Materials in the Magic Kingdom; when it comes to science, Disney doesn't use a Mickey Mouse approach.

For many children and adults alike, a trip to one of Walt Disney's four theme parks is like a pilgrimage to Mecca-it's an excursion they feel they have to make at least once and that they anticipate with excitement and reverence. While there, visitors are immersed in a surreal world where the inhabitants range from human to humanoid and historical characters mingle freely with fictional personalities. Events that would be impossible in real life take place regularly within the parks' boundaries.

In Disney World's Hall of Presidents, for example, Audio-Animatronic figures representing 40 U.S. chief executives, living and dead, convene on one stage to impart words of wisdom to the audience. Abraham Lincoln calls roll, and Bill Clinton delivers a speech. Seeing John F. Kennedy share a stage with George Washington can strike the visitor as fascinating or creepy. Either way, the Disney "Imagineers" have successfully created an illusion. Doing that takes some ingenuity, not just in the mechanisms that imitate facial expressions and gestures, but in the design of materials as well.

At the American Chemical Society meeting in Orlando, Fla., last August, Disney research scientist Kathleen Nelson discussed some of the materials problems facing the theme parks and their approaches to solving them. Nelson is one of a cadre of Disney scientists who dabble in projects ranging from formulating polymers to mimic human skin to making biodegradable casings for fireworks.

Chemistry and materials work takes up less than a tenth of the company's research and development efforts, says Ben Schwegler of Walt Disney Imagineering in Glendale, Calif., but "it's important and highly visible." In other words, it helps put the magic in the Magic Kingdom.

Unlike some other theme parks, Disney has enough special materials needs to justify its own research. The theme parks operated by Busch Entertainment in St. Louis, Mo., leave materials research to the contractors hired to build rides and attractions, says spokesman Fred Jacobs. Busch does do some research focusing on marine life and zoology, however. Universal Studios Florida in Orlando will not discuss any of its technical projects.

Disney keeps most of the research it conducts with universities, companies, and other organizations (SN: 7/29/95, p. 72) under wraps, too. In general, collaborators are forbidden to discuss their affiliation with Mickey Mouse and Co., Schwegler says. Disney worries that organizations claiming an association with the company will undermine its ability to sell movie merchandising tie-ins. "Companies pay us millions of dollars for the right to use the Disney name," explains Schwegler. "We're trying to protect their investment."

Though Disney scientists may develop formulas for polymers and paints, they don't make the actual substances themselves. Instead, specialty manufacturers mix polymers and paint to Disney's specifications.

One of Disney's unique materials problems is the development of skin for the Audio-Animatronic figures. No commercially available polymer has the combination of properties that fits all of Disney's needs, Schwegler says. For a start, the polymer must be durable yet flexible. When Abraham Lincoln gives the same speech dozens of times a day, the repeated bending and stretching can cause tears and cracks in his skin.

Any material, no matter how tough, is bound to fail after many repetitions of a movement. Therefore, the polymer must also be easy to repair. "The real cost isn't the injection or the molding process," Schwegler says. It's in the labor required after the figure has been cast.

The polymer has to have not only the malleability of real skin but also the texture. Artists apply theatrical makeup to the figures as if they were human actors. In addition, head and facial hair is planted directly into the polymer, so it must be dense enough to grip the hair tightly. "We never paint on a beard," Schwegler notes.

Since there are four Disney parks in different parts of the world, Disney scientists must take into account how different climates affect the polymer. "The humidity problems in Florida are different from the desiccation in California," Schwegler says. Freezing winters in Paris and Tokyo add other complications. Large temperature swings can make materials expand and contract, causing them to wear out from fatigue. Each set of conditions requires a slightly different material, Schwegler says.

Though Disney will not reveal the formulation of the polymer, polyurethane or rubber is usually used when scientists want something to look like human skin, says E. Bruce Nauman, a chemical engineer at Rensselaer Polytechnic Institute in Troy, N.Y. Custom-made polyurethanes are easier to make than harder plastics. "They're made by blending two different oligomers, or prepolymers, in different proportions," he explains. "Then you cast them in the shape you want."

For more common industrial applications, companies are usually better off to redesign a plastic part so they can avoid using a custom polymer, Nauman says. "For a given application, it's quite an art to choose which polymer is best."

Disney often can't rely on commercially available products because the special effects designers rarely use materials as the manufacturer intended, Schwegler says. Take paints, for example. "We dilute them and coat them too thick and too thin. We don't use the right type of brushes. We don't use the recommended applications of spray paint." The Disney scientists modify existing paints to fit their particular needs.

Some Disney attractions require especially reliable paint for outdoor use that falls under the category of architectural coatings. Repainting an attraction like Cinderella Castle, even if it's only done every 15 years, means shutting it down, losing revenue, and, ultimately, disappointing visitors, Schwegler says.

The research also involves keeping up with paint formulas that change-in response to new environmental and safety regulations, for example. "Manufacturers change their formulations frequently without saying anything to their customers," Schwegler says. "For people who are able to follow the manufacturer's recommendations, they never see the difference. But because we don't, problems frequently arise."

When most visitors think about safety, they focus on roller coaster rides like Magic Mountain. But Disney also has to pay attention to less obvious dangers. All material at "kid level"-fake leaves, landscaping, even the lava in the Energy Pavilion at Epcot Center-is nontoxic. "You never know what's going to go in a kid's mouth," says Schwegler. The lava isn't very tasty, he says, but it won't make anyone sick. Some of the special effects in the parks are "literally stuff you could make in your kitchen."

Disney's materials scientists also tackle challenges posed by the nightly fireworks displays. In most areas where Disney sets off fireworks, maintenance crews simply go around and pick up the polystyrene shell casings left after the show. They'd prefer to use biodegradable casings, however, in case the debris falls into water or other inaccessible places.

Some types of plastics that are called biodegradable break into smaller pieces without undergoing any fundamental chemical change. "We had many manufacturers come to us, wanting us to test their products," Schwegler says, but these materials don't fit Disney's criteria for biodegradability.

Disney has successfully collaborated with fireworks manufacturers to develop starch-based casings that break down into carbon dioxide, water, and other harmless molecules. The company does not use those casings yet because safety and "business issues" have yet to be resolved, Schwegler says.

The ideal fireworks shell casing would leave no residue at all but would "vaporize like a magician's flash paper in the sky," says polymer chemist Gary Zeller of Zeller International in Downsville, N.Y. Zeller has sent Disney some information on a biodegradable casing he is developing for military applications. The plastic contains enzymes and microbes to speed up its degradation. "The shell turns into mush in 30 days," Zeller says.

Like most companies, Disney is rather tight-lipped about much of its research, but unlike other companies, Disney says, its silence is not just to keep competitors at bay. "When you're at Disney Land, you're on a stage set," Schwegler says. For Disney to reveal its secrets is "like when you go to a magic show and the magician shows you how to do every trick." Thanks to the scientists quietly working behind the scenes, however, all people see is the illusion. n

Letters continued from p. 387 Revisionist art By the time I had finished reading the article on rock painting ("Visions on the Rocks," SN: 10/5/96, p. 216), I was sure I knew how Archimedes felt when he determined how to measure the volume of an irregular object. "Eureka!" I thought, so that's how it happened. For years I had been perplexed by bits of commonality in ancient and prehistoric religions, mythology, and constellations; they were too numerous to be accidental and occurred in cultures separated by vast distances. Altered states of awareness would have produced similar, though not identical, experiences. For example, the central figure in the picture on the cover bears a striking resemblance to the jackal-headed Egyptian god Anubis, complete with capped scepter in his right hand as he conducted the dead to judgment. The researchers may find it advantageous to confer with current scholars of prehistoric religions, mythology, astronomy, and constellations to find meaning in these images. Richard E. Lang Lincoln, Mass.

I have visited and photographed four petroglyph and pictograph sites in the Southwest. However, your statement, "Dots, zig- zags, and other shapes linked to altered states of consciousness appear in all these works," made me examine my notes of a recent meeting at work more carefully. To the left is an excerpt from my notes. Previously, I believed I was just doodling. Now, it's clear that meetings, particularly those after lunch, can induce trances in susceptible individuals. Gilbert C. Jennett Houston, Texas Although I agree that some of the rock art of European prehistory derives from the experience of people in trance states (as anyone who has picked the little mushrooms that cover the meadow in autumn will attest), I do not know how this conclusion was reached by the researcher's documentation of painted images in the Irish passage mounds. No painted images survive on any megalithic structures. You must be referring to rock engravings. Nicholas R. Mann Albuquerque, N.M.

I wonder about the present-day shamans of the San tribe: Did they have anything to say about the paintings? Ellie Gunn McMinnville, Ore.

Arrows of sickness and man-beast shamans? Nah. I'll tell you what's really going on in that cave painting. Some of the images do double duty, but I assume that's because the artist ran out of wall space. What we have here is a stressed-out executive-okay, maybe it is a shaman after too many trips to the spirit world-trying to get some weekend relaxation at the club. At the upper right, we see him set off in his golf cart, waving at someone behind him. But it's not going well at all. At one point (upper left), he smashes one of his clubs against a boulder. The fish symbols tell us he's having a terrible time with water hazards. The main picture shows him retrieving a ball from the pond (probably on the 7th hole, if the number of fish is anything to go by). In its second meaning, the main picture now shows him at the 18th hole, committing a serious breach of the rules by surreptitiously dropping his ball into the cup (he hasn't even removed the flag). But the members of the previous foursome, over there by the clubhouse and pro shop, have seen him and will probably report him to the steward. Finally, we come back to the first image, which now shows him sitting dejectedly in his golf cart, having just thrown his entire bag of clubs into the stream. Let me know if you need any more help. Martin Graetz Acton, Mass.

Explosive reactions Your article on new developments in taggants is interesting, but it contains some flaws ("Tagged Out," SN: 9/14/96, p. 168). For example, you criticize tests showing instability in gunpowder and taggant mixtures because they were conducted at a high temperature. It is common to raise test temperatures to speed a reaction. Also, gunpowder can be subjected to high temperatures when a cartridge is inserted in the chamber of a recently fired firearm. It is important to know if the high chamber temperature will cause a hazardous condition. Also, you tend to equate black powder and gunpowder. Black powder has not been widely used in firearms since the invention of smokeless powder in the late 1800s. Keith Pyle Austin, Texas

Raising the temperature is a common practice to speed a reaction, but the high concentration of the taggants may have caused problems too. The recommended concentration of taggants is 250 parts per million-a far cry from the 50 percent used. Tests-not to mention years of experience-have shown that at low concentrations, tagged powder is safe. Black and smokeless powders are both gunpowders, and both are explicitly named in the antiterrorism act. According to the Bureau of Alcohol, Tobacco, and Firearms, black powder was used in at least 1,643 bombs between 1990 and 1994.

- C. Wu

You describe a method of tagging explosive ingredients by substituting nonstandard isotopes in various concentrations. The isotope combinations can then be used to identify where the chemicals were sold. It seems like this scheme could be thwarted by combining many portions of the chemical (in varying amounts) purchased at different locations. Since there is only a limited number of isotopes of any element, the same isotopes must be reused in different concentrations at the different locations. The resulting mixture will have a weighted average concentration of each isotope, thus "smearing" the isotopic signature. Alan Balkany Ann Arbor, Mich.

Isotag proposes giving each manufacturer its own rare element isotope as an identifier, then using isotope combinations of chemicals that already exist in the explosive to identify the date of manufacture and distributor. This scheme would offer thousands of possible chemical tags, though you could still lose some of the date and distributor information. If a suspect is found to have bought the various powders identified in the bomb, it would add to the likelihood that he or she is culpable. - C. Wu

You say the Swiss have successfully used microtaggants in solving 559 bombing cases since 1984. That's almost one a week! Who or what are the Swiss mad at? Bernard L. Hill Jr. New Orleans, La.

According to the Scientific Research Service in Zurich, there were 565 bombing cases in Switzerland between 1984 and 1994, including 258 attacks and safe breakings. Only about 16.2 percent of incidents involving untagged explosives were solved, compared to 44.4 percent of cases involving tagged explosives, safety fuses, or detonating cords, all required by the Swiss government. - C. Wu