# Homebrewers Association | AHA Forum

## General Category => Kegging and Bottling => Topic started by: yaleterrace on November 20, 2010, 09:35:35 am

Title: krausen equation
Post by: yaleterrace on November 20, 2010, 09:35:35 am
Can anyone help me out with a real and accurate krausen equation?  I brew ales and would like to bottle and keg referment without the use of refined sugar.  I would be adding unfermented wort to a fully fermented batch, none of the potentially more complicated lager techniques.  I found the following formula, but I';m not sure it's what I need:

Vp/Vb = SGb/SGp x Cv/(2.44 x SGb x SGp x F - Cv)
Title: Re: krausen equation
Post by: Hokerer on November 20, 2010, 09:37:37 am
Kai's got a pretty good explanation of krausening on his wiki site...

http://braukaiser.com/wiki/index.php/Kraeusening (http://braukaiser.com/wiki/index.php/Kraeusening)
Title: Re: krausen equation
Post by: denny on November 20, 2010, 10:05:22 am
I predict that after you try it a couple times, you'll go back to sugar.  I did....
Title: Re: krausen equation
Post by: yaleterrace on November 20, 2010, 10:33:51 am
The math is definitely advanced enough that I'm not a happy camper, but I happen to be friends with a mechanical engineer who specializes in fluids, so I'll pay him in beer to help me drop the whole thing into a spreadsheet.  I really would like to get away from adding sugars and nonsense, to keep the numbers exact for ABV and such, and to keep the beer clean from refined ingredients or preservatives.  We'll see, I guess!
Title: Re: krausen equation
Post by: denny on November 20, 2010, 10:49:01 am
I felt like that at one point.  I think I tried priming with gyle about 3 times before I gave it up as inexact and showing no flavor benefits over using sugar.  I think you're fooling yourself that you'll get more exact ABV measurement, too.
Title: Re: krausen equation
Post by: jaybeerman on November 20, 2010, 10:49:41 am
I predict that after you try it a couple times, you'll go back to sugar.  I did....

I haven't tried krausening yet; did you quit due to unpredictability? I read a quote this week that I think applies to brewing.
"In theory, there is no difference between theory and practice. But, in practice, there is." (That's Jan L.A. van de Snepscheut, supplied by Quotes Of The Day)  I actually hate that quote though I know it contains truth; there are some cool techniques that really aren't that practical in the long run.  That said I'm still going to give it a whirl at least a couple times.
Title: Re: krausen equation
Post by: jaybeerman on November 20, 2010, 10:54:24 am
The math is definitely advanced enough that I'm not a happy camper, but I happen to be friends with a mechanical engineer who specializes in fluids, so I'll pay him in beer to help me drop the whole thing into a spreadsheet.  I really would like to get away from adding sugars and nonsense, to keep the numbers exact for ABV and such, and to keep the beer clean from refined ingredients or preservatives.  We'll see, I guess!

I would send you a very simple spreadsheet for free, but you already threw it out there that you were willing to pay with beer  ;D  Seriously though if you pm me I will send you a spreadsheet (maybe monday i'll have time.  I'm about to take the kid bowling)
Title: Re: krausen equation
Post by: denny on November 20, 2010, 10:54:47 am
I predict that after you try it a couple times, you'll go back to sugar.  I did....

I haven't tried krausening yet; did you quit due to unpredictability? I read a quote this week that I think applies to brewing.
"In theory, there is no difference between theory and practice. But, in practice, there is." (That's Jan L.A. van de Snepscheut, supplied by Quotes Of The Day)  I actually hate that quote though I know it contains truth; there are some cool techniques that really aren't that practical in the long run.  That said I'm still going to give it a whirl at least a couple times.

Partially unpredictability, but mainly because it was more effort for no appreciable benefit.  If I'm gonna do more work, there damn well better be a payoff for it!  But I encourage you to try it and form your own opinion.  As to not wanting to use sugar, if that was a concern I'd have to stop brewing Belgian beers!
Title: Re: krausen equation
Post by: jaybeerman on November 20, 2010, 11:03:46 am
Partially unpredictability, but mainly because it was more effort for no appreciable benefit.  If I'm gonna do more work, there damn well better be a payoff for it!  But I encourage you to try it and form your own opinion.  As to not wanting to use sugar, if that was a concern I'd have to stop brewing Belgian beers!

I hear ya on the payoff part.  My thing is that I'm kegging all my brews (ultra simple) but I wouldn't mind trying the technique out for the brews I plan on storing for very long periods of time (e.g. Barley Wine, Imp Sout, Braggot, etc).  Yeah I don't have the sugar phobia either.
Title: Re: krausen equation
Post by: euge on November 20, 2010, 12:04:27 pm
I think it makes sense if you have a brewery operation going cranking out the beer daily. A constant supply of active yeast and fresh wort and a nailed down procedure.

At the homebrew level it becomes a matter of expediency. I guess one could just prime with extract or build a "priming starter" and add that to the keg or bottling bucket?

And per Kai's write-up you still might have to add sugar anyway.
Title: Re: krausen equation
Post by: tubercle on November 20, 2010, 02:19:02 pm
Tubercle's 0.02...

1. If you add unfermented wort you are adding "sugar",  just a different type than corn or table.

2. Corn or table sugar is very predictable since it is 100% fermentable for practical purposes. Unfermented wort is a mixture of highly fermentable simple sugars and complex sugars that may or may not ferment over time. To predict the outcome you need to know what this mixture is.

3. Stick with table sugar.
Title: Re: krausen equation
Post by: lonnie mac on November 20, 2010, 02:33:18 pm
I could never try this anyway. What this gibberish means is way beyond me! :)

(http://braukaiser.com/wiki/images/a/a1/Formula_kraeusen_carbonation_metric.gif)
Title: Re: krausen equation
Post by: yaleterrace on November 20, 2010, 03:07:37 pm
you posted the metric equation for starters...
Title: Re: krausen equation
Post by: yaleterrace on November 20, 2010, 03:21:09 pm
Okay, so now everyone has the background (didn't want to get into all this):
I am brewing 10 - 15 gallon batches every 7 - 10 days (not exceeding more than 200.00 gal/yr) so I have the capacity to store and reincorporate unfermented wort.  Given that overall ambient fermentation room temperature in my home changes only +/- 5 degF per ale fermentation cycle (seasonally), I am not concerned about conditional variables as far as the differences for the gyle refermentation is concerned.  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 am not so fond of the mouthfeel of my force-carbonated batches.  Also, as I understand it, the alcohol content can be determined much more accurately with gyle refermentation since the total fermentable component of the wort is identical between the original batch and the gyle, and since fermentation has ceased post secondary fermentation, I will know the exact fractional fermentability between OG and FSG.  This means I can create a beer with no processed sugar extracts, naturally ferment it, and do so with relative ease once I can wrap my head around some numbers.  Worth it to me.
Title: Re: krausen equation
Post by: lonnie mac on November 20, 2010, 03:36:35 pm
Lot's of folks have tried this myself included.

I do have to say this though... As you stated "I am not so fond of the mouthfeel of my force-carbonated batches."

Well, that's a recipe problem then. Nothing more... If you don't like the mouthfeel, you can take care of that in the recipe. The carbonation has nothing to do with that issue other than to tell you that you have a recipe problem and you should take care of that on the front end... I couldn't brew a beer, and rely on my mouthfeel coming from bottling alone. I brew almost as much as you do, sometimes more, sometimes less... There is no way I can bottle all that beer my friend! I gotta keg!
Title: Re: krausen equation
Post by: tschmidlin 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 . . .
Title: Re: krausen equation
Post by: tubercle 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.
Title: Re: krausen equation
Post by: Kaiser 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

Title: Re: krausen equation
Post by: yaleterrace 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?
Title: Re: krausen equation
Post by: bonjour 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.
Title: Re: krausen equation
Post by: denny 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.
Title: Re: krausen equation
Post by: jeffy 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.