Draft Carbonation - Modified Slam/Shake vs. Gradual Carbonation

drew's picture

It's happened to us all - too many kegs, not enough time left to "properly" carbonate your beer before it needs to be served. Who knows, maybe you have a party or club meeting. Maybe you just need a beer, damnit. 

The old school proper carbonation method involved looking at a carbonation table. You set your regulator to the appropriate p.s.i. for your temperature and desired carbonation level, hook the gas up to your keg and patiently wait 10-14 days. Then you pull the gas, relieve the pressure and serve a bright sparkling glass of brew.

But many homebrewers, of course, just can't wait and so they follow the other "traditional" advice - chill your beer, set the regulator to 30 p.s.i., hook up the gas and set the keg on its side and shake for 5-10 minutes. Right the keg, pop the pressure and serve.

The slame and shake is definitely a less accurate methodology, so I've used a combination method for years to get the benefits of both. Basically, I choose the appropriate psi on the table, set my regulator to that level+1-2 p.s.i. and then rock the keg until the gas stops burbling (~5-15 minutes). At that point, I let the keg settle and release the pressure and prepare to serve.

So does it work? I think it does, but there's a belief that any of the agitation methods damage foaming qualities of the beer. Let's test it out and let's see if the method works and if tasters notice a difference between them!

Experiment Status: 



Does a modified slam and shake method result in a beer observably different than one done by the longer sit and wait methodology?


There will not be observable difference between the two beers

Brewing Sessions Needed: 


Special Equipment/Process: 

  • This will be a draft project, so we're asking that the beers be served on draft (or from growlers fresh filled from draft)

Special Observations: 

  • Record the beer temperature, psi, and time setting at which you carbonate both kegs.
  • After the triangle test - ask the testers for their observations about the beer foam and carbonation levels.
  • A further observation - is there an additional bite to the "slam" carbonated beers? Some report a sharper character as a hallmark of the technique.

Experimental Procedure: 

  1. Brew enough TBD Recipe to split evenly between two kegs (e.g. brew 5 gallons and split evenly into 2.5 gallons kegs). Record the Original Gravity. Pitch equal sized yeast pitches for all the kegs.
  2. Ferment all batches in the same space and under the same conditions, especially temperature. Match the fermenters and other equpment.
  3. After fermentation subsides, record the length of fermentation and the final gravities.
  4. Package the two beers in two separate kegs. Chill both kegs to the same temperature.
  5. Add 1-2 psi to the regulator from the settings necessary to hit 2.5 volumes of carbonation according to your table/chart/software. Attach the gas to the "slam" keg and set it on it's side and rock back and forth for 5-10 minutes or until the gas stops audibly bleeding into the keg on shaking.
  6. For the "gentle keg", reset the regulator to the appropriate psi to achieve 2.5 volumes of carbonation for the beer storage temperature and hook to the "gently keg". Let sit for 10 days. 
  7. Remove the gas and bleed the pressure on both kegs and set them to serving pressure.
  8. Perform a triangle test and record the results
  9. Ask the testers for their observations on the samples. DO NOT Reveal the Difference between the samples
  10. Discuss the results and record any further observations

Recipe Link: 

Further Exploration Paths: 

Does the observed behavior change based on carbonation level?
Do adjuncts like wheat affect the heading? (What about hops?)
Shake/Slam experiment

Flood the keg to be shook with 10 psi to seat the lid, but disconnect the gas. Set the regulator to the appropriate psi to achieve 2.5 volumes of carbonation for the beer storage temperature. Let sit for 10 days.

Did you mean disconnect the gas?  

After 10 days, remove the gas from the first keg and add 1-2 psi to the regulator. Attach the second keg and set it on it's side and rock back and forth for 5-10 minutes...

I always thought the idea was to hit it with something like 20-30PSI and then rock it.


This is an experiment I think I'll be able to do(as long as it's not a saison wink)

drew's picture
Will clarify the first -

Will clarify the first - problem with the second and why I'm not saying let's do the traditional slam/shake - way, way too variable and can't positively say people will get it right. So let's test the modified "more accurate" form and see if there's the heading/carbonation differnece people claim from the slam and shake.

ejpejp77's picture
Traditional Crank (Slam) and Shake - Carbonic Off Flavor

In addition to foam quality, I've read somewhere that people are afraid of an off flavor or "bite" that results from quick high pressure carbing.  The only time I did this was with an Apple Beer so if the off flavor was cidery I never would've noticed it.  It would be interesting if anything flavor or mouth feel differences are detected.

drew's picture
Will add to the observations

Will add to the observations