In art institutions across the globe, time machines and investigation rooms exist behind closed doors. Dusty artworks go in and come out looking centuries younger; artists’ secrets are brought to light; and hidden, unfinished images emerge from behind famous compositions. Every week, we'll peek beneath the microscope and zoom in on the art of preservation, where art meets science and just a little bit of magic: this is Conservation Lab.
Put a few samples of different wood species under the microscope, and you’ll discover woven nets of cells in seemingly endless variations. For conservators, those dazzling patterns are important bits of data. Each distinct feature is a clue that can help identify the species of wood that was used to create a given art object. “In some cases, wood type can be identified by eye,” explains Arlen Heginbotham, a conservator at The Getty in Los Angeles, who specializes in decorative arts and sculpture. “In other cases, you can make a reasonably educated guess, but it is very hard to be sure.”
Oak, beech, and elm are fairly easy to distinguish through observation alone, according to Heginbotham. So are mahogany and walnut, “but there are other less common woods that can be easily mistaken for them,” he points out. “And when it comes to tropical woods, things get extremely complicated. No one knows for sure, but there are probably well over 40,000 species of trees, mostly in tropical environments.”
When confronted with a mysterious species, curators and conservators face the tough decision of whether or not to extract a small sample from the artwork. Identifying the wood can allow conservators to properly replace a missing part, for example, or track wood usage trends during a particular time, or within a single artist’s œuvre. “Sometimes the identity of the wood can have legal implications, too,” remarks the Getty conservator. “For instance, Brazilian Rosewood is protected as an endangered species. Any object in our collection that contains Brazilian Rosewood must have special permission and documentation in order to be able to travel abroad for international exhibitions.”
If knowing the identity of the wood is deemed important enough for research purposes, conservators move forward. “The samples we take are typically small cubes, 2 to 3 mm on a side. They are extracted either with a scalpel or a tiny jeweler’s saw,” Heginbotham tells us. “We freeze the samples in small blocks of ice to hold them in position, then cut them into extremely thin slices using an instrument called a microtome. The thin slices are mounted onto glass slides, and observed through the microscope.”
To analyze the features that appear through the lens, conservators consult online databases such as Inside Wood, or leaf through the International Association of Wood Anatomists’ “List of Microscopic Features for Hardwood Identification.” This 116-page tome speaks at length of vessel arrangement, helical thickenings, prismatic crystals, “fibers with distinctly bordered pits,” and axial parenchyma—to list just a few examples of the insider slang.
Even with such comprehensive glossaries, however, results can be inconclusive. In certain cases, additional tools are brought in to provide better answers: Polarized light can highlight specific types of crystals in the structure, and extremely fine features can be seen through an electron microscope. When that isn't enough, “we often reach out to specialists for advice,” says Heginbotham, “but even specialists can be stumped sometimes.” Such was the case when the Getty tried to identify the lacewood base used by Gauguin for his Head with Horns. Experts concluded it belonged to the Proteaceae family of tropical plants, but still aren't sure of the exact species.
Future technologies may eventually unlock the mystery—though that could take a while, as Heginbotham explains: “There are new methods of identification in development, like DNA and chemical analysis, but these methods are not fully realized yet and are not ‘ready for prime time’ when it comes to analyzing artworks.”
In the meantime, we can keep marveling at the gorgeous photomicrographs obtained through this research. Below are a few examples from the work of Damian Lizun, a fine art conservator with a private practice in Ireland.