Adler Planetarium

Functional and Fanciful Materials: IMLS Sundial Conservation

In 2012, the Institute of Museum and Library Services (IMLS) awarded the Adler with a two-year Conservation Project Support grant to support conservation treatment of six varieties sundials from the Adler’s historic scientific instruments collection. Sundial artisans chose materials for their beauty, workability or simply based on aesthetic preferences of the time. Considered decorative as well as functional, sundials were carved, engraved or etched with popular motifs, coats of arms, or other iconography. 

Microscope image of compass rose for M-254. The image shows pigment stability and areas where gold leaf was lost.

Microscope image of compass rose for M-254. The image shows pigment stability and areas where gold leaf was lost.

The Adler’s collection contains approximately 450 sundials, showing an amazing diversity of materials. The sundials were fabricated from a large variety of materials, including ivory, wood, gilded metal, brass, bronze, cast iron and various types of stone. While we make great efforts to maintain preventative conservation standards, the materials age over time, and not always gracefully. Wear from historical use, poor repairs, or ‘inherent vice’, a term that refers to incompatibility of composite materials or characteristic instability of materials, can lead to structural damage or loss of parts. 

A crack through ivory diptych sundial, W-136.

A crack through ivory diptych sundial, W-136.

Materials show stress in different ways. Ivory reacts to extremes in relative humidity. Ivory objects also show stains from pollutants, as well as cracks from carving and the addition of materials, such as metal or glass.

Also sensitive to fluctuations in relative humidity, wooden objects also generate some acidity that reacts with metal, causing oxidation or tarnish—a dull, dark appearance of metal’s surface. Wood will shrink and swell depending upon its environment. Over time, this leads to cracks in the object.

Uncoated metal objects develop a surface patina or show signs of oxidation. A patina—the green color on many outdoor bronze or copper sculptures—occurs as a result of contact between metals and moisture over time. 

Garden sundials, intended for outdoor use, were typically constructed of heavier materials, such as limestone, slate or cast iron. Gnomons (shadow casters) and compass parts for garden sundials were made of bronze, brass, or cast iron. If unprotected, these elements frequently show evidence of patinas. In the case of iron, this reaction results in the appearance of rust.

Conservator Tom Fuller (Northwest Objects Conservation) encountered many of these issues when he treated 83 sundials during the Adler’s IMLS project.  Fuller studied each instrument, employing investigative techniques such as microscopy and long and short wave ultra-violet (UV) lights to capture fine details. Medium and long wave UV lamps show the presence of organic coatings or glues. Organic compounds ‘fluoresce’ (their surfaces glow) which indicates the presence of an organic coating, such as shellac. Other materials, such as ivory, bone, or horn have the same appearance under UV light. Such inspections revealed fabrication methods and material composition, which informed his conservation treatment approach. After consultation with curatorial and collections staff, Fuller prescribed and completed the safest treatment.  

Through preventative conservation, the sundials will remain attractive and physically stable for years to come.

Written by Jennifer Brand, collection manager at the Adler Planetarium. 

Conservation project support made possible by IMLS. 


Additional project assistance provided by the North American Sundial Society and Bay & Paul Foundation.

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