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Old 04-21-2009, 04:17 PM   #1
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Default Water hardness and pH

So I am delving into various books and other resources regarding water chemistry in brewing. I decided to ask some things here as well to cover some more bases. What is the relationship between hardness and pH? Are there any specific ions which relate to or affect hardness and pH both. I understand pH is a measure of acidity and hardness is a measure of dissolved ions in the water. Basically I am not yet understanding if hardness and pH are totally seperate things or if raising/lowering one will affect the other. Thank you for any responses.

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Old 04-21-2009, 04:20 PM   #2
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As I have come to understand they are seperate but entertwined. I skipped chemistry and all this reading means without at least some chemistry basics.

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Old 04-21-2009, 04:25 PM   #3
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There are a couple of recent podcasts on water adjustment and how it effects brewing.
Brew Strong

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Old 04-21-2009, 05:01 PM   #4
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It is all sort of intertwined. I'm no expert by any means and must tread carefully or I'll say something untrue (or at least misleading) but here goes. I don't really worry about the pH of the water itself per se...but I am interested in and do measure the wort pH. I'm more interested in the hardness and alkalinity of the water itself. Alkalinity and pH are not the same thing. The alkalinity of the water and it's hardness will determine the mash pH (along with the grain bill). These two terms can be used to determine Residual Alkalinity.

Go to Palmer's site and read Chapter 15. He defines Residual Alkalinity which is very helpful in predicting mash pH. Light beers need low residual alkalinity so the mash pH will be low enough and dark beers need high residual alkalinity to counter the acidic dark malts. The mash pH should be the same regardless of style.

To reduce residual alkalinity you need to either reduce alkalinity or increase hardness...or both. To increase RA you need to either increase alkalinity or reduce hardness...or both. The nomograph at the bottom of section 15.3 in How to Brew illustrates this very well.

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Old 04-21-2009, 06:59 PM   #5
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I guess another part to this question would be, If you were to do an acid rest to acidify the mash, would this be affected in any way by any ions or softness/hardness of the water or would the acidification affect the ways the ions act in the final beer or hardness/softness? I'm just trying to understand where the links are in the pH and water hardness/ion relationship.

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Old 04-22-2009, 05:27 PM   #6
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As far as I understand, the ions & the residual alkalinity contribute to what the mash pH WOULD be with a given grist. Doing an acid rest or changing the grist would then adjust that mash pH.

Also, remember - pH of the water means nothing for mashing. It's the residual alkalinity. Ions, residual alkalinity, hardness and grist all play a part and they all balance (or imbalance) each other differently when one is changed.

It's an intricate foursome, and not the good kind.

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Old 04-22-2009, 08:30 PM   #7
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Harder water has a buffering capacity, therefore if your aim is make your water more acidic, otherwise lowing the pH, it will be more difficult to do so with harder water.

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Old 04-24-2009, 09:50 PM   #8
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There are three main water parameters: pH, Hardness, and Alkalinity.

pH is the measure of hydrogen ions in the water. But that is hard to comprehend in reality, so you can think of it as a scale of acidity.

Hardness is the measure of dissolved mineral ions in the water (primarily Calcium and Magnesium). Hard water has a lot of dissolved minerals. Soft water has few dissolved minerals. Hardness is totally independent of pH. You can have soft water at a high pH, soft water at a low pH, hard water at a high pH, or hard water at a low pH. There is no direct connection between hardness and pH.

Alkalinity is the measure of how well the water can resist a change to become more acidic. In other words, how well can the water resist a drop in pH. Some people will say it is the ability to resist a change in pH, but Alkalinity will specifically resist a drop in pH. The reason it works is that when a solution becomes more acidic it does so through an increase in the number of hydrogen ions. The presence of Alkalinity in the water picks up the free hydrogen atoms so they do not make the solution more acidic, or drop the pH. Alkalinity can also be called carbonate hardness, because it is usually carbonates, or bicarbonates, that provide the Alkalinity (the carbonates are the molecules eating up the free hydrogen ions). However, the more general term for Alkalinity is actually a Buffer. A Buffer will prevent a change in pH, while Alkalinity will prevent a drop in pH. You could also have a buffer that prevents a rise in pH.

In reality Alkalinity and pH should be thought of as separate things. In some cases, depending on what type of buffer you use, increasing the alkalinity will increase the pH. But each buffer will behave differently, and the correlation is not always true. For instance if you use baking soda (sodium bicarbonate) as a buffer, and add it to water, the pH will increase, but will max out at 8.3. So if the pH is 8.3 and you add more baking soda, you are still increasing the Alkalinity, but the pH is not increasing. So in general you should think of them as two separate things.

I would also go to this thread, and read the articles provided by Kaiser. They are more in depth than the info I can provide.

http://www.homebrewtalk.com/f36/bica...rofile-115167/

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Old 04-24-2009, 09:52 PM   #9
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Quote:
Originally Posted by Kata View Post
Harder water has a buffering capacity, therefore if your aim is make your water more acidic, otherwise lowing the pH, it will be more difficult to do so with harder water.
Hard and soft water refer to water hardness. The connection you are referring to is pH and Alkalinity, not Hardness. Alkalinity is a pH buffer not Hardness. Hardness and pH are two independent things.
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Old 04-24-2009, 11:23 PM   #10
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Thank You Boredatwork!

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