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Old 10-27-2007, 05:28 AM   #1
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Default Water Chemistry - Hardness, Alkalinity, and Additions

I like chemistry, so I've been working on building up (or down) my local water to suite my brewing purposes. I downloaded our local water report to get a baseline and began calculating additions from there.

Preface: this question/observation only concerns additions affecting hardness and carbonate levels. Sulfate, sodium, chloride, and other taste-affecting ions aren't really covered b/c that's not part of my question.

I've listed below the traditional brewing waters with some chemical data. By using the bicarbonate (HCO3), calcium (Ca), and magnesium (Mg) concentrations, one can calculate the alkalinity (in equivalents of CaCO3) as well as the hardness (also in equivalents of CaCO3). Please note that neither of these are concentrations of CaCO3. It's just a way of expressing the data.

Going on...
Alkalinity is (in tap water) primarily a function of the bicarbonate (HCO3) and carbonate (CO3) concentrations. These are the conjugate bases of carbonic acid and part of the carbonic buffering system. The more carbonate and bicarbonate you have, the more acid can be introduced without changing the solution pH as much... hense... the term buffer.

Hardness relates to the calcium (Ca) and magnesium (Mg) concentrations. These ions help to counteract the basic buffering properties of carbonate and bicarbonate by becoming associated with them via charge-charge interactions, not allowing them to accept more H+ molecules (acid).

Here's my observation/question.
Since higher alkalinity helps neutralize acids, and hardness helps counteract that effect.... shouldn't the ratio of hardness to alkalinity be a good design variable? (given the fact that acidity and grain roast level are roughly proportional)

To test this, I charted the traditional brewing waters below in order of this ratio. It seems to make sense that the lowest hardness to alkalinity ratio is Dublin. That means that Dublin should have more alkalinity per hardness and therefore be able to neutralize more acid. And, sure enough that water naturally makes the darkest beers well (using dark roasted acidic grains). The reason that the acid needs to be neutralized somewhat is to keep the mash pH near it's sweet spot between 5.0 and 5.5.



So... I've started building my water based on the hardness to alkalinity ratio. And so far so good. Any thoughts? or flames? It's okay, my feelings won't be hurt. Just looking for input/dialogue.

Cheers!

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Old 10-27-2007, 05:44 AM   #2
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You are way above my IQ.

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Old 10-27-2007, 03:14 PM   #3
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Interesting, I don't think I've heard anyone really talk about brewing water as a ratio of alkalinity and hardness. I would be interested to see how this system goes in the mash tun. I don't know much about water chemistry, but my understanding was that the actually quantities of Ca, Mg and bicarbonate are the greater concern.

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Old 10-27-2007, 03:45 PM   #4
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Sounds like you understand it well. This may help in determining how you can adjust your water for certain beer styles. Palmer uses nomographs and there's also a spreadsheet, but I'm not certain it's a simple ratio like you said. I think the formula is a little more involved. You could probably reverse engineer the spreadsheet to figure it better.

http://www.howtobrew.com/section3/chapter15-3.html

Here's an example of a nomograph.

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Old 10-27-2007, 04:28 PM   #5
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uno momento...

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Old 10-27-2007, 04:50 PM   #6
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Quote:
Originally Posted by thomcat333
I like chemistry
clearly. nerd.


Quote:
Originally Posted by thomcat333
Since higher alkalinity helps neutralize acids, and hardness helps counteract that effect.... shouldn't the ratio of hardness to alkalinity be a good design variable? (given the fact that acidity and grain roast level are roughly proportional)
Yes, precisely, as this is a ratio of the acid dissociation equilibria for carbonic acid to the solublity equilibria of CaCO3.

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Originally Posted by thomcat333
To test this, I charted the traditional brewing waters below in order of this ratio. It seems to make sense that the lowest hardness to alkalinity ratio is Dublin. That means that Dublin should have more alkalinity per hardness and therefore be able to neutralize more acid. And, sure enough that water naturally makes the darkest beers well (using dark roasted acidic grains).
Which makes sense. The pKa of the first proton dissociation for carbonic acid is 6.4. In order to obtain adequate buffering capacity you will need to have an overall aqueous equilibria such that there's enough free carbonate to buffer between CO3 and HCO3, while enough CaCO3 present to not bind the carbonate and not so much free carbonate in excess to CaCO3 as to form too much bicarbonate, thus skew your buffering capacity (your alkalinity equilibrium). Groovy.

Furthermore, you can't have all your Calcium bound as a carbonate precipitate since free Ca2+ ions are absolutely essential to slabilizing alpha amylaze activity (your hardness equilibrium).

From what I understand, you ratio directly relates these two, which is a neat idea and guideline. It is sure a hell of a lot easier than combining all the Keq, Ka, and Ksp equations. It is a guideline though, a very general one, since there are many, many, many more competing equlibria that occur throughout the mash. And as soon as you add heat to this system, you're going to be releasing CO2, which will further screw up the estimates.

Now, I just read through that and thought it out aver being up till 3am drinking. It's 9am now, so let that be a caveat if my logic is in err, or is just plain drunken rambling. I await the dissenting opinion. My head hurts, I'm going back to bed. Cheers.
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Old 10-27-2007, 04:56 PM   #7
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You are definitely on the right track here -- the balance of hardness and alkalinity is the key to understanding the effect of your water on mash pH. But instead of taking a ratio of the numbers, it is more common to difference them. When expressed in equilavents, the hardness and alkalinity counter-act one another in the mash. So, it is common to look at what is 'left over'. This is termed 'residual' alkalinity, and it is simply your alkalinity minus your hardness. If the value is positive, then you have enough alkalinity left in your water to raise the pH of your mash. If it is small or negative, then your water won't raise the pH, and you will have problems mashing dark, acidic grains.

Palmer's nomograph is a handy tool for checking this. Conceptually, it is somewhat similar to your hardness/alkalinity ratioing. But the actual math behind the nomograph uses a difference equation (alkalinity - hardness).

Your ratios will work, too, although the scale will be non-linear so it is not as convenient. The general rule of thumb would be that if your ratio of hardness/alkalinity is less than 1, then your water will have some ability to buffer an acidic mash. If it is over 1, then it will not and you are best brewing lighter beers or adding salts for darker (i.e. more acidic mash) brews.

A couple of notes: First, I am not sure how you calculated your alkalinity, but it does not appear to be in the same units as your hardness (i.e. CaCO3 equivalents). They should be to do your ratioing. Second, if you flip your ratio (i.e., alkalinity/hardness) you might find this more useful as most numbers will end up being greater than one, and the magnitude of the number will indicate the buffering capacity of your water.

Cheers!

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Old 10-27-2007, 05:17 PM   #8
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Check out the wiki, some good stuff on there.
I've never tested my water, I've never adjusted it.

I think my beer is better then most of the big brewery stuff and equal to the good craft stuff available.

Plus that stuff makes my head hurt.

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Old 10-27-2007, 10:33 PM   #9
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Yep Palmer's nomograph operates like you are saying... the difference of relative hardness and alkalinity. How 'bout that?

As for the hardness numbers, I had calculated total hardness rather than relative, which seems to be more appropriate. I'll have to change that. I'll also have to change from a ratio to a difference. Then my addition spreadsheet should be pretty spot on.

Next question:
Based on the Palmer nomograph, it looks like you will need really hard water (with very low alkalinity) to have an all-base malt mash near 5.3. Do most people just mash higher and not feel any ill effect? The color spectrum just above the pH line shows lighter beers around 5.6... What's the deal? I've read a bit about the acid rest from the history of Pilseners, but I'd rather not do that.

Oh, and yes I'm a bit of a nerd. Gotta love it.

Cheers!

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Old 10-28-2007, 03:34 AM   #10
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I just read through most of this thread and there is now smoke coming out of my ears. Thanks for frying the last few brain cells.

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