What was my pH?

[CadiBrewer]

I brewed an Ordinary Bitter. I was shooting for 5.4 for the pH. My tested readings over the course of the 60 minute mash were:

5min - 5.43
15min - 5.41
30min - 5.37
45min - 5.36
60min - 5.28

All of that was within specs and I'm happy that I came that close to my expected pH, but when targeting a pH, what timeframe during the mash should I hit my targeted pH?

 

[dmtaylor]

Most people recommend measuring about 10 or 15 minutes in. So the somewhat "official" pH was 5.4 indeed.

 

[ajdelange]

I was shooting for 5.4 for the pH. My tested readings over the course of the 60 minute mash were:

5min - 5.43
15min - 5.41
30min - 5.37
45min - 5.36
60min - 5.28

All of that was within specs and I'm happy that I came that close to my expected pH, but when targeting a pH, what timeframe during the mash should I hit my targeted pH?

I recommend taking several readings starting as soon as you can. Generally mash pH is pretty much settled at 20 minutes in but may continue to creep for another 10 minutes. The reason for taking several readings is that with experience you can tell where it is going to level before it does so that you will have a pretty good idea where it is going to go by about 15 minutes. The data when plotted should look something like the blue curve in the graph. In most cases pH is going to creep up a bit over time especially if you have added acid to the mash. If you have added base it will creep down. In the case of Bitter you would have added acid and so your data should follow the blue curve.

The circles represent your data and there are two problems with them. The trend is to lower pH and it is linear; there is no assymptotic behaviour. This strongly suggests that the electrode is drifting. You should run the stability check on the electrode as described in https://www.homebrewtalk.com/forum/threads/ph-meter-calibration.302256/

While, of course, we can't be 100% sure what is happening here the case for electrode drift looks pretty strong. Assuming that it is responsible and assuming that you calibrated the meter just before the first reading the first reading is probably not too far off. Given the typical upward movement of pH over time I would guess that your mash pH ended up close to 5.5 but I wouldn't take that to the bank.