Mash ph and strips

[jtp137]

I used Kai's water calculator to get a mash ph of 5.4. Think I needed to add 1.5 tsp of lactic acid. So I got some strips to test the ph I cooled the sample to room temp and the test color was yellow as piss. Color matched up to 4.6 on the strip chart. I started to worry then I checked my tap water and I got the same reading. I know there is no way my tap water is 4.6 or under. I got some lime dissolved it in water and checked color was green showing basic.

So are these strips that inaccurate or did I screw something up? How accurate are these water spreadsheets at predicting ph.

Beer was a belgian dark strong all pils and candy sugar in the boil

 

[muels]

I have no specific experience with the strips but everything I have read says they are inaccurate and unreliable.
Edit to clarify


Sent from my iPad using Home Brew

 

[Natdavis777]

The strips dont really work well. Invest in a decent pH meter if you are wanting to evaluate mash pH accurately.

 

[BowAholic]

I had the exact same experience just last week...the strip was used the check cooled wort after mashout...showed 4.6 as well...no way it's right as calculated pH was 5.8. I ordered a meter that day.

 

[mabrungard]

Paper pH strips are essentially worthless in brewing. The plastic strips are sort of OK, but typically report about 0.3 units too low.

 

[aprichman]

How did you perform the test? pH strips work best when you pipette a small amount of solution (~1 drop) onto the paper itself. In a laboratory setting the strips are really only used for "go or no" tests - in other words if something is extremely acidic or not. For fine measurements a calibrated pH meter is pretty much required unless you want to bust out the burette and perform a titration.

 

[jbuckhead]

I've been having the same experience with the test strips. Mine are from Precision Lab. I even went so far are to do a comparison test acidifying a room temp sample tap water with 88% lactic acid to pH 6.0, confirming with my aquarium titration test kit. In theory the test strips should have turned a shade towards the dark end of the spectrum, but only turned slightly yellow (actually I don't think they changed color at all... Just got wet and appear a different color like wet vs dry paint does). I then took them and my water sample to my LHBS and compared the strips they currently have on he shelf just to make sure I didn't have a bad batch and got the same results with those. I haven't contacted the manufacturer yet. When I do I'll make another post, but I'm not hopeful at this point. Looks like I need to suck it up and buy a pH meter. Are people still getting good results from the $100 Hach meter?

 

[jbuckhead]

So I contacted Precision Laboratories about the test strips and it turns out they were expired. They have about a two year shelf life when stored properly (I was storing them in a hot garage so that probably didn't help much). Since they don't have a date stamp on the bottles (they working on doing that in the future) it's hard to say how old they were when I purchased them a year ago. Judging by the lack of chatter on is subject within this site I'm guessing not too many people are using the strips so they were probably pretty old to begin with. They sent me a couple of fresh vials and they seem to be working just fine. Until I feel like shelling out the cashola for a good pH meter I think I'll try to make these work.