Best way to take pH sample in Keggle with False Bottom??

dmcmillen · Mar 2, 2018

I have a single tier, 3 keggle (15.5 gal) system with 2 pumps. My mash tun has a false bottom with .7 gals under the false bottom. I figure my total mash water to include the .7 gals. I heat the mash water to strike temp while recirculating with one of the pumps. When I reach strike temp, I turn off the pump and dough in the grain. At this point I only turn on the pump to recirc if I have to apply heat and turn it off when I'm back at mash temp.

Whenever I take a sample to test pH, I stir rigorously before taking the sample. Here's a recent example of a mash cycle:

Brew: Vanilla Porter, 5 gal batch, water treatments per Bru'n Water 4.2, target pH 5.45, Milwaukee 102 meter, calibrated the day before and tested sample, sample treatment and testing per ajdelange's instructions.

5 min - 5.18 @ 31.1
15 min - 5.08 @ 27.1
25 min - 5.05 @ 25.5
45 min - 5.62 @ 26.1 (note, this sample was taken after applying heat and recircing)
58 min - 5.63 @ 26.7

I guess it would make sense that the pH is lower without the underlet volume, and then the 45 min pH being higher after mixing it in.

I have been hesitant to recirc the mash water (which would mix the underlet volume with the water that the grain is sitting in) because it tends to cool off the mash and it takes some time to get it back to mash temp. Until I started trying to control my pH, this underlet volume has never been a problem, because I just fly sparge till I hit my pre-boil volume so I pretty much always hit my numbers.

I would appreciate some ideas on how I should be handling my pH measurements with my setup. This obviously is not working.

ajdelange · Mar 2, 2018

I'm not sure I'd come to that conclusion. If you added acid to the mash water it is to be expected that the initial couple of pH readings will be low. With an estimated pH of 5.45 a realized pH of 5.63 isn't unreasonable. While you can come closer than that you shouldn't be surprised that you are off this much. A test mash, using the guidance of a spreadsheet or calculator, is really the way to go.

Also, you should calibrate the pH meter just before you brew.

dmcmillen · Mar 2, 2018

Thanks AJ. No acid added, only Gypsum, Calcium Chloride, and Baking Soda. No, I wasn't surprised with the 5.63. Is there any info out there on best practices for a test mash. I'm assuming a test mash would be with about a pound of grain with the appropriate proportions of each grain. I would be concerned with what type of pot to use; don't want to burn the mash if have to apply heat after dough in. Would you do a full 60 min mash? How do you do a test mash?

ajdelange · Mar 2, 2018

When I do one it is usually in a more researchy setting than justified for a brewing session. I fine mill the grains (only 40 grams), dump them into a stainless steel beaker, place that in a temperature regulated water bath and, when I think they are warmed up enough, add the test liquor (DI water to which the appropriate amount of acid has been added and which has been warmed in the same water bath) stir and record pH over time. Someone doing it for checking on a practical mash would follow the same principles but without the fancy equipment e.g. take a pound or so of the grist and add the prepared liquor in the right proportion. The concept of the water bath, implemented as a double boiler, for example, is going to be helpful as keeping the temperature where desired for such a small mass is indeed the tricky part.

If you didn't use liquid acid or sauermalz I am hard pressed to explain a pH reading as low as 5.05. I would want to do the electrode stability test if I saw numbers like that without acid.