Students Compare Flattening Methods for Tracing Paper

This spring, my lab students had a unique opportunity to compare the effectiveness of two treatment methods.  While ours was an informal observation, it was nevertheless informative for future projects!

Our class was conducting conservation treatment on a batch of rolled architectural drawings.  These drawings were on tracing paper, a material that can respond unpredictably to water exposure.  Unfortunately, the most effective way to flatten rolled documents is through humidification!  This poses a challenge for both preservation and access.

After testing our media for water solubility, the first half of the class proceeded with humidification and flattening through one method that is fairly well accepted in paper conservation.  These documents were dried between blotter paper and stiff boards, beneath weights.  The resulting documents were flat for storage and handling, but slightly rippled.  Could we do any better?

The second half of the class responded by using a drying method called the hard-soft sandwich.  This method was developed in response to the special needs of tracing paper, in a publication by Hildegard Homburger and Barbara Korbel (see below).  Differences in this method as compared to a traditional blotter stack include:

  • Felt instead of blotter paper as one layer of the stack.
  • Significantly increased weight on the stack.
  • Increased drying time.

    And it worked!
The hard-soft sandwich, a drying method devised for tracing paper

The resulting sheets had fewer ripples in the surface, making subsequent mending of tears easier.

Though these are informal findings, this class did present a unique opportunity to compare drying methods on similar materials with similar provenance and storage history, all from the same collection.  Managing such parameters on historical materials is a major challenge in conservation research.  Thanks to my lab students for taking on this learning experience with me!


Homburger, Hildegard and Barbara Korbel. “Architectural Drawings on Transparent Paper:
Modifications of Conservation Treatments.” Book and Paper Group Annual 18: 25-33.

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