I have been touting this pen for years in this community so kudos to him for at least promoting the pH testing.
But he completely misses the boat on acid paper and the video, other than encouraging folks to test their materials, is probably doing more harm than good. In my opinion the video is terrible. Is bad information better than no information?
First, you have to understand what causes acid in paper. It comes from lignin, the cellular component in plant walls which make the cells strong (and allows plants and trees to stand vertically). As lignin breaks down OVER TIME, it creates acids. So paper manufacturers throw in some buffer, typical bicarbonates, into the paper slurry to neutralize the pulp. This is great, it adjusts the pH higher and brings it into the base (or alkaline) side of the scale at the time of manufacture.
But the buffer that has been added at time of manufacturing does not last forever. The lignin in the paper continues to breakdown over time and once the buffer has been used up a tipping point is reached and the acidification process pushes the pH back into the acidic side of the scale. This is a big reason that 'acid-free' paper marketing is meaningless. Who cares if the paper is 'acid free' when you buy it? You want to know that the paper will STAY acid free over time. Doh. I guess it is fine for anyone who is clueless and/or wants to pretend they are making a good decision when buying cheap crap paper.
So you do not simply test your paper once, call it good, and then walk away. You test and continue to test. The video misses the most critical thing about paper and acidification, that it changes over time.
Archival paper has no lignin, they do not use wood pulp, recycled paper, or other sources which contain lignin. This is what makes true archival paper costly. Buying 'acid free' paper at Staples, testing it once as shown in the video, and then thinking that your stamps are fine for the rest of your life is wrong and having a video which implies this is doing more harm than good. If you are going to publish information you ought to at least do simple and preliminary research on the topic you are covering. Don
It is a cheap pen, I consider it a 'consumable'. Plese note that it also has an issue with picking up paper fibers on the tip over time (the tip will actually change color); I assume that this kind of contamination can result in inaccurate markings. So I just frequently replace them. (If anyone has every kept a fish tank, swimming pool, or hot tub they know that you have to constantly check pH over time and that replacing your test kit each year is good practice for accurate reading. How this fellow missed mentioning of any of this critical info in his video is beyond me.)
I test everything including binders and slipcases. Stamps and cover can tone without direct contact, sitting in a cardboard box or a cigar box can great damage stamps with them never touching theses surfaces. Paper breathes, it is constantly trying to normalize with atmospheric conditions it is sitting in. If the surrounding atmosphere has a high RH and the paper moisture content is low, the paper acts like a sponge. Coatings on things can give false readings (in either direction), be sure to test areas like the edges of cardboard if it is coated. Do not be surprised to find that many album slipcases are made of cheap acidic cardboard. Why spend money on costly archival paper and then throw the entire album into an acidic cardboard box? Don
Edit; Keeping a great, STABLE environment goes a long way to forgiving those who cheap out on buying quality paper. Stability in temperature and RH is the key factor, it stops the paper from constantly trying to normalize with atmospheric conditions that are surrounding it. I think that in many situation collectors are aware of environment conditions and this covers up many 'sins'. But the trouble can become acute when the collections move into the hands of family members and materials end up in 'less than ideal' environment (basements, attics, cold back rooms, etc.)
I found what tested positive as more interesting than what did not. He found some sales cards. manila stock pages, glassines, and the "Supersafe" hinges tested as acidic. He did not test Dennison hinges.
Glassines, manila pages, and hinges are staples for many collectors yet most discussion I see is on album paper.
Scott Pages? Minkus Pages? Mystic Heirloom Pages? Palo pages? Lighthouse Stockbooks? Lighthouse Vario-F and G Binders/Slipcases? Vario Pages? For self-produced albums (Steiner), what is the "best" option?
Have the above items been tested?
From the conservation standpoint, what is best practice, for pages and albums? Those are the questions I have, anyway...
I'm going to guess that if common album pages like those sold by Scott were "acid-free" over the long term, meaning a century or more, they would cost too much to be a viable product. I'm sure they're acid-free when they're sold to the consumer, but over time, as Don says, they are going to deteriorate. And that's the real question for most consumer stamp products -- how long will they last in good shape? All I have to go on are the older Scott (and other brands) pages and albums that I come across. Albums that are 50 years old are still in good shape, but those 100 or more years old typically have brittle paper and yellowing which means they are disintegrating. A museum would not use paper that does that, but for 95% of stamp collectors who have not very valuable collections and will be long gone by then, it's probably good enough. What happens to the stamps on those disintegrating pages? I suppose they also become more acidic. Ever worked with some really old stamps and discovered they're as delicate as can be? I've picked up old stamp with tongs and had them crack in two.
Either don't worry about it (because your albums probably aren't going to around in a hundred years) or spend the extra money for truly archival paper. Or wait until someone invents a "DeAcidifier Air Processor" machine you can put into your stamp room next to your dehumidifier. I do use dehumidifiers. And sticky bug traps to foil those paper-eating bugs. We do what we can.
Maybe the most practical approach is to consider a stamp collector's lifespan. After about 50 or so years of collecting, most stamp collections will get sold as part of someone's estate, then divided up and sold in parts. That removes the stamps from the now-old (and increasingly acidic) album pages which undoubtedly saves them from more acidification. Or these collections just get thrown away (gasp!) which solves the whole problem in a different way. The thing is that over a person's collecting years, which I'm estimating at no more than about 50 years or so, most album pages will be okay and therefore the stamps mounted on them will also be fairly okay. Maybe a little more acidic than when brand new, but not noticeably. After that, though, all of it goes into decline.
This is more than likely why most collectors don't worry very much about whether their album pages are acidic. If you don't see any deterioration, you don't worry.
Maybe someone should invent an "acid-meter" like a litmus strip that you put into each album which would measure the increasing acidification of the album pages as the air passes over it as the years go by. Write the date you purchased the pages on it, then check it periodically over the years. It would be like a passive "acid testing pen". Over time that might warn collectors. But I suspect most people don't care enough. Even with our own personal health which disintegrates over time, most people don't do much.
I'm inclined to agree with DrewM. Couple pages (mostly front and back) in my circa 1950 Scott Int'l have some toning, but the rest is in great shape. And I've got a Scott Junior International from 1917 that's clearly printed on nicer paper (cotton?), but that paper shows no yellowing or toning whatsoever, surprisingly - still very fresh.
I suspect, as has been pointed out in this thread and elsewhere, that environmental conditions play a much larger role than how acid-free a given paper is (or isn't).
But this is all mostly anecdotal. Moreover, a real definitive authority on the subject is still lacking; even the philatelic-related matter available (e.g. the studies done by the Collector's Club of Chicago) doesn't go into detail on the role that these other, likely more important factors play beyond 'mere' paper acidity. If there's more out there on this - a published, ideally peer-reviewed journal article would be great - I have yet to come across it.
Given all of the above, and taking into account DrewM's great point about the lifespan of collections, I'm inclined to not really bother with testing paper for acid, etc. And Don's point about keeping surrounding temps/humidity constant as much as possible is great, and one that I never recognized until recently myself.
If something looks toned/foxed/yellowed when acquired, whether stamps, albums, stock cards, etc., get rid of it. (I had some corrugated cardboard inserts in the Scott Int'l I picked up that were there to help keep the page block tight and square, which it did - but over the decades it had toned some of the nearby pages, so the cardboard had to go!) Other than that, and absent more compelling evidence that would cause me to productively worry about acid (or my coming into a much more valuable collection than I currently have), I'm not going to worry too much about it.