the bottle. On one day, have the bottle on its crown/cap. The next, set the bottle upright normally. This will give you the best chance of carbonation.
    • If you get any yeast-related off-flavors after a week (and I don't think you will), leave the bottles out at room temperature for another week or two to allow those to dissipate.


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