[erockrph]

Ever since I started brewing All-Grain I was only using calculators (either BrunWater and/or Kai's calculator on Brewer's Friend) to determine my water adjustments and never measured pH. The only beer that has had a water issue was my first porter, which was too acidic. I used a higher mash pH for a rebrew (again - based solely on what the calculators were telling me), and nailed it. Every other beer seems to be doing exactly what I want it to do from a pH standpoint.

I recently picked up some colorpHast strips and started using them a few batches ago to check my mash pH. I'm not trying to diagnose any problems (I don't feel like I have any right now), but I just want a quality control check. I shoot for pH in the 5.3-5.4 range for most of my brews, but I have been getting readings between 4.8-5.1. I know the colorpHast strips read a bit low, but when I'm reading 4.8 on a beer that I'm targeting 5.4 something seems off. All the beers have tasted fine, so I think the issue is in my use of the strips rather than in my actual pH.

I have been waiting until about 20-30 minutes into the mash, then drain about 1/2 an ounce into a Red Solo Cup. I let it sit until it comes to room temp, then dip my strip for 10 seconds or so. My first thought is that I may be getting enough evaporation to concentrate my wort, and therefore decreasing the pH a bit. Any other thoughts or suggestions?

[narcout]

While I don't think there's any harm in it, you don't need to wait 20-30 minutes into the mash.  If you scroll over cell G27 on tab 4 of Brun Water, it actually says the mash pH tends to rise a bit as the duration increases and that the estimate given is for the early stage of mashing.

Also, there is no need to let the sample cool to room temperature.  The stips will give you the same reading regardless of whether you let the sample cool or not (try it and see; I just dip mine directly into the mash).  I'm not sure what the explanation for that is, maybe they cool to room temp on their own pretty quickly after they are dipped.

Colorphast strips to tend to read about 0.3 too low.  Are you reading them in natural light?  I've found that indoor lighting can throw the colors off quite a bit.

I've compared them against a pH meter several times and have always found them to be pretty accurate (to the point where I rarely bother with the meter anymore).

[klickitat jim]

I test mine at ten minutes after a good stir. Then I don't worry about ph after that. Anymore I only test ph if I'm doing something new.

I let my strip soak for one minute like my instructions suggest. For color comparison I go with the next higher number if it looks in between. Personally if I'm in the 5s I'm happy, and I'm usually 5.2-5.4. Occasionally I test plain water to verify my strips are correct. My well is a point or two south of 7.

Then I do a refractometer test at an hour, and again at 90 and every 15 until I hit my points. I only use ny hydrometer once it's in the bucket

[a10t2]

The stips will give you the same reading regardless of whether you let the sample cool or not (try it and see; I just dip mine directly into the mash).

That's interesting. I just checked mine and read 5.0 for the sample direct from the mash and ~5.1 (in between 5.0 and 5.3, at any rate) for the cooled sample. I pulled a small sample (~1 mL) in a syringe and let it cool for a minute or two before taking the reading.

Are you reading them in natural light?  I've found that indoor lighting can throw the colors off quite a bit.

I agree with this 100%. Sunlight or incandescent if sunlight isn't an option.