Volume 9, Number 1
May 1996

Query

[Once every year or two, a parent calls the office for their young son or daughter, who has chosen the topic of paper permanence for a paper or project, then discovered how few resources are available on the library shelves. Some parents actually write the paper themselves, on the basis of what I was able to tell them in 20 or 30 minutes. I always suggest other sources of information, but they usually say they don't have time to look anything up. I ask to speak to the son or daughter, but this always seems to be impossible or not necessary.

[Recently, however, I received an e-mail message from a subscriber who was taking a much more organized approach to helping her son with a science project. Her message and my reply have been edited and condensed for publication. My reply is an exploration of rough and ready test methods that can be used when lab methods are not appropriate or possible. If any of these methods can be improved upon, readers' comments will be welcome. -Ed.]

To: Abbeypub@aol.com
Subject: Paper tests for a science project
To Ellen McCrady or staff,

I'm a subscriber of both the Abbey Newsletter and the Alkaline Paper Advocate. I am, however, not a book and paper expert. When my 11-year-old son asked me for science project suggestions, I suggested a paper topic to my son. He has chosen, "Which papers last longer and why?"

We have started an accelerated aging test in a dry oven at 194° F. because I saw several articles where folks had done such a test at 90° C. He has chosen 6 different papers (Howard Permalife, Hammermill CopyPlus, Mead 3-hole lined notebook paper, Mead lined writing paper, James River Bond, and newspaper). Three samples of them are on each of two shelves in my oven.

Just some of what I haven't been able to help him with are:

How long in natural aging does so many hours of accelerated aging equate to? I have seen abstracts where some have tested for 72 hours, but some as long as 360 hours. He has planned for a week. And he must do the experiment twice.

How "good" is accelerated aging as an indicator of natural aging? And how even is the temperature in a home oven?

As for tests once the aging is done, we don't know how to perform the fold test (I see where an MIT test is referenced often but can't find procedures).

We have used the Abbey pH testing pen to see how alkaline or acidic the papers are and we have kept a set of the same papers aside as a "control."

Is a comparison of colors appropriate?

Are there any other tests which we could perform on the papers using simple methods? I don't know if a burst test is good for this type of project, but I thought we could maybe take a certain weighted "stone" (or something similar) and drop it from the same height on all of the papers at the end of each test. Sorry to bother you with these questions, but we really need your help! Thanks.

Dear Mrs. Reinhold,

It is not easy to test papers at home, but it is possible to learn something about them and to make some comparisons.

The most frequently used conditions for aging studies today are 90°C/50% RH and 80°C/65% RH. It is important to have some moisture in the air, because the main chemical changes of aging cannot take place without it. I think you need to begin again, with a pan of water in the oven with the samples. This will speed up the deterioration of the paper, and make aging more realistic. Since you don't have any way of knowing exactly what the RH is, just state that you used a pan of water, and report the surface area of the water.

Aging studies typically use an aging period of three days to a month. Under ideal circumstances, you might get away with a three-day test. Ordinary mortals have to plan on a week or more. Because you can't measure as accurately as a chemist could, you have to compensate by inducing big changes that are easy to see. Instead of relying on measured values I suggest using a standard paper to compare all your test papers to.

Another way of compensating for lack of laboratory equipment and methods is to include a standard sample of paper with every batch. Pick a widely available paper, preferably a well-known paper of good quality. You would include one or more of these standard samples in the oven, and put them through the tests with the rest. Then you could say, for instance, "Paper A lasted only half as long as the standard paper in most respects, but Paper B lasted almost as long as the standard paper." (By the way, you should use a fresh piece of each paper for each test, for accuracy.)

Since testing equipment is expensive, use rough equivalents of test measures, like librarians use. The fold test is done by folding a corner of the paper back and forth with your fingers (like a dogear) until it breaks off. Report the results in terms of double folds (back and forth). The primitive burst test the librarians use at the Library of Congress consists of pushing a thumbnail through a piece of paper held in the hand the usual way, with thumb and two or three fingers. Results could be recorded in terms of how easy it was to do. If possible, have several people help with the strength tests (because subjective judgements may be called for, and pooled judgements are more credible than an individual's judgements).

If you are testing the paper for strength after aging, then you have to test it beforehand too, so you will be able to tell how much it has changed. You have to use enough paper of each kind to allow repeating the test several times. In paper labs they may repeat the fold test 15 or 20 times, because paper strength varies widely across each sheet of paper, and there will be a wide spread of readings. For your son's purposes, maybe 3 or 4 times would be OK. The result for each time has to be written down. It would be good to write down the average and the range of variation too. That is, if one person found a certain value most of the time for a certain test, and the other two people found two other values, this should be recorded, in addition to the average for all three.

If the average of fold before aging was 20, and it fell to 3 after aging, you may want to report the percentage decrease in this kind of strength. (Strength can be measured in many ways--edge tear, internal tear, folding endurance, burst, tensile strength, wet and dry zero span tensile strength, and many more.)

What they do in regular lab reports is to graph the decrease in strength for each test they use, as time goes along. This is fun to do, and rewarding to read. They get intermediate values by taking out a piece of each kind of paper at intervals, and testing it. But this might complicate it too much for your son, who is still kind of young.

The Abbey pH Pen does not tell you how acidic or alkaline a paper is, only whether it is above or below a certain narrow range (6.0 to 6.7 or so). Papers can be anywhere from pH 4.0 to 10.0 or above. If you had time, you could order litmus papers and indicator solutions that would tell you the approximate pH of papers above 6.7 and below 6.0.

Testing for resistance to light-aging is easy. You just put your samples in a sunny window, with one half of each sample covered, and see how long it takes for the exposed parts to darken. You can rank-order them by how much they have darkened.

You wanted to know how many years of natural aging are equivalent to a day of oven aging. That all depends on a number of things, including how hot the oven is. Most paper chemists do not like to give more than an approximate figure. In general, I think any paper that comes through a month in the aging oven in good shape has a chance of lasting for 300 years or more.