Finally got my pH overview article good enough for release

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Kaiser

Kaiser

Well-Known Member
Joined
Nov 1, 2005
Messages
3,895
Reaction score
171
Location
Pepperell, MA
I have been working on a few articles about pH for a while. The intent is to provide more insight on the subject of pH from a brewer's point of view. The first article deals with pH basics: what it is, how it is affected and measured. While there are a lot of formulas that could have been presented in that article I intentionally refrained from presenting them b/c that tends to scare people away. And the ones who understand these formulas will be getting their info from other places anyway ;)

The last thing I had to do tonight was to prepare and take pictures of the red cabbage juice pH series. Until I started looking into this pH stuff I didn't even know that the color of red cabbage juice is pH sensitive. It sure made for a neat experiment and pictures but is not very applicable to brewing practice:

An Overview of pH - German Brewing Techniques

I think that the key to understanding pH in brewing is understanding how pH affects the disassociation of weak acids and bases. I hope that I did a good enough job with that.

I always appreciate feedback ;)

Kai
 
Very good article. Brings back memories of making my own cabbage pH test strips as a kid too!
 
Excellent resource. You might also consider adding a section on why brewers should care about pH, i.e. all of the different effects that it has throughout the brewing process, from mashing to fermentation.
 
stoutaholic said:
Excellent resource. You might also consider adding a section on why brewers should care about pH, i.e. all of the different effects that it has throughout the brewing process, from mashing to fermentation.
Click to expand...

It's coming. Don't worry ;). This will be part II.

Kai
 
I know there's more to the series and I'll try not ask questions that weren't in the scope of each part. But there was something I wasn't sure I fully understood.

pH is a measure of the acidity of a solution. It is a measure of the concentration of hydrogen ions (H+; proton). The higher the concentration of hydrogen ions in a solution the more acidc it is and the lower their concentration the more basic it is.
Click to expand...

A substance that donates H+ to or accepts OH- ions from its environment is called an acid. It lowers the pH. A substance that accepts H+ or donates OH- is called a base and it raises the pH.
Click to expand...

So pH is a measurement of H+ ions. Suppose we have a substance accepts or donates OH- ions (implying it does not directly affect the H+ ions)...how does that change the pH? Since pH is a measure of the H+ and not the OH-.

Is it because:
In the case of an OH- acceptor, water molecules disassociate and form more OH- and H+ ions...yielding a resultant increase in H+.
In the case of an OH- donator, the extra OH- joins with some of the existing H+ to form water...yielding a resultant decrease in H+.
???
 
SpanishCastleAle said:
So pH is a measurement of H+ ions. Suppose we have a substance accepts or donates OH- ions (implying it does not directly affect the H+ ions)...how does that change the pH? Since pH is a measure of the H+ and not the OH-.

Is it because:
In the case of an OH- acceptor, water molecules disassociate and form more OH- and H+ ions...yielding a resultant increase in H+.
In the case of an OH- donator, the extra OH- joins with some of the existing H+ to form water...yielding a resultant decrease in H+.
???
Click to expand...

In the Bronstead-Lowry theory of acids and bases, an acid is a proton donator, and a base is a proton accepter. Under this model, strong bases such as NaOH (Sodium Hydroxide or Lye) dissociate into Sodium ions and OH groups. Weaker bases act similarly, but dissociate less fully. Acids do the same thing, but form H+ and some negatively-charged ion. Here "weak" and "strong" are not measures of pH, but measures of how readily the acid or base dissociates.

The "OH acceptor" that you're asking about is a proton. When a H+ and OH- combine, they form water. Pure water has both OH- and H+ present in very small quantities (in any aqueous solution, the concentration of OH times the concentration of H+ = 1x10^-14 As you might expect, the concentrations of each in pure water are equal at 1x10^-7, which leads to the definition of pH=7 as that of pure water).

When something that "donates" OH- ions (which is equivalent to accepting H+ ions) is added to a system in equilibrium, the equilibrium will shift one way or the other due to the H+ + OH- = H2O reaction. This shift is easy to calculate for strong acids and bases, and less easy for weak acids/bases. This goes into the math that Kaiser is purposefully avoiding (people tend to be intimidated by logarithms).
 
dwarven_stout said:
In the Bronstead-Lowry theory of acids and bases, an acid is a proton donator, and a base is a proton accepter. Under this model, strong bases such as NaOH (Sodium Hydroxide or Lye) dissociate into Sodium ions and OH groups. Weaker bases act similarly, but dissociate less fully. Acids do the same thing, but form H+ and some negatively-charged ion. Here "weak" and "strong" are not measures of pH, but measures of how readily the acid or base dissociates.

The "OH acceptor" that you're asking about is a proton. When a H+ and OH- combine, they form water. Pure water has both OH- and H+ present in very small quantities (in any aqueous solution, the concentration of OH times the concentration of H+ = 1x10^-14 As you might expect, the concentrations of each in pure water are equal at 1x10^-7, which leads to the definition of pH=7 as that of pure water).

When something that "donates" OH- ions (which is equivalent to accepting H+ ions) is added to a system in equilibrium, the equilibrium will shift one way or the other due to the H+ + OH- = H2O reaction. This shift is easy to calculate for strong acids and bases, and less easy for weak acids/bases. This goes into the math that Kaiser is purposefully avoiding (people tend to be intimidated by logarithms).
Click to expand...
Thanks dwarven...it's been over 20 years since I took Chemistry or any real math and never really use it (and lol...I work in a Lab!...but not as a Chemist obv). It all fades so fast.;)
 
SpanishCastleAle said:
So pH is a measurement of H+ ions. Suppose we have a substance accepts or donates OH- ions (implying it does not directly affect the H+ ions)...how does that change the pH? Since pH is a measure of the H+ and not the OH-.
Click to expand...

darven_stout aleady answered this, but since this may be necessary for better understanding how the addition of OH- and other bases lower the pH I should add this as well.

Once you look deeper into that subect you will see that all this pH stuff is held together by a number of equilibrium equations that all need to be satisfied. While this is very fascinating I made an effort to stay away from it as not to scare readers away. But that particular principle needs to be mentioned.

Kai
 
Part 2 is now out. It has been on my wiki for a few days while I was tweaking the layout and proof reading it over and over. It seems everytime I read through it my sense of good style and grammar changes and I find new things to change:

http://braukaiser.com/wiki/index.php?title=How_pH_affects_brewing

This part deals with the effects that pH has on brewing processes. I started that before I read Bamforth and Lewis’ Essays in Brewing Science and notices that that article takes the same approach that they took: elaborate on the effects of a particular parameters on many aspects of the brewing process.

Another new thing is icons that I put in the right margin (see the main page for explanation). I hope they help you discern between what is important and what is just nice to know. My intention is to write in a way that provides a lot of information to many brewers and not everybody will understand all the science stuff that I like to elaborate on.

The next part will be the most practical one as it will deal with water chemistry and how its interaction with malt sets the mash pH. I have a lot of data to crunch for that one and it will take me a few more months until that is ready.

Kai
 
Kaiser said:
Part 2 is now out. It has been on my wiki for a few days while I was tweaking the layout and proof reading it over and over. It seems everytime I read through it my sense of good style and grammar changes and I find new things to change:

http://braukaiser.com/wiki/index.php?title=How_pH_affects_brewing

This part deals with the effects that pH has on brewing processes. I started that before I read Bamforth and Lewis’ Essays in Brewing Science and notices that that article takes the same approach that they took: elaborate on the effects of a particular parameters on many aspects of the brewing process.

Another new thing is icons that I put in the right margin (see the main page for explanation). I hope they help you discern between what is important and what is just nice to know. My intention is to write in a way that provides a lot of information to many brewers and not everybody will understand all the science stuff that I like to elaborate on.

The next part will be the most practical one as it will deal with water chemistry and how its interaction with malt sets the mash pH. I have a lot of data to crunch for that one and it will take me a few more months until that is ready.

Kai
Click to expand...

Wow, nice job. I really like the use of graphs and pictures to really illustrate your point. I think you cover everything in the Essays in Brewing and them some.
 
Thanks,

I do like the style of Essays in Brewing Science. But it certainly is not a book for the uneducated brewer. It's more a neat read for brewing geeks. I found Banforth's Tap into the Art of Brewing good as well. It had a lot of "fringe" information that we generally don't find in common home brewing literature.

Kai
 

Similar threads

Silver_Is_Money
A "Standard Candle" by which to confirm Kolbach's mineral pH shift in the mash
Replies
6
Views
907
Silver_Is_Money
Silver_Is_Money
MightyMosin
My yeast notes
Replies
3
Views
2K
MightyMosin
MightyMosin
navethechimp
fermentation (and other) factors that influence final beer pH
Replies
8
Views
3K
navethechimp
navethechimp
HausBrauerei_Harvey
Experienced with water adjustments, but doing my first decoction mash. Help me get the right mash pH
Replies
14
Views
731
HausBrauerei_Harvey
HausBrauerei_Harvey
ChaosB
First Brew Day Results - DIPA on 3v HERMs
Replies
4
Views
1K
ChaosB
ChaosB

Latest posts

Back
Top