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-   -   Totally Confused About Residual Alkalinity (http://www.homebrewtalk.com/f128/totally-confused-about-residual-alkalinity-345493/)

chally 08-03-2012 06:48 PM

Totally Confused About Residual Alkalinity
 
I'm just getting started down the custom water profile path. I've read the primer, and I think I get the basics with respect to stuff like mash pH and chloride:sulfate ratio. I don't have a great source for RO or distilled water, so I try to make my tap water work (with some minor additions, and dillution where really needed).

Throughout this process, however, I keep bumping into the notion of residual alkalinity and the information seems to be all over the map. Some say it's important, some say it's not.

I recently tried to design a water profile for an oatmeal stout using a target profile from the Bru'n Water Calculator. It ended up saying that my mash pH was too high (~5.6) AND my RA was too low (~48). I can't figure out how to save one without sacrificing the other. I suspect it's the RA that has to be sacrificed, but I'd like to know what I'm sacrificing and what the impact on the beer will be.

Can anyone just cut to the chase and complete the following sentences:

Residual alkalinity is [not/somewhat/very] important. It should be the [first/second/third/last] thing you care about when setting your water profile, behind __________ and ahead of _______. If it is too low for your style, then _____; if it is too high for your style, then _____.

GnarlyBarleyBrewing 08-03-2012 09:12 PM

Wow, I am facing the exact same problem you are. I sort of posted it right before you did; you just did a better job of explaining it. When I get my PH of 5.55 I get a -75 RA. I can’t find any info on low RA. I’m starting to think it’s not a problem as long as your PH is good but who knows. I’ve been researching this for 2 days now and haven’t found one thing referring to this issue.

yso191 08-03-2012 10:06 PM

Maybe you've already come across this, but I found it informative:
Steve

mabrungard 08-04-2012 12:45 AM

Quote:

Originally Posted by chally (Post 4303177)

I recently tried to design a water profile for an oatmeal stout using a target profile from the Bru'n Water Calculator. It ended up saying that my mash pH was too high (~5.6) AND my RA was too low (~48).

I'm hoping that Bru'n Water isn't trying to guide you with a recommendation for RA. To my knowledge, there is nothing in the program that recommends a certain RA. Alkalinity and RA are the main factors that are contingent upon the actual grist used. Those water profiles in Bru'n Water include recommendations for bicarbonate content that are only first guesses. Since alkalinity and RA are directly a function of bicarbonate content, that means that they are first guesses too. The brewer will adjust bicarbonate content to better fit their actual grist acidity.

Forget about RA all together. The only thing that matters is the mash pH. RA is only a rough corollary for mash pH response and its clouded by too many other factors to be truly useful as a brewing parameter.

ajdelange 08-04-2012 12:56 AM

Residual alkalinity was cooked up by Paul Kolbach during WWII as a means of comparing brewing waters and for that it is quite useful. It's utility for this purpose is enhanced by plotting water characteristics on a chart like the one at http://www.pbase.com/agamid/image/57446374. Trying to hang too much significance on it is likely to lead one astray. Brewing water chemistry is intricate if not complex and many of us, home brewers that is, grasped at in desperation ascribing to it much more utility than it really has.

yso191 08-04-2012 05:54 PM

Interesting.

mabrungard & ajdelange: I certainly don't know enough to debate the matter with you, as I am just beginning the learning process. So I am just hoping for some clarification. The video I posted is certainly in the category of 'prompting a lot of utility' to the concept. Particularly at 24:25 he introduces an experiment he did with two beers, each brewed at two RA's. His conclusion was that the beers brewed at the right RA were complex, but the beers brewed at the wrong RA were one dimensional.

A pretty attractive result. I'd sure rather brew complex, multi-dimensional beers. So where am I not understanding him, or is he overstating something? Thanks,

Steve

yso191 08-04-2012 06:26 PM

Sorry for asking the above question, I should have read first. I believe I have found the answer in section 2.4 of: https://sites.google.com/site/brunwater/water-knowledge . Thank you for that great resource Martin! (and for the EZ Water spreadsheet - an awesome tool)

Steve

mabrungard 08-04-2012 06:59 PM

Quote:

Originally Posted by yso191 (Post 4305142)
Interesting.

Particularly at 24:25 he introduces an experiment he did with two beers, each brewed at two RA's. His conclusion was that the beers brewed at the right RA were complex, but the beers brewed at the wrong RA were one dimensional.

Oh, I agree with that result. The problem is with the connection to the 'right RA'. Its actually a connection to the proper mashing pH and RA is only a loose corollary to mash pH since the effect of the mash composition plays such a big part. Any connection between the appropriate RA and beer color is filled with problems.

tochsner 08-08-2012 06:08 AM

Quote:

Originally Posted by mabrungard (Post 4305227)
Oh, I agree with that result. The problem is with the connection to the 'right RA'. Its actually a connection to the proper mashing pH and RA is only a loose corollary to mash pH since the effect of the mash composition plays such a big part. Any connection between the appropriate RA and beer color is filled with problems.

Okay, this will probably only muddy the waters. I am planning water adjustments in Bru'n Water for a Marzen I plan for this weekend.
Using the amber malty profile it suggests an RA of 45.
After some Gypsum and Calcium Chloride additions my estimated mash PH is 5.3 and the finished water profile shows an RA of -18.
If I add a little baking soda I get the RA to the 45 and my estimated mash PH is 5.6.
Heres the question, do I or don't I care what the RA is?

ajdelange 08-08-2012 11:28 AM

Not really. What you care about is that the mash (and subsequent) pH's are correct and that the calcium, chloride and sulfate levels are proper for the flavor/body profile you want.

As pointed out in #5 the value of RA is in its ability to roughly compare raw waters. If you look at the chart referenced in that post you will see what famous brewing cities have which RA's and, knowing the styles of beer brewed in those cities, have an idea as to what your water would be suited for without treatment under the presumption that 1. The chart is right about the cities' waters (it isn't in many cases) and 2. That the brewers brewed with the water for their cities without treatment (they didn't in many cases). Furthermore, you can get a rough idea as to what you must do, in terms of alkalinity reduction/increase or effective hardness reduction/increase or both to render your water like that of a particular city and this, presumably to make it more suitable for brewing the beer associated with that city. But, as noted above, it isn't enough to know what the water coming out of a Burton well is like to make good Burton style beers. You must know what the brewers of Burton,for example, did to it, if anything, to make the water they had more suitable for brewing (they decarbonated it by heating).

RA has a mathematical definition based on the alkalinity, calcium and magnesium content so it can be calculated whatever you do to the water as long as you know the alkalinity, calcium and magnesium. And this is what the spreadsheets do. But beyond comparing raw waters the RA doesn't really tell you much as the amount of acid contributed by calcium is, for reasonable amounts of calcium, small compared to the amount of acid you must typically add as acid malt, CRS, lactic acid, sauermalz etc.

John Palmer noted the correlation between beer styles' colors and the RAs of the raw waters that were associated with the breweries that produced them. The home brewing world assumed that this correlation was much tighter (higher r) than it really is and tried to make color a design parameter. I think enough water is over the dam, so to speak, at this point to have shown that this isn't a good approach and people are starting to back off on RA as the backbone of a beer design. But for seeing how your water compares to Dublin's an RA chart is still a useful tool. If you are mathematically inclined you can think of the RA chart as the projections of multidimensional water vectors onto a 2 dimensional space.

I should point out that at one time I too put a lot of weight on RA. Engineers are always looking for some figure of merit to hang their hats on and RA seemed to me, as it has to many others, to have lots of promise. And it is, of course, still valuable - just not as valuable as some formerly thought (and I guess still do).


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