but my question is once you mash in people are saying you are getting conversion with 20 minutes so how can you control or make changes to your mash for this to help with your P.H levels ? 1 you have pull your sample let it cool down ,test it by then you might be 30 minutes into mash and then2 it's too late to add anything to your mash ? is there some way to explain this whole process to for me ?
Here is what I do and have never had mash pH outside of 5.25 - 5.5:
1. Use water from a vending machine with RO, check the water for TDS. I found a machine that is consistently 10 PPM or less TDS, so I figure close enough to zero for everything.
2. Use Bru'n Water to make water chemistry adjustments that would theoretically get me around 5.3 - 5.4 room temp mash pH. Calculate volume of phosphoric acid if required, and prepare volume in a 5 or 10 mL oral syringe.
3. Right after the mash and mineral additions are well mixed, pull a sample in a small container (shot glass or whiskey glass works), and submerge most of the container in an ice bath, stirring until room temperature is met (only takes a couple minutes).
4. Take pH reading to confirm I am within range. I have never been out of range, but I would either add acid or chalk/baking soda depending on what side of the range I am on.
5. Thank Bru'n Water for getting me where I need to be and continue my brew session in confidence.
The time between mashing in and pH reading need not be more than a few minutes.
EDIT: As below, if your mash in and mixing are fairly quick, it is best to let the mash sit for a bit so pH can stabilize. I usually mash in to hit a couple degrees above my target mash and stir vigorously to get it down (I like to overshoot and bring down then have to add more hot water), so once I am done mixing its been several minutes and I figure the pH is stable.