Ph Observation and Question

[Niatras]

I was at work yesterday measuring the Ph of ink and noticed something that made me think of brewing. I had a bucket of tap water to rinse off Ph meter probe as well cleaning off the Zahn Cup. When I rinsed off the probe, I noticed that the Ph of the dirty water was around 7.5. I didn’t have time to get fresh water. This water had been sitting in that bucket for 24 hours. The day before, the Ph of the fresh water was 9.5. It dropped 2 points in 24 hours.

This made me think about strike water that might sit overnight for timed heating. Would the Ph drop in this water as well and how would that affect salt additions/Acidulated malt? Would all my calculations now be off?

 

[DBhomebrew]

The water pH is not meaningful, only the mash pH. What would be of concern is whether the alkalinity had changed overnight.

 

[Niatras]

That is exactly my concern.

 

[dmtaylor]

Exposure to air will absorb CO2 from the atmosphere into the water. This is especially true if splashing is involved when running your water into the mash tun or other holding tank, i.e., the more air exposure, surface area, time, etc. (several factors), the more CO2 will dissolve into the water, which is acidic as carbonic acid, and thus will cause pH to decrease. I don't think it would affect pH by 9.5 to 7.5 or anything drastic like that, but, have not run tests to know for sure.

 

[Niatras]

I will see this weekend if the water sitting out all night has an affect on my predicted mash Ph.