Mash PH mysteriously high. Lactic Acid Issue?

[Tippsy-Turvy]

Brewed over the weekend and everything seemed fine. As usual, recipe was formulated on Brewer's Friend and water chemistry as per Brunwater. The combination usually produces accurate predictions on the brew metrics.

However, this time the mash ph hit 5.6 instead of the 5.3 I had expected and the sparge 5.8 instead of the 5.4 expected.

I've gone through the software many times and can't find a fault there. I tested my ph meter and the readings were off ~0.1 from the calibration solutions. That leaves either the tap water or lactic acid as the culprit.

Does anyone know how I can test my 90% lactic acid? Eg, if i were to dilute it by a certain amount what ph should I be testing for?

As for the tap water, well there's not much testing I can do myself. I have last year's water report but the mineral content could have changed since then.

 

[Muckdog]

Not sure about testing the acid, but you could use the same for the next batch and stabilize the water beforehand. That would allow you to determine if it's the water or the acid.

 

[AnthonyUK]

As for the tap water, well there's not much testing I can do myself. I have last year's water report but the mineral content could have changed since then.

Exactly. You will need to at least measure alkalinity which you can do with a Salifert kit or other type produced for aquarium uses.
These cost <£10 in UK for 100+ tests (just checked and they are $14 on Amazon).

Getting this right is 90% of the process and is the absolute bare minimum of water testing IMO.

 

[mabrungard]

Anthony nailed it. The most important thing to KNOW about your water supply is its alkalinity, followed closely by the calcium content. Those parameters are the main components in altering mash pH. The aquarium test kits are cheap insurance for those that have shifting water quality.

 

[Tippsy-Turvy]

Thanks guys. Let me look into those aquarium test kits. In the meantime, as an experiment for my next batch i'll try building my water profile from scratch (pure distilled water). Tap water is cheap but it's not worth it if it's going to vary this much.