### Author Topic: krausen equation  (Read 6138 times)

#### tschmidlin

• I must live here
• Posts: 8198
• Redmond, WA
##### Re: krausen equation
« Reply #15 on: November 22, 2010, 02:07:30 am »
I agree with all of the people who say you are wasting your time, but it's your time so here are some rough calculations . . .

The easiest way to figure it out is to figure out how much corn sugar you would add.  If you're adding 3/4 cup, that's around 5 oz by weight.  Corn sugar gives 46 points per pound per gallon, so you're adding 5/16*46/5 =  2.875 points per gallon.  If you are really that rigorous, monitor your beers well, and brew regularly enough to know exactly where the beer will finish, then you can just keg when your beer is 3 points above the FG and let it carbonate.  Some experimentation will let you dial it in.

If that's too risky for you, then just save some of your batch in the fridge or freezer until it is done fermenting.  Once you know the OG and FG you can calculate the RDF to calculate how much of the unferemented wort to add to the beer at kegging, it's pretty straightforward algebra to get you close.  This formula will get you in the ballpark, where %Sc = % sugar (current), %A = ABV, and %So = %sugar (original).

%Sc =(1.4*%So - 0.21*%A - 1)/0.4

You use the current %Sc to calculate the RDF . . .

RDF = (%So-%Sc)/%So

Once you know your RDF you can figure out how much to add.  If your RDF is 55%, which is not unreasonable, and the OG was 1.060, you can assume you're getting 33 points from each gallon of wort.  You need 2.875 points per gallon, so . . .

33* Va + 0*Vo = 2.875*(Vo+Va)

Where Va = added volume and Vo = original volume

Solve for Va . . . . Va ~= .1 * Vo

So you should add about 1/2 gallon of your unfermented beer to 5 gallons to carbonate it.

I don't do this.  I hope this helps - the theory is sound, but I may have muffed the math along the way . . .
Tom Schmidlin

#### tubercle

• Senior Brewmaster
• Posts: 1639
• Sweet Caroline
##### Re: krausen equation
« Reply #16 on: November 22, 2010, 06:01:28 pm »
Understood very little but read it anyway, twice.
Went and got another beer and opened the cabinet to make sure the bag of sugar was still there.

It is

Smiled and continued reading the forum.
Sweet Caroline where the Sun rises over the deep blue sea and sets somewhere beyond Tennessee

#### Kaiser

• Senior Brewmaster
• Posts: 1797
• Imperial Brewing Geek
##### Re: krausen equation
« Reply #17 on: November 22, 2010, 09:16:13 pm »
I would also like to eliminate the use of refined sugar us in my processes.  (So I take pride in turning malted barley into sugar.  So what?)  As it is now, I have almost exclusively employed dextrose as a refermentation fermentable, but recently having acquired the total apparatus for kegging multiple batches,

I welcome this spirit.

Quote
I am not so fond of the mouthfeel of my force-carbonated batches.

Be careful with this statement around here . You'll nee some data to back that up.

However, I myself keg most of my beers and carbonate them naturally. One main advantage is that I don't have to pay extra for the CO2 I'm using and I don't have to hook them up to a CO2 tank just to carbonate them.

and the Kraeusen article that was posted earlier. There is also a link to a spreadsheet on that article. This is the spreadsheet I'm using and it should be mostly bug free.

The fast ferment test can be used to estimate the FG of the beer in a way where you don't even have to let the beer finish fermenting before you start carbonating it.

However, you are in a situation where you don't have to be as accurate as you have to be when you are bottling. As log as you have enough residual sugar in the beer to carbonate the beer you can always vent any excess CO2. This excess CO2 will show up as excess pressure. Search the web for Spunding Valve. This is a pressure sensitive blow-off that you can adjust to blow off excess CO2 during the carbonation process.

Kai

#### yaleterrace

• 1st Kit
• Posts: 11
##### Re: krausen equation
« Reply #18 on: November 26, 2010, 08:00:10 am »
Quote
I am not so fond of the mouthfeel of my force-carbonated batches.
Be careful with this statement around here . You'll nee some data to back that up.
[/quote]

Am I at risk of some unbearable humiliation, or is it something else?  Flavor-wise I tend to prefer the CO2 in my beer to be the 'dirty' fermentation exhaust as opposed to store-bought gas.  This, I hope, you would concede to.  As far as mouthfeel goes, am I really having a sensory malfunction as you seem to suggest, or does the velvety-smooth force-carbed draft I've been pouring really have the same body profile as the bright, clean and sharp carbonation from my bottle conditioned beers?  For the record, I did a horizontal tasting with friends of an IPA that I split between keg (force) and bottle (dextrose), so perhaps my experiment had sloppy variables, but the mouthfeel of force-carbed draft seems creamier than refermented draft, and I don't like creamy.  Thoughts?

#### bonjour

• Senior Brewmaster
• Posts: 1791
• Troy, MI, 37mi, 60.9deg AR
##### Re: krausen equation
« Reply #19 on: November 26, 2010, 08:40:42 am »
A blind triangle test with brews that you don't know will give you a better determination if this is perception of knowing the beer or perception of fact.  Try with multiple brews.

Many on this board have determined that with a triangle test, what they had previously though wasn't so.

I'm not saying one method is better than the other, just that the only way to determine what you truly perceive is to perform a blind triangle taste test.
Fred Bonjour
Co-Chair Mashing in Michigan 2014 AHA Conference in Grand Rapids, Michigan
AHA Governing Committee; AHA Conference, Club Support & Web Subcommittees

Everything under 1.100 is a 'session' beer

#### denny

• Retired with too much time on my hands
• Posts: 27233
• Noti OR [1991.4, 287.6deg] AR
##### Re: krausen equation
« Reply #20 on: November 26, 2010, 09:02:14 am »
For the record, I did a horizontal tasting with friends of an IPA that I split between keg (force) and bottle (dextrose), so perhaps my experiment had sloppy variables, but the mouthfeel of force-carbed draft seems creamier than refermented draft, and I don't like creamy.  Thoughts?

I certainly wouldn't rule out something you did as opposed to the process itself.  You're certainly entitled to your opinion, but many people have gone through the same process and found opposite results.  Don't be so quick to discount them.  Remember, 2 is CO2, no matter what the source.
Life begins at 60.....1.060, that is!

www.dennybrew.com

The best, sharpest, funniest, weirdest and most knowledgable minds in home brewing contribute on the AHA forum. - Alewyfe

"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts." - Bertrand Russell

#### jeffy

• Official Poobah of No Life. (I Got Ban Hammered by Drew)
• Posts: 4235
• Tampa, Fl
##### Re: krausen equation
« Reply #21 on: November 26, 2010, 09:58:29 am »
Quote
I am not so fond of the mouthfeel of my force-carbonated batches.
Be careful with this statement around here . You'll nee some data to back that up.

Am I at risk of some unbearable humiliation, or is it something else?  Flavor-wise I tend to prefer the CO2 in my beer to be the 'dirty' fermentation exhaust as opposed to store-bought gas.  This, I hope, you would concede to.  As far as mouthfeel goes, am I really having a sensory malfunction as you seem to suggest, or does the velvety-smooth force-carbed draft I've been pouring really have the same body profile as the bright, clean and sharp carbonation from my bottle conditioned beers?  For the record, I did a horizontal tasting with friends of an IPA that I split between keg (force) and bottle (dextrose), so perhaps my experiment had sloppy variables, but the mouthfeel of force-carbed draft seems creamier than refermented draft, and I don't like creamy.  Thoughts?
[/quote]

Your experiment may be flawed because you have no way of knowing if both samples are carbonated to the same exact volume.  There may also be flavor contributions from the sugar added and the alcohol produced by bottle conditioning.  Like Denny says, CO2 is CO2.
« Last Edit: November 27, 2010, 11:30:09 am by jeffy »
Jeff Gladish, Tampa (989.3, 175.1 Apparent Rennarian)
Homebrewing since 1990
AHA member since 1991, now a lifetime member
BJCP judge since 1995