Flowers Out of Glass

Nancy Marie Brown
September 01, 1999

Many people think that we have some secret apparatus by which we can squeeze glass suddenly into these forms, but it is not so. We have tact. —Leopold Blaschka

Before he began making flowers, Leopold Blaschka sold glass eyes. Beakers and test-tubes. Beads. His models of marine creatures—squid, jellyfish, sea anemones, octopi—sold to museums all over the world. In 1860, he met Prince Camil de Rohan, the French-emigre ruler of a Bohemian principality and a keeper of vast greenhouses, to which Rohan gave the glassmaker entree. Leopold Blaschka, and later his son Rudolph, shared a passion for natural history. The flowers and plants they began making out of glass were not art, in intent, though breathtaking; they were a scientific undertaking: exquisitely accurate, exact in the replication of every last detail.

light orange flower
Hillel Burger, Harvard Botanical Museum

Prince Rohan displayed them in his castle. They were exhibited a year later at the Royal Botanical Garden in Dresden. Soon word of the Blaschkas' new work had crossed the Atlantic to George Lincoln Goodale at Harvard's Botanical Museum. Goodale had seen the squids and octopi. He decided to commission a set of glass flowers to be used as classroom aids, for teaching botany through a New England winter was the height of frustration. Specimens weren't readily to hand, except those pressed between herbarium sheets, the faded remains of glorious summer days spent botanizing. Flowers of glass would make an excellent alternative: "precise," "timeless," and "unparalleled."

In 1886, Goodale's former student, Mary Lee Ware and her mother, Elizabeth Ware, heir to a maritime fortune, agreed to underwrite the consignment, which grew, over a span of 50 years, to include close to 3,000 models—830 species—case upon case of leaf, stem, bud, and blossom, all life-sized and so life-like they must, it would seem, eventually wither, along with examples of the sections and cross-sections a botany student might make of stamen, pistil, and ovary (or fruit), magnified as if by the lab's own microscope.

The Glass Flowers are now among the most popular exhibits at Harvard. TV and radio programs in four countries have featured them, as did a mystery novel in the Homer Kelly series by Jane Langton. Donna Tartt and other writers use the Glass Flowers as a Boston icon. Marianne Moore wrote a poem about them. And avant-garde photographer Christopher Williams turned them into symbols of human rights issues.

Yet, "It took a long time for the faculty here to go from thinking about the Glass Flowers as a teaching collection to thinking about them as art objects," said Susan Rossi-Wilcox. Consequently, they have not been shielded as well as they might have been from the effects of dust and age. Rossi-Wilcox, a curatorial associate at the Botanical Museum, has "a special devotion," as she put it, to the Glass Flowers. She has enlisted Penn State's Carlo Pantano to see what more can be done.

The Ware Collection of Blaschka Glass Models of Plants fills row after row of cases two tiers high, the models unappealingly arranged to maximize the use of space and to keep similar species together. There are orchids and irises, a mountain laurel, roses and water lilies, red maple and cacti, pine trees and pineapples, a scarlet runner bean. Each is a mixed-media composition, the glass painted and enameled, the parts held cunningly with wires and glue. The detail is astounding. A card beside the angelica model reads: This specimen has over 2,500 buds and blossoms. Calculated by W.D.

blue red and black flower
Hillel Burger, Harvard Botanical Museum

Rossi-Wilcox laughed. "These people were obsessive. Not only did the Blaschkas make all 2,500 of those buds and blossoms, you have Walter Deane over here counting them.

"To my mind," she continued, "the texture is the single most remarkable part of their work—and also the hardest part for a conservator. Look at those fine hairs!" It's the stem of a cactus, bristling with hundreds of short glass threads. "I'm not sure we could clean that. But it's what makes these models look real."

The sheer mass of the collection is overwhelming: In their heyday the father-and-son Blaschka team sent Harvard 100 sets of models a year, and Rudolf kept on alone, after his father died, until his own death in 1939.

"Here's the Grand Duchess's fig. I don't know much about the Grand Duchess of Mecklenburg-Strelitz. Why do we have her fig? It was commissioned by us, paid for by us, but for some reason it was her tree.

You can be sure there's an interesting story. It's one of my favorites," Rossi-Wilcox added. "My grandfather had a fig tree—it's very hard to grow figs in Ohio—and I was his assistant. I'd carry his pail, and he would save the first figs for me." She turned down yet another row. "Here's a cashew. That's a plant I still have not seen in fruit, or even in flower. The only time I've seen a 'cashew apple' is here in the museum. Apparently it's delicious.

"I knew the banana as a model, too, before I ever saw it in flower."

There are many fruits and fibers in the collection, Rossi-Wilcox explained, as well as other "useful" plants. "The Botanical Museum's whole mission is 'economic botany.' Cotton, silk, the food we eat . . . We're this odd little sister of taxonomy. The point of making this collection was to make people understand plants that were common in their lives."

Some of the latest—and the best—of the Blaschka models are the series Rudolf made on the diseases of fruit trees. The "rotten fruit" series, Rossi-Wilcox affectionately called them. "They are the most spectacular models he made," she said. "They're animated, realistic. The cut sections don't have the mealiness of real disease, but as fruit, he's got it—all the little weirdnesses of the colors. Anyone who has fruit trees has seen these things.

"But look here: See the white powdery stuff on the leaves? This is glass corrosion. The majority of these models are affected. That's the great irony. The models showing plant diseases are also showing glass diseases.

"Look over here: the strawberries attacked by molds. Rudolf tried to show a pristine model and a diseased model side by side. When I started reading the labels I started getting goosebumps. These—the ones with the white powdery stuff—these were supposed to be the pristine ones. See? The corrosion follows the crack. It looks very suspicious once you've noticed it." Rossi-Wilcox walked back down the rows, and this time she stopped, not before her favorites, but before leaves that were curled and should have been flat. Petals that seemed to have withered. Others that had sprung apart, the layers of glass separating. Glue used to fix earlier cracks had darkened and shrunk and created new gaps. The Glass Flowers needed the attention of a glass doctor, Rossi-Wilcox decided, a glass scientist who "knew about glass and the unique properties glass has. What a weird medium it is for an artist," she added. "There are color problems and compatibility issues, stresses in the material—so many things you don't have to think about if you're working in watercolors."

She began attending the meetings of the Glass Art Society, and at the second conference heard a lecture by Carlo Pantano, director of the Materials Research Institute at Penn State, and a well-known glass scientist. He spoke on "The Surface and Structure of Glass." "His lecture was so successful," Rossi-Wilcox remembered. "He had so many questions afterwards that they just had to break it up, so he invited people to have lunch with him and continue the discussion. We flooded the restaurant. Here he was, this guy in a suit, followed by about 40 artists shouting, 'Professor! Professor!'" She laughed. "But he was willing to explain things in a way that we could understand. He helped us think about it on an atomic level, about the forces interacting inside the glass.

"I didn't have a chance to talk to him then," Rossi-Wilcox continued, "but later I saw him in the art gallery and I told him about our glass corrosion problem. He knew of the Glass Flowers, though he'd never seen them." He agreed to work on the project. As Rossi-Wilcox explained, "He's very approachable, very charming, but there's this insistence about him that when something has to be done, it will be done well."

Students of medieval history learn this explanation for why the glass in a cathedral's stained glass windows is thicker at the bottom: Glass is a liquid; over time, it slowly flows toward the ground and collects at the bottom of the pane.

"Are they still teaching that?" Pantano said incredulously. "I bet you've also heard that if you put a little dot on a pane of glass and come back several years later you'll see the dot has moved. I learned that in elementary school.

"They're both wrong.

"The reason old glass is thicker at the bottom is the way it's made," he continued. "It's what they call 'crown glass.' You blow glass on the end of a long pipe until you have a big bubble, then you burst it and lay it out flat while it's still warm. Just imagine you and me doing that. Rolling it out on a table, trying to keep it warm and roll it flat. It's not going to be perfectly flat. Then you cut it up and give the pieces to the carpenter. If he's logical, he sets it in the window with the thick side on the bottom, it'll stand up while he caulks around it. It's much easier to work with.

"And glass is not a liquid. Once you cool it, it becomes a solid. Absolutely a solid. But it has the structure of a liquid. That's what confuses people. It's a frozen liquid.

"Now usually we use the word freeze to describe what happens when water becomes ice. That's not what I mean," he clarified quickly. "When water becomes ice, you don't preserve the liquid structure. You transform the liquid structure by forming ice crystals. When glass becomes a solid, on the other hand, it doesn't form a slush or a frozen skin like ice does. The whole thing gradually solidifies. So when I say it's frozen, I mean that those atoms that were all jumbled, all moving around in the liquid—they just get stuck in those positions. They're frozen in place.

"Glass is a non-crystalline solid material. Its atoms are randomly arranged. If you drew its structure, using balls for the atoms and sticks for the connections between atoms, you'd see that the sticks are at all different angles and the balls are at all different distances. And you have all different sized balls, because in most glasses you're mixing a lot of different sized atoms together."

Make, for instance, a pure silica glass: "This is not so easy in practice, but relatively straightforward by computer simulation," Pantano wrote in "The Surface and Structure of Glass," a version of his 1994 Glass Art Society lecture. Silica glass, made just out of sand, is a mix of silicon atoms and oxygen atoms, with two oxygens for every silicon. They link together in a network: each silicon atom is chemically bonded to four oxygen atoms; each oxygen atom is bonded to two silicons. There are no "dangling bonds" (except on the surface), no atoms looking for another partner, no sticks without a ball on both ends.

Now make a sodium-silicate glass—traditionally by mixing sand (silica, or silicon dioxide), soda ash (sodium oxide), and limestone (calcium oxide). The presence of sodium and calcium "drastically alters the network structure," Pantano wrote. Rather than being tightly knit, the network now has breaks in it, caused by "non-bridging oxygens"—oxygen atoms that are linked only to one silicon atom, not two. What Pantano called the "modifier atoms," like the calcium and sodium here or, in other glasses, lead or lithium or potassium or magnesium, "are always located in the vicinity of a non-bridging oxygen. These atoms do not form primary bonds in the network, and in general they are only weakly bonded into the structure of the glass." On the computer simulation, it seems these modifier atoms are floating in empty space, surrounded by the rest of the network. "Nevertheless, the network must conform to the size of the modifier atom," Pantano noted; which means that when a large atom is included, such as potassium, the glass network is a rather loose weave.

This structure "directly influences all properties of the glass," Pantano explained. Its viscosity, for instance, or how easily the molten glass pours and flows, depends on the number of non-bridging oxygens. "The pure silica glass," Pantano said, "has an exceedingly high viscosity because every atom must break primary chemical bonds during viscous flow." Glass containing sodium or calcium or some other modifier, on the other hand, flows more easily, since the atoms can move around each other without breaking as many bonds. Each molecule of a modifier—no matter what kind—leaves one break in the network, one non-bridging oxygen, and so reduces the viscosity. But the size of the atoms has another effect. For instance, since a potassium ion is twice the size of a lithium ion, potassium requires more space in the glass structure. "During viscous flow, the relative motion of the network is more difficult near this large ion relative to a small ion such as lithium," Pantano explained. Thus, adding lithium reduces the viscosity of the glass more than adding the same amount of potassium would.

The surface tension of a glass also depends on its chemical composition. "It is this force that acts to spheroidize the glass gather or blown object," Pantano wrote. "It is also the force that rounds the sharp edges of glass during heating and smooths the surface of any glass during flame polishing." It is hard to fuse two different kinds of glasses if their surface tension is not the same.

The tension at a liquid's surface is essentially atoms looking for other atoms to bond with. In a pure silica glass, each silicon atom and its four oxygens make a three-dimensional shape, a tetrahedron. Inside the glass, these tetrahedra can link together, with each oxygen acting as a bridge between two silicons. But what happens at the surface? There has to be an end to the linking, a line of oxygens with one end free, looking for another silicon to bond with and, not finding any, trying to dive back in to the bulk of the glass. To reduce the tension, what can you do? Add boron oxide. "This molecule forms 2-dimensional triangular units in the glass structure," Pantano wrote, "that is, a triangle with a central boron atom and three oxygen atoms at the corners." It lies flat along the surface, giving the dangling oxygens something to bond to.

"Fluorine also has a potent effect in lowering surface tension," Pantano continued. "It, too, concentrates in the surface, but for a different reason than boron-oxide. Fluorine atoms substitute for oxygen atoms at the corners of the silica tetrahedra, but in contrast to oxygen atoms, which demand primary bonds with two other atoms, fluorine seeks only one bond. It is an ideal termination of the network molecular structure at a free surface."

Unfortunately for the unwary glassmaker, it's not only what goes into the melt that makes good glass, but what may come out. Certain chemicals evaporate more easily than others from molten or cooling glass, changing the chemical composition and the properties of the glass surface. Fluorine, for instance, which is so useful for reducing surface tension, is also quite volatile, as are sodium and potassium.

Even after it's been shaped and cooled, glass is subject to chemical changes through weathering and corrosion. Humidity is the most common culprit here. "Initially, it causes the surface to haze or bloom, but in time, a more permanent dimming, pitting, flaking, or crazing of the glass surface may occur," Pantano wrote. "The latter effects cannot be cleaned off; they are irreversible." The process is one of ion exchange: The modifier ions, such as sodium and potassium, are exchanged for hydrogen ions and water molecules at the glass surface. The resulting haze is actually an alkaline film coating the glass surface. "Recall," Pantano wrote, "that glass tends to dissolve in alkaline solution." While the haze can be washed off, it leaves a leached or pitted layer beneath it that further reacts with the water in the air. Eventually, more sodium and potassium ions migrate up from the deeper layers of the glass, leaving holes in the glass network into which water molecules can seep, causing the glass to swell and bonds to break. If nothing is done, Pantano said, the leached layer "can become so thick that it crazes, crizzles, or flakes, or until it becomes a sponge for dirt and soil and renders the glass surface difficult to clean."

There are ways to delay the corrosion. It's mainly lithium, sodium, and potassium and, to a lesser extent, magnesium, calcium, barium, and lead that react with humidity. The more of these elements in the glass, the more weathering and corrosion it will suffer. But add even small amounts of aluminum and boron, and the chemical durability of a glass will be greatly improved. It also helps to have a mix of small ions (lithium or sodium) and large ones (potassium or barium) in a glass. Leaching of the small ions leaves smaller holes for water to seep into, while the occasional large ions will block the formation of channels between non-bridging oxygens, making ion exchange harder.

The Blaschkas knew none of this. Atomic structure, chemical bonding, ion exchange—these are concepts of the late 20th century. "Neither one of these guys was working in the manufacture of glass," Pantano said. "They learned to make glass from chemistry books. They made it in small quantities, and it wasn't very homogeneous. They didn't get the right mix in places."

Rather than being medieval crown glass, or modern "float" glass—made by floating the melt on a river of molten tin in a furnace the length of a football field—the Blaschkas' glass was made by the "updraw process" common in the 1800s. "Imagine a thick sugar syrup," Pantano said. "Put in a bar and slowly lift it up, and you'll pull up a sheet of syrup." Glass made this way is wavy. At first the Blaschkas bought it in quantity from commercial manufacturers, as their records show, but eventually Rudolf began making glass himself—which is part of the problem facing Rossi-Wilcox and Harvard's conservators. "So our first task," Pantano said, "was to figure out how many different glass compositions they had."

In 1993, a Viennese scholar visiting the Blaschkas' gravesite in Dresden ran into Rudolf Blaschka's niece. "She was worried about the graves," said Rossi-Wilcox. "In Dresden, you only rent a grave for ten years, then you have to renew the contract. She was the last relative, and she was afraid no one would renew. So this scholar called me. He said, 'You're Harvard. You have to do something.'" Convinced, Rossi-Wilcox had the contract transferred to Harvard. She also arranged to buy what was left of the Blaschka studio.

"She found hundreds of these little boxes," Pantano said. "Each was filled with a different color glass. It was just like a palette, a painter's palette. There were a lot of yellows and a lot of greens, naturally, and a lot of really gross colors—rejects, or whatever."

Rossi-Wilcox and Pantano collected samples of these cullets to test, along with whatever bits and pieces had already broken off of the models in Harvard's cases. Some of the tests were performed at Harvard, some at Penn State.

"I wanted to analyze their glass year by year," Pantano said, "since we know the years all the plants were made, but there were whole bunches of years for which we couldn't find any broken pieces. There's probably an interesting story there, why some years broke and some didn't."

The simplest answer to why some of the Glass Flowers broke is that they're old, Pantano acknowledged. "And for their first 50 years, they weren't in a controlled environment."

The environment is still not perfect. The air conditioning added in 1980 keeps the humidity down, but the vents suck dust into the cases; the cases themselves are old and not very well sealed: "I really cringe when I see these cases," Rossi-Wilcox said.

But only when they know more about the glasses' chemical composition can Rossi-Wilcox and her colleagues design a better way to display and protect the collection. As she admitted, "This type of art conservation is a new science." But she added, in the profession's defense, that "the Glass Flowers are not like a collection of crystal goblets. We're dealing with both organic and inorganic materials, and the way we need to proceed, from climate control on up, is different."

Pantano examined the glass fragments in cross-section, using a scanning electron microscope to see their structure. Another instrument, called an electron microprobe, allowed him to analyze the chemical composition of each type of glass. "The probe shoots electrons into the sample," he explained, "making x-rays come out of it." These x-rays give the signature of an atom. "If chromium is in the glass, the x-ray will tell me how many atoms of chromium there are."

From the beginning it was clear that the Blaschkas knew how to make colored glass: Add a metal to the melt. Chromium makes bottle green; iron makes brown; cobalt makes blue. "Red is from gold. That's a tough color," Pantano said. "If you look at the Glass Flowers, you won't see a lot of reds. Red's not stable. If you throw gold into the melt, it will start out bright red and then turn mucky. You won't get the color you want." (The Blaschkas learned this by long experience. As Rossi-Wilcox noted, "There's a ten-year set of letters in the archive about the pain of making red glass.") Often, in order to get the shape of a leaf or petal just right or to apply a textured enamel, they would need to reheat the glass several times. "When you put it back in the oven and heat it up again and again, that really stresses a glass," Pantano said. "When you heat the glass, the atoms move apart due to thermal vibrations and structural changes, and the glass expands. If you cool it fast, they do not have time to move back together. Eventually something has to give. It's an internal tug of war—it's that kind of stress that causes glass to break. A crack is just a bunch of broken bonds."

The technique of annealing is used to eliminate this problem, but, says Pantano, "The Blaschkas did not really understand annealing. Annealing is one of the important steps in glass forming. After you melt and shape the glass, you heat it up again—but not so high that it changes shape—and cool it really slowly. That relieves the stress. It lets the atoms relax into new positions." Yet, as Rudolf Blaschka wrote to Mary Lee Ware, If these paper thin blades, as leaves, petals, etc., are burnt in muffles, the objects get shapeless. Instead, he annealed his pieces in an open flame, where the objects can be continually watched, but which may or may not have effectively relaxed their atomic structure. As he wrote to Mary: You would have been surprized to see the half dozen red leaves I had done while you were in Dresden a few days later: smashed, scaling, full of flaws they lay on the table. The process that had given pretty satisfactory results in the small berries . . . failed in the broad blades, a case that often occurs.

The Blaschkas also didn't fully understand the importance of surface tension and thermal expansion mismatch in getting two different glasses to fuse. Pantano reached into his breast pocket and pulled out a plastic petri dish. Carefully wrapped inside was a chipped bit of a leaf. He held it out. "See how it's all clear in the middle? In some models, the Blaschkas made green glass and painted it onto the surface of clear, then heated it until it fused. What I mean by paint is that they took green glass and ground it up—or sometimes they just took chromium oxide powder—and they painted it on the surface of a cool, clear leaf. Then they might take a sharp tool and scratch the coating to make a pattern—of leaf veins, for example. Finally, they put it in the oven and the green glass would melt and fuse into the surface. The mismatch in properties between these two glasses could cause stress, and cracking."

Yet this combination of glasses was the key to the Blaschkas' art. Two pine needles, each a millimeter or so across, show how father and son varied their glass composition to capture the colors of nature. One needle was meant to be fresh, young, newly emerged: Its core is a white opaque glass high in phosphorus; the coating is a clear green glass, colored by chromium and copper, but it has a number of small ribs on it made out of the same white glass as the core. The second needle is a dark green, fully mature pine needle. Its core is a darker, alkali glass rich in magnesium oxide; over that is a lead-oxide enamel containing chromium and copper oxides.

Some leaves Pantano examined contained three or even four different glasses. One, from Podocarpus macrophyllus (the yew pine), had a base glass of transparent green topped by a translucent green glass containing small crystals of chromium oxide. The underside of the leaf was coated with a thin layer of opaque white glass in which there were speckles of tin. The fourth glass was a transparent lime green glass with a high lead content.

"It was a lot of work," said Pantano of the Blaschka's technique. "There are a lot of needles and leaves in that collection."

In 1928, Mary Lee Ware wrote of Rudolf Blaschka, Now he himself makes a large part of the glass and all the enamels, which he powders to use as paint. This he considers to be practically indestructible, except by force—so that, if we could come back in a thousand years, we would find form and color as today.

Yet now, a scant hundred years later, leaves and petals on some of the models are curling, cracking, the surface coating pulling away from its base. "Some of the leaves have so much stress their veins are lifting up," said Rossi-Wilcox. "They're breaking themselves apart. It looks just like they're withering."

Those whose coatings were made with high concentrations of lead and potassium are showing corrosion and weathering—which makes sense, Pantano explained, since lead and potassium "are well-known to limit the chemical durability of glasses in humid environments."

"Was it the Blaschkas' technique?" Rossi-Wilcox asked. "Or the commercial glass they were using? Originally, we thought only large leaves were affected. But then we started looking at smaller leaves, and we realized it came down to a time period, 1888 to 1893."

"It'd be nice if we could come up with a way to do non-destructive testing," Pantano added. "There's a technique called infrared spectroscopy that's good at identifying chemical compounds on surfaces. It can be done by remote sensing, using optical fibers: You put the tip of the fiber to the sample, emit infrared light, then collect the light that comes back off of it. This light goes down the fiber to a spectrograph. It's a new method, but it's already being used in manufacturing facilities where hazardous materials are made and also in the world of 'smart manufacturing.' It's also used for medical purposes." Pantano envisions a portable device that he could take into the Harvard museum and, with a touch of light, diagnose the Glass Flowers' ills.

"But what then? Is there some kind of glue that can keep the core and coating glasses together, a way to cure the cracks? "There are ways to heal cracks in glass with a really sharp laser," Pantano said, "but I think it will be a little too hazardous for the Glass Flowers. It could make it worse. Every crack is different, every glass is different—there's nothing we can practice on."

Instead Pantano is considering trying, as a kind of "glue," a glass-like substance made by what's called the sol/gel process. "It's like making jello," Pantano explained. "It's a random mash of atoms made by dissolving a liquid substance into another liquid." Heat the solution in a beaker. As it cools, it becomes a gel. Eventually it solidifies: "It gets almost as hard as glass." The ingredients are not the same as in real glass, but neither does it take high temperatures to manufacture. And with the right mix of atoms, it can mimic the optical properties of glass. "It's synthetic chemistry. It's really expensive, but if you had a crack, you could take the liquid before it begins to gel and paint it on the crack. Let it become hard, and it will hide the crack. It doesn't pull the crack together, it just fills in the opening. If there's paint on the glass, it won't work—it'll react. But if the leaf is made of all glass, it won't be a problem."

To solve the corrosion problem, Pantano is also investigating the use of a plasma chamber. "It's something like the inside of a neon lamp—something like molecular-scale sand-blasting. You'd put the model in the chamber and zap it. Ions would bombard the surface without mechanical stress, and clean the corrosion products off it. But what if it doesn't come out sparkling?" To get some glass to practice with, Pantano had a high school student working in his lab make samples with the same chemical composition as the Blaschkas' glasses. But even following the recipe as closely as possible, the student's glasses looked better. "The Blaschkas were working with wood stoves and bellows. It's not surprising we didn't get exactly what they got," Pantano noted.

Pantano is currently looking for a student who will continue this work. "I've offered the project to engineering students, but no one has taken me up on it," he said, so he's thinking of recruiting some art majors.

"Materials is a pretty important part of art in general," he noted, sketching out his idea for a collaboration between the Materials Research Institute, which he heads, and Penn State's School of Visual Arts. "But mainly," he admitted, "I'd just like to have a glass-blowing furnace here—a furnace with a big crucible in it, the size of a five- or ten-gallon bucket—almost like a real glass-blowing studio. It would make learning about glass a lot more interesting.

"If you blow your own glass, you feel the heat, you can sense the glass's properties. It's a pretty unique material. It's a liquid when it's hot—you can feel that. Glassblowers say it's 'sweet'—like bubblegum, when you get it just right to make a bubble. "Students could get a real feel for what the substance is all about. And it could be fun."

When George Lincoln Goodale of Harvard's Botanical Museum commissioned the Glass Flowers to be used as teaching aids in 1886, he could just as easily have asked for wax models or plaster ones. "The orthodox view is that wax or plaster models wouldn't carry the detail, but that's not true," said Rossi-Wilcox. "Wax models are every bit as detailed.

"But Goodale knew that glass has this special magic, this attraction, this cachet that no other medium can have.

"It's familiar. We know how fragile it is. Yet it's also sturdy stuff. That's the paradox of the medium.

"And then to see the Glass Flowers—to see how delicate they are—that just blows us away. They look so absolutely real. In terms of detail, nothing was too much trouble for the Blaschkas."

Carlo Pantano, Ph.D., is director of the Materials Research Institute and professor of materials science and engineering in the College of Earth and Mineral Sciences, 198 MRI Bldg., University Park, PA 16802; 814-863-2071; Susan Rossi-Wilcox is curatorial associate at the Harvard Botanical Museum. Pantano's research on the surface and structure of glass has been funded by the National Science Foundation, the Air Force Office of Scientific Research, and the Office of Naval Research.

Last Updated June 23, 2015