Conservation Treatment: A Drawing by Sir Aston Webb

This spring, I conducted conservation treatment on an architectural drawing from the Alexander Architectural Archives.  The drawing, by British architect Sir Aston Webb, shows a late-19th-century renovation of the Church of St. Bartholomew the Great.  At over 900 years old, St. Bart’s is the oldest surviving church in London!

The drawing presented several condition issues.  It was covered in a significant layer of grime, likely the result of storage in a sooty London office.  The margins displayed a thick layer of brittle, cracked, brown adhesive, likely left behind by a previous display mat.  Most significantly, the drawing had been executed on drawing board, a commercially-produced material that becomes acidic with age.  Given the board’s deterioration, cracks and losses had occurred, and were likely to worsen with handling.  The goals of treatment were to improve stability, access, and aesthetics, and to reduce likelihood of future damage.

First, the drawing was first surface cleaned with brushes and soot sponges, resulting in a notable change in contrast and legibility.  Surface cleaning removed acidic components from paper’s surface to slow future pH shifts and to prepare for water-based treatment.

Raking light reveals the extent of grime removed during surface cleaning

Next, the residual adhesive was softened with successive applications of a methyl cellulose poultice, and mechanically removed with a microspatula.  Methyl cellulose is frequently used in conservation as a controlled moisture delivery method.  The residual adhesive is glue made from animal hide, so it responds to water without need for more aggresive solvents.

Removing adhesive with methyl cellulose

Then, the drawing was removed from its acidic backing board.  This process involved using a modified bone tool to split the drawing from its board. Remaining fibers were then pared away with a modified lifting knife while working on a light table.  This process represents a major change for the item that requires justification.  In this case, removing the backing significantly reduces the risk of future damage, and no significant content was on the back of the drawing.

Portions of the backing board have been split from the drawing

Last, the drawing was washed on damp blotter to reduce acidity, remove degradation components, and reduce discoloration.  A lining of Japanese tissue was then adhered with reversible wheat starch paste to provide ongoing flexibility and stability.

A Japanese tissue lining is adhered with wheat starch paste and a tamping brush

Thanks to the Alexander Architectural Archives for the opportunity to work on this drawing.  I hope to visit this building in London someday!

Before treatment
After treatment

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.