I don't see much of a problem with the method, but I'll think about it tomorrow (well, today - it's 1 AM here).
Any suggestions for a culinary pH meter?
Currently, I'm using universal indicator paper from lab supply store, but you can do the same with strong tea. Seriously. It gets brighter when you add acids and dark/cloudy when exposed to bases. With some practice, I taught myself to estimate pH with a margin of error close to the one on a universal paper using lye, citric acid and some maths to work out all them ion concentrations. Can get messy, but it's a fun experiment.
Remember to take out the bag, though. ;)