The pH of Filofax Paper

Well today I sidetracked a little from my Essay book, to do some pH testing on Filofax paper. I had discussed this briefly with Steve from Philofaxy, and decided to try both the cotton cream paper and white paper. For accurate testing, I sampled five sheets of each and am showing my results below.


Cotton Cream
1: 7.6
2: 8.1
3: 7.9
4: 7.7
5: 8.1
Average: 7.9

White Paper
1: 7.2
2: 7.5
3: 7.2
4: 7.0
5: 7.3
Average: 7.2

So in conclusion, both papers are very close to pH neutral which is encouraging. The Cotton Cream is a little more alkali at 7.9 than the white paper.

Neither of them are verging on the acidic side which is good, and the white paper I have used is from 2003, so it has kept acid free for a substantial amount of time.

All in all – very encouraging!


11 Replies to “The pH of Filofax Paper”

  1. A quick question, the scale you use for this is it a linear scale or logarithmic scale?

    If it’s log you have to be careful taking averages of logs… you have to convert them back to a linear form, take the average and then convert them back to the log scale…


    1. It’s a logarithmic scale, but it should be alright as I am only taking the arithmetic mean for the average and haven’t really looked into the standard deviation, so hopefully there isn’t a need to convert it! I could do – it might be good practice!!

      1. Easy to do with a spreadsheet of course 😉

        All my radio measurements I used to do were in a log scale so I got quite used to putting all the results in to a spreadsheet and converting them back to linear before taking the average.


  2. Hi,

    Could you tell me about the process you used to test for the pH of the paper?


  3. Interestingly I have nearly all my Filofax diaries going back to 1988 and the paper is still reasonably white with very little discolouration. I have used the cotton cream diaries for the last 4 or 5 years but have went back to plain white as I think its archival properties might be better (the paper is also thinner so it doesn’t fill the binder up as much).

    1. That’s good to know, the discolouration is a sign of acidity in the paper, so if there is very little, they should be fairly un-acidic. I did find that the cotton cream ones had a little more acidity in them, but not much – it would be interesting to know how your older cotton cream diaries have lasted.

  4. Recently a friend of mine in the planners business told me that acid-free is an industry standard for paper these days, even in brands/ products that don’t specifically say they are acid-free. He said even the notebooks you buy at the grocery store are most likely acid-free. He doesn’t work for Letts, but he said Letts/ Filofax does use acid-free paper for all their products. I had never heard this before and I was very glad to hear it!

    1. That doesn’t surprise me, so many people want paper to be acid free these days, in some ways it is a bit like ‘hypoallergenic creams’ – a phrase people to come to expect. There are many other qualities that make some papers better than others and last longer, such as their pulp content, but acidity does have an effect on the longevity of paper so acid free is definitely good! I’m not sure all that many reading books use acid free paper yet, but I can’t be sure!

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