Alkaline Paper Advocate

Volume 1, Number 2
Jul 1994

Understanding the German Paper Standard, DIN 6738

by Helmut Bansa*

The Deutsches Institut für Normung (German Standards Institute) approved a standard named DIN 6738, "Papier und Karton: Lebensdauer-Klassen (Paper and Board: Lifespan Classes)," in April 1992. This is a permanent paper standard with four levels of permanence. It is not easy to understand even in English translation, but it does offer an example of a standard based on accelerated aging. Dr. Bansa has kindly agreed to provide the following explanation for English-speaking readers.

DIN 6738 is based entirely on the effect of accelerated aging on the strength of the paper. This means that it defines permanence in terms of the paper's "performance" rather than the materials of which it is made.

The procedure is as follows: Take a certain amount of a certain paper; check a) the tensile strength in cross direction, b) stretch at break in machine direction and c) tear resistance in machine direction; age it in the oven at 80°C and 65% RH for 6, 12 and 24 days; and perform the same strength tests again after each aging period.

After the 24-day aging period, calculate how much strength has been retained after aging, based not on the paper's actual original strength but on the standard's "minimum requirements": 5N (tensile), 0.5% (stretch at break) and 50mN (tearing resistance). If the paper has lost no more than 15% of the minimum requirement value on any of the three tests, the paper has a lifespan factor of 0.85 (1.00 less 0.15), and is said to fall into "lifespan class (LC) 24-85." Papers in this group may be called permanent.

If a paper does not meet the defined requirements after aging for 24 days, calculate the strength after aging for 12 days as a percentage of the minimum requirement for each strength measure. If the paper has lost no more than 20%, the paper has a lifespan factor of 0.80, and is said to fall into "lifespan class 12-80." Papers in this LC may be expected to have a lifespan of several hundred years. And so on. Other lifespan classes are LC 6-70, which will last at least 100 years, and LC 6-40, which will last at least 50 years.

There have been strong protests against this standard, mainly but not exclusively from libraries and archives. The reason for this protest was definitely not the "performance principle" but the way it is used in DIN 6738. Some research work has been done on this topic, which the Alkaline Paper Advocate will report in a forthcoming issue.

*Dr. Helmut Bansa, Bayerische Staatsbibliothek, Ludwigstrasse 16, 80539 München 34, Germany

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