Weird Water PH Experience

[Gregory T]

How I got a 3.35 mash PH reading

I brewed a Belgian Blonde yesterday

10 lb German - Extra Pale Premium Pilsner Malt 38 1.5 75.5%
1 lb German - Vienna 37 4 7.5%
0.5 lb Belgian - Biscuit 35 23 3.8%
0.25 lb German - Melanoidin 37 25 1.9%
1 lb Cane Sugar - boil
1 lb flaked barley

9.25 Gallon Full Mash (BIAB)

3 grams calcium chloride
1 gram gypsum
1 gram Epsom salt
1 gram canning salt

Step Mash

20 minutes 113°F
20 minutes 135°F
60 minutes 158°F

Target PH 5.3 (room temperature)

Brewers friend called for 50 ml phosphoric acid 10%
Bru n water called for 30 ml

I added 30 ml

I use a recirculating HERMS system

I doughed in at 113°F

I took a Sample after 10 minutes

Using PH56 meter

It read 3.35 at 72°F

I checked the meter against RO water. It read 7.5. I checked against 7.1 calibration solution, it read 7.05

I calibrated the meter. It still read 3.35

I added 1 teaspoon baking soda and I created temperature to 135°F

Took sample after 10 minutes and cooled to room temperature

It read 5.83

I then added acid and salts to get the PH under 5.6

I got a reading at 5.23

It eventually settled around 5.45

This makes zero sense to me. The only conclusion I can draw is the 3.35 was an erroneous reading. However, the meter performed correctly on other readings. Did I somehow get a bad sample? There is no way 1 tsp baking soda bumped the PH by 2.5

Perhaps because it was during an acid rest the PH was way off?

I have no idea

Any ideas or similar experiences

 

[Vale71]

Two possible explanations:

- the probe of your PH meter is toast, replace if possible otherwise replace meter with new one. Only way to know for sure is with two-point calibration (7 and 4) or check against known working meter.
- you thought you added 10% phosphoric but addedd 80% phosphoric instead.

 

[Silver_Is_Money]

Presuming that a TSP of Baking Soda is about 4.5 grams, it does does not appear that a mere 4.5 grams of baking soda could move a 3.35 pH Wort with your grist and water and minerals up to pH 5.85. Something more along the line of 25 grams of baking soda would likely have been required. Given everything you started with it seems nigh-on impossible that you mashed at pH 3.35.

 

[mabrungard]

Agree, there is virtually no way that the pH measurement was accurate or correct. Go ahead and get a replacement probe since it does not appear that its performing correctly.

 

[Gregory T]

Thanks for the replies. New probe is a good idea. Such a strange outlier of a reading. I was wanting to do a test on PH and color pick up at the boil. That’s out the window now. The good news is, I made beer