Media pH

[Ben Belton]

How do you test the pH of your media?

Lots of people test it before they add the agar, but agar will decrease your pH. If the media is hot enough to melt the agar, then it is too hot for my pH pen. I would use the strips, but the agar I'm using has charcoal in it and that makes the strips hard to read.

Suggestions?

Thanks,
Ben

[Royal]

Ben,

The media I use is complete with agar. I tried checking it with my "pen" but the heat and agar messed with the probe.

I have since gone to strips when (if) I check pH. I don't even check my standard media anymore. It always reads the same. The strips are tricky but I found some with 5.5 and 6.0 "pads" that are a nice green color that are easy to see through any charcoal grit.

[Ben Belton]

Yeah, I usually get media without agar because it always seems there is too much.

OK, thanks. I'll keep working with it.

[Des]

I just take a sample and let it cool before testing .

[John D.]

I do the same as Des take a small sample and let it cool then use test strips. The media I use are pretty consistant, so after making the same adjustments for several batches I forgo the test and adjust with the same quantity of KOH to give the pH I want.