Conservation Treatment: McDonald Observatory Drawing

This semester, I was pleased to conduct conservation treatment on an architectural drawing of the McDonald Observatory, a leading center for astronomical research and teaching located in the Davis Mountains of West Texas. This 25″ x 42″ charcoal and graphite drawing, made by University of Texas architects in 1934, is housed at the Alexander Architectural Archives here at the University of Texas.

The drawing had several condition issues when it entered the lab. A large tear extended up the center of the drawing, nearly separating the paper in two. The tear had been previously repaired with pressure-sensitive tape, which had become browned and embrittled over time. The tape repair was visible through the drawing’s thin tracing paper. The tear was misaligned along the tape repair, causing gaps in the image and text, as well as rippling from stress in the paper. Creases and grime had resulted from handling. The charcoal had offset during direct contact with storage materials.

Tape removal
Removing discolored tape
Mending the tear on the light table to ensure proper alignment

During treatment, the drawing underwent surface cleaning and several rounds of humidification and flattening to reduce grime and creasing. The discolored tape was removed manually, with controlled application of moisture to soften areas of stiff adhesive. The tear was realigned and mended with heat-set tissue to minimize water exposure to the moisture-sensitive tracing paper. Wheat starch paste was added in small mended areas to improve strength.

Last, a sink mat was constructed to safely house the drawing. The deep walls of the mat hold its cover sheet away from the drawing to prevent further media offset. Acid-free corrugated board was used for structural elements to provide stiffness with minimal weight. A second ply of board, applied cross-grained, was added to support this oversize drawing.

Many thanks to the Alexander Architectural Archives for the chance to work on this beautiful drawing!