# pH pens **URL:** \ **Category:** Factual Questions\ **Created:** [June 24, 2003, 4:24pm UTC](https://boards.straightdope.com/t/ph-pens/184066 "2003-06-24T16:24:37Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![PurplePerson](https://avatars.discourse-cdn.com/v4/letter/p/ec9cab/32.png) [@PurplePerson](https://boards.straightdope.com/u/PurplePerson)\ **Post date:** [June 24, 2003, 4:24pm UTC](https://boards.straightdope.com/t/ph-pens/184066/1 "2003-06-24T16:24:37Z")
Could someone tell me if Ph pens are a reliable source to determine acidity? Thank you. ---
**Author:** ![chukhung](https://avatars.discourse-cdn.com/v4/letter/c/e79b87/32.png) [@chukhung](https://boards.straightdope.com/u/chukhung)\ **Post date:** [June 24, 2003, 6:23pm UTC](https://boards.straightdope.com/t/ph-pens/184066/2 "2003-06-24T18:23:45Z")
Just to avoid confusion, you’re talking about small, electronic pH meters like the ones on this [page](http://www.automatedaquariums.com/h_chkr.htm), right? If so, then, yes, I’ve found them to be accurate and reliable. Just make sure you calibrate regularly and replace the batteries when necessary. I’ve certainly found portable pH meters to be easier to read than the colorimetric methods I’ve used. I used to spend spend minutes looking at a sample and wondering, “Is that closer to the aqua, the blue-green, or maybe the blue?” Now I get an unambiguous number within a few seconds ---
**Author:** ![PurplePerson](https://avatars.discourse-cdn.com/v4/letter/p/ec9cab/32.png) [@PurplePerson](https://boards.straightdope.com/u/PurplePerson)\ **Post date:** [June 24, 2003, 8:37pm UTC](https://boards.straightdope.com/t/ph-pens/184066/3 "2003-06-24T20:37:28Z")
I am actually talking about a pH pen, that looks like a marker, used to test paper for acidic content. However, those big, honkin meters look cool and I bet a piece of paper would respond in an instant. ---
**Author:** ![easy\_e](https://avatars.discourse-cdn.com/v4/letter/e/eb8c5e/32.png) [@easy\_e](https://boards.straightdope.com/u/easy_e)\ **Post date:** [June 24, 2003, 8:47pm UTC](https://boards.straightdope.com/t/ph-pens/184066/4 "2003-06-24T20:47:34Z")
Actually, those meters can only be used to test the pH of a solution. ---
**Author:** ![chukhung](https://avatars.discourse-cdn.com/v4/letter/c/e79b87/32.png) [@chukhung](https://boards.straightdope.com/u/chukhung)\ **Post date:** [June 24, 2003, 9:21pm UTC](https://boards.straightdope.com/t/ph-pens/184066/5 "2003-06-24T21:21:26Z")
> [@](#): > > \*Originally posted by easy e \* > \*\*Actually, those meters can only be used to test the pH of a solution. \*\* To measure the pH of paper, I belive there are “hot-extraction” and “cold-extraction” procedures that can be used to produce solutions that can be measured with a normal, glass-electrode pH meter. After a little Googling, I’ve found standards published by [ASTM](http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/D778.htm?E+mystore) and [ISO](http://www.iso.ch/iso/en/stdsdevelopment/techprog/workprog/TechnicalProgrammeProjectDetailPage.TechnicalProgrammeProjectDetail?csnumber=31412) on how to do this. This page has an annotated bibliography on methods of measuring the pH of paper that may be of interest: [http://palimpsest.stanford.edu/byorg/abbey/ap/ap04/ap04-1/ap04-107.html](http://palimpsest.stanford.edu/byorg/abbey/ap/ap04/ap04-1/ap04-107.html). It looks fairly old, though, so I’m not sure what’s considered “state-of-the-art” these days. ---
**Author:** ![PurplePerson](https://avatars.discourse-cdn.com/v4/letter/p/ec9cab/32.png) [@PurplePerson](https://boards.straightdope.com/u/PurplePerson)\ **Post date:** [June 24, 2003, 10:48pm UTC](https://boards.straightdope.com/t/ph-pens/184066/6 "2003-06-24T22:48:14Z")
Your Googling looks good. I thought I did Googling, but it must have been done differently. I think I just wrote pH pens. I should have explored differently. Who knows what I wrote. :rolleyes: These site look really good. I will explore them this evening. I check marked all of them. Thank you.