I'll take a swing at this:
I am going to reference Room Temperature, which should be somewhere between 68F and 73F (different ranges in different books), but a consistent target. This is important as you are looking for a reference point for the readings to make sense. If you read at mash temp, then you need to declare what that temperature is - and it changes dramatically batch to batch if you brew a lot of different beer styles.
Fortunately, you only need a small amount of wort to sample, so cooling to a specific temperature is easy in a set of nested steel bowls or a ice water bath and a shaker glass. Literally takes me a few minutes max to take a stable pH reading, even of boiling wort.
1) It varies... much like many of us like to vary mash pH to affect the malt flavors. That said - 5.2-5.0 is the ideal range for break formation. If you believe that an aggressive boil and break precipitation is a mark of good practice, then acidifying the boil can help. The result should be very clear wort into the fermenter. Also keep in mind that boil pH affects hop utilization - so lower pH may have a softer less intense hop utilization, where a higher pH may yield a rougher and more brash hop character. The boil will naturally drop 0.2-0.3 pH units in the boil - so if your mash pH is at a nominal 5.4, then you will naturally see the pH drop into that 5.1 range over time, unless your sparge water is overly alkaline. So experiment on a recipe basis.
2) The cooled sample to room temperature is important. All mash pH and other brewery pH references should be at the same general temperature. It will naturally be lower at boil temperatures... further even than mash pH as the delta is another 60-70F. Room temperature provides a consistent reference point. Better if you can hit specific temps consistently.
3) Post boil pH can be useful to determine yeast activity before krausen shows. The readings should be at room temperature as well. Finish beer pH will, of course, vary by yeast strain. You have seen some of the discussions of final adjustments which can add some more control if you wish to use it.
Acidifying sparge is interesting, as there are two possible goals. The primary should be to remove alkalinity in the water to reduce tannin extraction during lauter. It is also a way of adding acid to the boil as the excess H+ will follow into the boil and have a more immediate effect in the kettle. I have played with acidifying my RO to my mash pH target and had mixed results... so have come back to making a kettle adjustment if I do NOT see good break material after 30 minutes into the boil.
Topic: Boil ph... (Read 5200 times)
