pH of water on paper vs meter

We have both a professional (lab) pH meter, and several different version of lab grade pH paper, but are experiencing a very weird phenomenon. We have calibrated all the papers against standards, and they work fine. (And of course our meter is regularly calibrated.) However, when we use the meter to measure the pH of various plain waters (e.g., de-ionized vs. tap) we get consistent readings ranging from 4 to 10 (for different sources), but the pH papers never register anything outside of ~6 for any of these waters. Our tap water, for example, reads 10 on the meter and 6 on the paper. (dry paper reads about 6 -- it's a bit hard to tell whether it's changing at all in the water, because, of course, just wetting it makes it look slightly different, but it's definitely not changing substantially.) Whereas the same paper reads perfectly well in various standards between 2 and 12!) Any idea what might be going on here? Thanks in advance!


