Preserving glass flowers and saving seeds

Conservation in the gallery of glass flowers

Step into the glass flowers exhibit at the Harvard Museum of Natural History, and you’ll be stunned. The 4,300 intricate glass models that represent 780 species—including orchids, pitcher plants, rhododendrons, and banana flowers—are scientifically accurate and astonishingly lifelike. Created in the late 19th and early 20th centuries by the father-and-son glass artists Leopold and Rudolf Blaschka, these models were used to teach botany classes but were also available for the general public to view. When they were introduced, “the public went bananas,” says Scott Fulton, conservator of the exhibit.

Maintaining this one-of-a-kind collection is no easy task. The early models were made of clear glass and held together by wire armature. The Blaschkas then applied a layer of animal glue onto the glass surface before painting the models. Without this glue, the paint would run off, Fulton tells Newscripts. But these adhesives can expand and contract depending on environmental conditions such as humidity, causing the paint to peel off. Also, some pigments fade when exposed to bright light.

Maintaining indoor temperatures at 20–22 °C and relative humidity of 40–45% minimizes the problem. Dim lighting also helps.

For pieces that need repairing, Fulton uses an acrylic adhesive called Paraloid B-72 that’s transparent and shiny, to which he adds pigments to obtain the desired color.

Another challenge to maintenance is the formation of whitish deposits on models that Rudolf Blaschka later developed using colored glass enamel to avoid painting on animal glue. He added lead oxide (PbO) and potassium oxide (K₂O) to the enamel to lower its melting point so he could lay the glass in different layers without causing cracks. But over time, periods of high humidity during the summer months caused PbO and K₂O salts to migrate through the glass and crystallize on the surface. “For the longest time, the public thought it was fake mold made out of glass,” Fulton says. Climate control is key to preventing the phenomenon.

Deterring seed predators

As forests shrink due to human activities, ecologists are trying to restore deforested or degraded tracts of land. Such restoration efforts often involve seeding or planting nursery-grown saplings into the soil. While direct seeding can be cost-effective, it involves a big risk: seed predation.

In oak forests, rodents are especially quick to snag acorns strewn across the forest floor. So, Jorge Castro, an ecologist at the University of Granada, decided to test out a potential—albeit unusual—deterrent: human urine. In the Sierra Nevada National Park in Spain, he scattered Holm oak acorns at 40 locations in 3 plots, then poured 100 mL of urine on top of half the acorns and tap water over the rest. Castro hypothesized that because humans have been chasing and killing rodents such as mice for millennia, a strong odor linked to humans may elicit a fear response in these creatures and drive them away from the seeds.

Previous studies have shown that using urine or other scents from predators such as lynx, bobcats, and minks can repel prey, including mice, thus protecting seeds and seedlings. Sulfur-containing compounds present in the urine, feces, and secretions from the anal gland are largely responsible for proving deterrence and are linked to the predators’ meat-rich diet. So, Castro tested out urine from people who eat meat and from those who consume solely plant-based foods.

To his disappointment, about 98% of the acorns had disappeared by day 7 of the experiment (Restor. Ecol. 2024, DOI: 10.1111/rec.14139). The urine—whether from a vegan or a meat-eater—didn’t repel the acorn thieves. Video recordings showed that it was largely wood mice and occasionally Eurasian jays who removed the acorns. “Mice can be very fast at this,” Castro tells Newscripts. “They ate everything.”

Please send comments and suggestions to newscripts@acs.org.