Archive for the 'Spring 2010' Category

« Previous Entries

Meet Eliza, the Flashiest Phone Bot Around!

Eliza sits at her desk in her office. She completes ordinary office tasks—she checks her email, she drinks her coffee, she gets up to go photocopy something or talk to a colleague, and once in a while she checks out the New York Times. Little does she know, she’s being livestreamed to the whole world over the web. If someone calls, she picks up. Sometimes she recognizes the caller, sometimes she does not, and sometimes the connection is so bad that she hangs up and calls back.

Eliza lives on a screen in an eddy of a high-trafficked area, say an out-of-the-way elevator lobby in a busy building. A user sees her and after a couple of minutes, his curiosity gets the best of him and he succumbs to the flashing invitation and calls. To his surprise, after a couple of rings Eliza picks up. Phone conversations are ritualized in the first place and the added awkwardness of voyeurism and conversing with a stranger create the ideal situation for Eliza’s black-belt phone jujitsu which with minimal effort wrests control of the conversation from her interlocutor. It’s a bit like a good dancer foxtrotting and waltzing an overwhelmed novice around the floor.

The prototype is rough, but it works, though because of Flash’s arcane and draconian cross-domain security measures, I can only run it locally through the Flash IDE or stream from my machine using a personal broadcasting service like ustream or livestream (in order for it to work properly on the web, I’d have to host all the components I enumerate below on a single box, something I have neither the hardware nor the inclination to do). The main problem is that I’m making XML socket connections from Flash; if I used a PHP intermediary, I could probably get it working, but again, the whole inclination thing is missing and the thing is already mindbogglingly complicated. Maybe at some point in the future. The following video demonstration will have to do in the meantime.


Warning: this is not for the faint of heart.

Eliza has a ton of moving parts:

  1. The Asterisk script: A simple program that answers phone calls and hands them to a PHP script, which connects via socket to the main SWF.
  2. Various PHP scripts: One to handle connections from Asterisk, one to reset connections from Asterisk after a call ends, and one to initiate callbacks when required.
  3. A simple Java socket server: Adapted from Dan Shiffman’s example, this program runs in the background on the Asterisk server, waiting for connections (phone calls). When a call comes in, it connects it and broadcasts call events (new call, hangup, button press, etc) to the PHP scripts and the main SWF and allows them to talk to each other.
  4. The main SWF: This is the brains of the operation. It loads the movies of Eliza and controls the logic of their looping as well as the logic of the audio (via socket connection back to PHP and then to Asterisk via AGI).
  5. The looping movie files (not completely smooth in this prototype, notice the moving phone and the changing light conditions!): These live in the same directory as the main SWF, which streams them as needed (for a web deployment, they’d probably have to be pre-loaded and played back).
  6. The sound files: These live on the Asterisk box (completely separate from the movies) and are played back over the phone, not the web.

UPDATE: I’m presenting Eliza at Astricon in DC in October, so I should have some interesting observations to report soon. There are several things I’d really like to do. First, I’d like to actually get this working somewhere where I can observe lots of unsuspecting folks interacting with Eliza. I never really got to see someone who didn’t know the backstory calling in, partly because I was exhausted from thesis when I had the chance to show it and partly because there were lingering bugs I had not yet located that occasionally caused the whole thing to stop working—there are so many things on so many separate machines that can go wrong, it took quite a while to troubleshoot. A larger sample of reactions would allow me to rework the conversations so that they’re more disorientingly convincing—better pause timing, more realistically intoned, and taking into account repeat callers’ stratagem’s to see if Eliza is real. I could then reshoot the video so it is completely seamless. That would require monitors, good lighting, laser levels, an OCD continuity editor, and several days of shooting.

If you know of an easy way to overcome the cross-domain headaches, leave me a comment! If you want to fund such an undertaking, please do get in touch! Otherwise, enjoy the video above.

Value Propositions


Update: Pay With A Tweet is a much less silly form of alternative value capture.

My thesis is done! Play with some paywalls.
Watch the presentation.
Hear about it on On the Media on NPR (right at the end, minute 17).

As the world Turings…

For two years I’ve flirtatiously circled the Pygmalion myth, toying with human-machine interactions in which it’s not necessarily clear to the human that s/he’s interacting with a machine or human-human interactions in which both participants are convinced that the other is a machine. I can’t seem to get away from this idea of tricking people into adopting mistaken mental models of interactions. I thought it would be fun to create two bots that would follow each other on Twitter. Caleb Larsen, whom I’ve written about before and with whom I’m beginning to believe I share an eerie and otherworldly mental connection (I found this today, compare to my Obama piece) created a script that updated his Facebook and tweeted randomly generated status messages as part of Whose Life is it Anyway, though in the end he abandoned algorithmically generated messages for appropriation of other people’s statuses—which I find conceptually stronger but no longer relevant to the topic at hand.

In any case, in 1950, Alan Turing wrote a paper about thinking machines. In it he proposed a thought experiment in which a person is asked to converse via teletype with a person and computer pretending to be a person. If s/he is unable to definitively distinguish between the two, goes his argument, the computer is effectively intelligent. People have taken issue with Turing’s conception of intelligence, but nonetheless, over the years, this “Turing test” has spawned doctoral dissertations, colloquia, academic prizes, late-night geek-outs, and many software implementations of computerized interlocutors or “chatterbots.” The first of note was Joseph Weizenbaum’s ELIZA, a Rogerian psychotherapist (you can still talk to her here). She was followed by PARRY, a paranoid schizophrenic. A match made in heaven, I know, but their conversations weren’t nearly as interesting as this exchange between more sophisticated later chatterbots (in this case ALICE and Jabberwacky). Awesome.

There have been a couple of really good ITP projects that riff on what I might call the nebulous interlocutor. Generative Social Networking is my absolute favorite ITP project—in conception, in execution, even in documentation. After using a Bluetooth exploit to download all the contacts on your cellphone, a program calls each number in succession, playing a recording of the last person it called as the other half of the conversation. The most amazing thing when you listen to the demo is the realization that most people have no idea they’re talking to a recording! And some of the “conversations” that develop would easily fool a casual observer too. The ritualized form of phone conversation combined with the latencies and poor connections to which frequent cell phone use have accustomed us make it really hard to tell the difference.

That was part of what made the Popularity Dialer so much fun (and ultimately led to its demise—though creators JennyLC and Cory referred to it last week as “dormant” rather than dead). The premise popular people get lots of phone calls, so what better way to enhance your popularity than by increasing the number of calls you receive? Enter your phone number on a website and schedule a call from one of five characters who think you’re awesome (girl dying to date you being my favorite). At the appointed time, your phone rings and the voice you’ve selected speaks its half of a recorded phone conversation, pausing several beats for you to respond. It seems totally real to onlookers. The problem? It seems totally real to many of the people receiving the calls after their friends entered their number as a prank. Worked great until a humorless FCC lawyer got a call late one night from dude wanting to get some beers.

I love both of these projects. They raise questions about the subjective nature of interaction that don’t get discussed all that much in the literature. So much of an interaction is in our heads. That’s the great lesson of Apple’s marketing—you can take a shitty phone that’s uncomfortable to hold and inconvenient to talk on, but if people are emotionally attached to it, they’ll find using it a pleasure anyway (I think Donald Norman might have said something similar a little more eloquently). In our case, if I think I’m talking to a real person, my experience of that conversation will be radically different from my experience of the exact same conversation if I know I’m talking to a recording—just think of that weird, disjointed feeling you get when a friend’s answering machine picks up and you think it’s him and start talking only to realize a second later that it’s a recording. Richard Powers’s Galatea 2.2 deals with this notion of artificial intelligence as deception, and I want to as well.

I propose a film of a woman with her back to the viewer. She is obviously concentrating hard, occasionally tapping a pencil or reaching for her coffee mug but otherwise moving very little. A phone number is displayed beneath the frame. The viewer calls the number and suddenly the phone on the desk next to the woman rings. She picks it up, and the viewer is amazed to hear her voice both on the screen and through his phone. He speaks to her. She responds that the connection is not clear, she can’t hear him well. He tries to gauge whether she is a real video or a clever program. She hangs up in anger and frustration. She looks at her phone and decides to call back. The viewer’s phone rings and when he picks up, she apologizes for the poor connection and asks him a question. When he answers, she asks another. Suddenly, she has to go. She apologizes, turns toward the screen, waves, and hangs up. The viewer scratches his head and calls back. Her phone rings, she looks at the number and sends the caller directly to voicemail with an over-the-shoulder wag of the finger. And scene!

I’ve seen a couple implementations of phone-enabled interactive movies, but they’re infantile choose-your-own-adventure narratives constructed like corporate phone trees (“if you’d like to see the hero die, please press pound now, otherwise, stay on the line for more options”). I want the interaction to be the purpose of the piece, not a means of advancing a canned story, though I do love the bizarro preview man voiceover in this German interactive “horrah” film:

My system works in a similar way, though without all the voice recognition. I’m interested in exploring how much of such an interaction is actually reactive. In Japan, for instance, it’s definitely over 50%, but I’m working on the assumption that it will be similar for the viewer speaking on the phone, that the character in my movie won’t need to respond directly to the viewer’s words because the social inertia that carries people through uncomfortable party conversations with socially maladroit companions will cause him to behave a certain way in this particular interaction—enough that I’ll be able to maintain some doubt as to whether they’re actually participating in a real conversation. Based on several recent interactions with customer service representatives over the phone, I can’t swear that health insurance companies haven’t already commercialized and adopted this system.


Plentiful bandwidth, virtually free storage, and internet connected cameras has translated into a glut of online video. When anyone can upload to the online panopticon, it’s only a matter of time before people start exploiting the web’s massive audience to crowdsource moonwalks, personal interpretations of the Mos Eisley Cantina scene, ads, or homemade porn—for fun and for profit.

Well, guess what? I don’t want to see your videos. Not the ones you’ve uploaded at least.

The proliferation of cameras everywhere makes it less and less likely that you are ever not being recorded and uploaded the minute you do something remotely interesting. See, for instance, Hong Kong Bus Uncle, the infamous “don’t tase me, bro” (which I find so distasteful that I refuse to link to it), Chinese Airport Woman, and el niñato de Valencia. But again, these are actions performed in public—the operating assumption has to be that someone is recording. And with sites that make live broadcasting as easy as hitting a button on your phone (UStream for instance) popping up like nefarious little mushrooms, it’s entirely possible that your public meltdown will be captured and transmitted live and from several different angles. Totally unscripted reality TV, it’s like your real life, only more interesting.

But not to me. I’m more interested, at least for the purposes of this argument, in recording deviously, either in secret or with unacknowledged intentions. At some point in the future, it’s conceivable to imagine that there will be no place where one is legally protected from being filmed and/or photographed. Or when there are just so many people and devices filming and uploading so many things that prosecuting them all will be impossible, which is functionally equivalent. It is from said future that the ideas that follow come.

What if I created an iPhone app that requires you to hold the device up to your ear as if you were talking on the phone (or when you’re actually talking on a phone with an open source platform) entirely as a pretense to upload video the camera on the back of the phone is recording without your knowledge. There would probably be a lot of hands in the way, but that would make it easier to filter through the results in software. You’d never be in the video so it would be hard to definitively identify it as yours.

A slightly more elaborate variation on that theme would be to build cameras into other devices. One of the big payoffs for me of the Eternal Moonwalk mentioned above is that the majority of people tend to moonwalk across their living rooms, so you get to see the insides of people’s homes all over the world. What if everyone who bought a Roomba were unwittingly inviting an autonomous, wireless streaming surveillance camera into their home? The easiest way I can think of doing this is embedding cameras into particularly nice pieces of furniture left out on New York City sidewalks.

Page scraping and iframes offer another interesting alternative video source which might actually be much less illegal since technically you’re not moving the video from its original location. Instead, you’re finding video content, preferably unembeddable proprietary stuff, and using a web script to strip away any surrounding material and reproduce it in a different place—and it never moves from its original location.

My favorite approach, though, is simply to lie about your intentions. It might be as simple as creating a video high score board for an online game, where instead of their initials, people leave a ten-second taunt for the players they’ve just displaced. A database filled with video taunts has many potential uses. It might be more complicated, for instance creating an online application that uses face detection to perform some non-camera-related function—shaking your head to pan an image back and forth for instance—so that when the application requests access to the user’s web camera, he thinks nothing of pressing “OK,” never suspecting that his face is being displayed on a billboard somewhere across the globe with the supertitle “Did you know that 1 in 3 people has genital herpes?”

Or, as I discovered in the process of writing this post, offer some sort of online video conversion. Video formats are confusing as hell. Put up an all-in-one converter, make it look slick, and simply “keep a backup copy” of people’s video when people upload it!

The Sound of White Space or Pregnant Pause Parturition

As anyone who’s tried to write fiction knows, the real hurdle is not deciding what to write, it’s deciding what not to write. The empty page, like the empty score or the empty canvas, is white not because there is nothing on it but because everything’s on it—possibility, like light, is additive. The act of putting a word on a page, a note in the air, a drop of paint on the canvas removes a bit of that possibility, revealing a glimpse of what it may actually become. I know I’ve read somewhere that a block of uncarved stone contains every sculpture and that it’s only by chipping and chiseling that an artist collapses the artistic wave function into a singular reality. The result is the interface between the remaining possibility (positive space) and the absence of what has been removed (negative space).

Sometimes, though, that interface is deceptive. Foams, for instance, have voluminous contours, but pressure or heat or vigorous movement reveal their deception, reducing them to a mere puddle. Impermeability between negative and positive spaces in a work of art may well correlate to its quality and perdurance, I put that out there to the turtlenecked Barthes and Foucault-reading crowd to discuss. In any case, designers who find commercial success of the Architectural Digest sort are great fans of drawing rigid lines of Germanic severity to divide what’s there from what’s not.

While I find this hard-edged contrast alienating in architectural spaces (I much prefer the worn edges and threadbare plush of vernacular utilitarianism), I all but require it linguistically. There is no place for diaphanous prose in my bookshelf, nor will I fight you for tickets to any recent mainstream movie. Blurring the boundary between meaning and nonsense purposefully is either comedy or chicanery; accidentally, it’s the sign of mental rot.

I find political discourse in general and American political discourse in particular a perfect example of this foamy, insubstantial nonsense, a populist pastiche of pre-chewed jingoistic pablum that fills heads with bubbles that quickly deliquesce to nothing. I was curious, in exploring notions of positive and negative space, to discover how this discourse is actually constructed.

To this end, I took this year’s State of the Union address, all 69 minutes of it, and reduced it to its negative space, cutting out all of President Obama’s utterances. What remains is a strangely compelling silent dance between the beats. How we don’t speak is as idiosyncratic as how we do. In Obama’s case, the space around his words is punctuated with generous pauses and a constantly turning head (though one suspects this may have more to do with the dual teleprompters than with his oratorical style). His hands are animated while he speaks, but drop with a thud against the lectern as he pauses, fingers interlocked.

The rhythm of his silences follows the rhythm of his speech. Even without hearing a word, we can tell by watching the crowd how his rhetoric moves between introductory remarks, political self-congratulation, and exhortation, before ending on a note of overwrought patriotism. The accompanying silence in the room is mesmerizing, both for its depth and its duration. Here is a man who can hold an audience for over an hour, and, I’d argue, comes pretty close to holding an audience for half an hour without saying a damn thing.

How much of the negative space that we experience do we throw away as soon as we can see where the positive space begins and what do we lose in the process? I think it depends on what it is we’re experiencing, but my guess is regardless, it’s more than we think.

The Measure of Man (and Wife)

sideboob scales

Only once have I ever seriously considered getting a tattoo and it was in a dream, but what a tattoo it was! Almost every surface of my body was covered with some sort of graduated scale: one arm bore a metric ruler, the other its English equivalent; my elbows and knees measured angles and my cheeks were marked in such a way that I could determine the volume of liquid in my mouth by their stretching. When I woke up, I toyed briefly with getting a scale tattooed on my abdomen to measure the aging of my body. A perfectly accurate scale would stretch with the inevitable appearance of a gut and later sag as my skin lost its elasticity and my gut its girth in my later years. What a depressing thought.

There’s something infinitely fascinating about anthropometric graphics, especially historical ones that overlay scientifically and/or proportionally iffy mappings and measurements over the body. Despina made the point this week that everything we create is anthropometric in nature—our sense of scale exists in relation to our bodies, to our hands, to our particular sensory apparatus. No big surprise there. The problem, of course, is that when you mass produce something—say you’re an industrial designer making a table—you do so for the average body. A 60cm tall table might be ideal for the majority of people, but the extremely short and the inordinately tall on either side of the height distribution curve are shit out of luck.

Antrhopometric graphics

Vitruvian Man and his French cousin Le Corbusier’s modulor are abstractions and averages of our bodies’ proportions. As our bodies are abstracted, so is our experience of the world. It’s possible that Americans’ totally irrational attachment to feet and inches, an attachment responsible for the loss of a $125 million Mars orbiter as well as my perpetual befuddlement when looking at motors’ torque ratings, is actually an attachment to a more personal way of understanding the world.

While the meter owes its origin to the distance from the Equator to the North Pole (it was supposed to be one ten millionth of that distance), the foot’s origins, as its name suggests, are humbler and closer to home. It makes sense that since we’ve always seen the world as it relates to us, long before platinum-iridium bars we measured it with our bodies.

The wikipedia entry on the history of measurement has this to say:

The common cubit was the length of the forearm from the elbow to the tip of the middle finger.


It was divided into the span of the hand (one-half cubit),


the palm or width of the hand (one sixth),


and the digit or width of the middle finger (one twenty-fourth).


If Noah had been cursed with short arms, his ark with all its cubits and spans might not have fit all the animals he was responsible for saving. But imagine an entirely bespoke world, where my dining room table was 29 of my inches off the ground and yours was 29 of your inches off the ground. It would be a nightmare to coordinate measurements but it would also transform the world from human scale to this human scale or that human scale.

Which only highlights the utter anachronistic idiocy of the English system, as it is now as much an abstraction as the metric system, only more unwieldy. And it was this that led me to my project for this week.


I really have no sense of English length units. My wife has no sense. [Drum hit cymbal crash] Of metric units, of metric units. This has proven a problem on more than one occasion when only one of us had access to a measuring device. For instance, I was out looking for a bookshelf to fit a narrow space and found one on the sidewalk I thought might work but hadn’t measured the space exactly so I couldn’t be sure without calling my wife. Even with the exact measurements of the space, I could only guesstimate the shelf’s measurements by eyeballing, and I didn’t want to carry the thing ten blocks if it wasn’t going to fit.

To make sure this would never be a problem again, I sanded off the scale on one side of a standard yardstick and replaced it with two scales based on separate measurements of three parts of our bodies available in duplicate to ensure ease of use: the length heel to toe of our feet, the width across our palms from index knuckle to pinky knuckle, and the width of the middle segment of our middle fingers (which were identical at 3/4 in. and thus provide us with a common if slightly inconvenient unit of measure). I tried to select measurements that would not vary too much with time or normal wear and tear. The result is a ruler that allows either one of us to easily convey measurements to each other remotely by converting between units of our bodies into standard units of measurement. And my wife thought it was sweet in an OCD kind of way.

Feeling chuffed with this idea and my yardstick, I realized that my system would break if neither of us had access to it, but then I remembered that I’m a high technologist and dutifully banged together an online version:



Wikipedia also says that the yard may also have come from the measurement of the waist. Note the 36 inches. I’m the fucking Vitruvian man.


Trust Fund Thursdays

Design an experiment to take you out of your comfort zone in terms of how you relate to your body and space.

That was a no-brainer for me. I hate taking pictures of people I don’t know. I’m not sure why it makes me uncomfortable, but it does. I’ve lived in some of the most bizarre and photogenic (and crowded) places in the world but have frightfully little photographic evidence of anything other than their architecture. I set out on a beautiful spring day to photograph random New Yorkers. My initial idea was to stop in front of people, plant my feet and raise my camera and, without saying anything, take their picture and walk away. This quickly stopped being uncomfortable, especially since no one seemed all that surprised or upset. My body is unexceptional in the space of New York—I’m one of the crowd. In Asia, my face instantly identified me as a foreigner and it was the motivations that I imagined my subjects could attribute to my picture-taking combined with the total unpredictability of their reactions that made me so hesitant to uncap my lens.




I considered forcing an interaction. It might make me uncomfortable to act strangely in front of these anonymous New Yorkers. I could express some emotion or attitude when taking the picture (disgust came to mind, grimacing once the picture was taken and shaking my head sadly as I walked away). That seemed unnecessarily confrontational and with the current state of my back, I didn’t want to risk a scuffle. The threat of bodily harm, whether real or perceived, is a whole different universe of discomfort and I’m no Marina Abramovic. I could also go the other way and be extremely friendly and use the element of surprise to my advantage. This seemed like a better idea, so I stopped random people and asked to take their picture.


That didn’t make me uncomfortable at all and really didn’t involve my body and space so much as it did my mind. I had a prop (the camera), it was a beautiful day, and the force of my delivery made people almost universally acquiesce to my request. Having a purpose emboldened me to overcome the discomfort of getting close to a stranger, looking him/her in the eyes, and making a request. It was like asking for directions. The only no I got was from a couple of European tourists who seemed to think I was running a scam.

I couldn’t exactly replicate the conditions of the initial discomfort I set out to overcome in New York, so I abandoned the idea and enjoyed the sun.

Several days later, I was lying on a grassy hill in Central Park, reading a magazine after a doctor’s appointment in Columbus Circle. There weren’t a lot of people around. A couple was lying on a blanket to my right, calling frantically to their two dachshunds Dottie and Dixie whom the combination of sun and open space to explore had apparently rendered deaf and impervious to a proffered frisbee as they disappeared down the hill, their collars clinking madly. To my right, two Puerto Rican girls in tight jeans and big sneakers discussed the probable futures of their classmates. Somewhere behind me, a woman with a voice hoarse from a late loud night exclaimed, “That’s soooo fucking funny! Today is sooo fucking trust fund Thursday,” which was met with clapping and hooting laughter. I didn’t turn around.

I read until the people to my right finally corralled their dogs and packed up their blankets and the Puerto Rican girls had run out of classmates with prognosticateable futures and turned separately to attending their cell phones. Another explosion of laughter from caused me to look for its source, which I discovered was three hipsterish white women and a slim and even from a distance obviously gay black man. I found myself disapproving of them, if for no other reason than that they seemed a New York cliché—the girls in leggings, ratty tee-shirts, and oversized sunglasses, the guy snarking comments that would set them all off laughing—and they were having much more fun than the afternoon and their surroundings warranted. I realized I’d found my discomfort.

I stood up, brushed the wet grass off my pants, and walked over to them. “Can I join you?” To my surprise, they burst out laughing, “Of course! We’ve had designs on you all afternoon. Sit, sit. Here, have some champagne.” In addition to a couple bottles of champagne, they were drinking something green out of plastic cups. “Are those mojitos?” Apparently, the Mexican man who had come by an hour earlier selling ice cold water and gatorade had an unadvertised happy hour special hidden in the rolling suitcase he trundled behind him. I sat with them for over an hour, earning the epithet “Ambitious Alex” in the process, receiving several hugs, handshakes, and a lot of playful innuendo that made me terrifyingly uncomfortable while thrilling me at the same time.

I don’t like to be noticed in unfamiliar social situations until I’m confident I understand their dynamics. It took me almost six months to make my first post to the ITP student list. In this situation, however, I made myself the center of attention. I had to talk about myself without a good idea of what sort of tone to adopt or what reaction to expect. I had to shape my first impression, as I could not rely on having months of repeated interactions over which to hone it. I wanted Sam, Michelle, Deb, and Stefan, whom I liked as soon as I sat down, to like me back.

I only performed this experiment once, but I plan to try it again the next time an opportunity presents itself. I learned that what makes me uncomfortable is not how I relate to my own body and space but how my body relates to other bodies. Which is what led me to the idea of measuring those parts that vary most from body to body for my embodiment object.


As a kid, I was always a little anal when it came to toys. I never lost a game piece, and somewhere, there are probably still untouched sticker books, rolls of caps, packets of photosensitive paper and countless other long-forgotten expendables that I saved myself out of ever using. Childhood doesn’t last for ever but some of its habits do, and despite missing my calling as an environmental crusader, I still find myself deliberating much longer than warranted before replacing razor blades, changing guitar strings, or “premiering” new shoes.

Looking through the vast online materials repositories (smallparts, matweb, inventables), I found many with surprising properties—translucent concrete, foldable porcelain, memory wire—which made me realize that materials engineering must be pretty fun: in order to achieve X, I need a material with a bunch of properties—physical, chemical, structural, economic. Finding that material requires a combination of research into existing materials and applied chemistry, physics, and manufacturing. Materials engineers are like the Special Forces of the world of stuff (and in this analogy I’m the fat kid on the couch who just watched a be all you can be commercial). Which is all to say that when faced with the challenge of creating my own material, I started out with two goals: that it have surprising characteristics (like silly putty or magnets) and that it be reusable.

Despite years of science instruction from teachers desperate to convey science’s innate coolness, I managed to make it through school without ever encountering non-Newtonian fluids (or “oobleck” in middle school science speak). Quicksand is a good example of a dilatant or shear thickening fluid, ie, a fluid that behaves like a solid when subjected to shear force. Silly Putty, it turns out, also has dilatant properties, which is why it stretches if you pull it slowly but breaks if you yank it quickly. Other more complex dilatants are used in automotive power transmission applications. The DoD has been researching armor applications for years, and I suspect that D3O’s shock absorption technology relies on dilatants. The most readily available and accessible example of a dilatant is a 2:1 mixture of cornstarch and water. I made some to play with, thinking it might be interesting to fill a balloon with it. It wasn’t (it’s hard to subject the entire contents of an elastic sphere to any significant shear stress), but it is fascinating stuff to play with. I took slow-motion video of it turning solid as it pours and of its state changes as I dragged my fingers through it.

Moving on, I returned to online repositories of materials for other inspiration. I realized that not all materials are invented through brilliant accidentsa la vulcanized rubber; many are “discovered” by when existing materials are shaped or applied in new ways. Rather than trying to create a reusable material with unexpected physical properties from scratch, I set out to find one that wasn’t in any of the online repositories. It was, it turned out, readily available at K-Mart.

Moon Sand is a moldable substance that feels and looks like wet sand but is in fact dry (and never dries out). A little research turned up this patent, that along with a detailed recipe for Moon Sand, reveals that it is actually very fine sand coated in wax. This allows it to stick together when molded or sculpted but also gives it some other nifty properties. If you heat Moon Sand for about half an hour in an oven, the wax melts and the sand sticks together a little more permanently.

Armed with this knowledge, I set out to explore some more of its properties. I assumed that the wax’s adhesion to each sand particle must be greater than its adhesion to itself (otherwise heating the Moon Sand should have produced a puddle of wax and a pile of ordinary sand) so I reheated it and while it was hot broke it back apart. When it cooled, it had returned to its original, pre-baked state—reusable! What are some of wax’s other properties? One obvious one is that water beads off it. This seemed promising. What if Moon Sand is water proof, if it keeps its moldable properties even underwater? Turns out it does! Amazing! Unexpected! And as soon as it dries, it’s back to it’s original state with no visible or tactile deterioration. Reusable! The Moon Sand marketing dwells on how it allows kids to bring the fun of outdoors indoors without making a mess that mom can’t clean up with a single swipe of the vacuum cleaner. This seems like a missed opportunity—this is sand you can play with in the bath tub! So, it turns out it’s not a missed opportunity at all, it’s variant differentiation: check out Aqua Sand, a branded version of hydrophobic sand that was developed to clean up oil spills.

For my final material exploration, I ordered a pound of sodium acetate (C2H3CNaO2), a non-toxic salt used to flavor salt and vinegar potato chips and for a variety of industrial chemical applications as well as in hand warmers, which is how I knew about it. When it’s hydrated and heated, a solution of sodium acetate can be supersaturated and then supercooled at room temperature. This means that thought it ordinarily freezes at 58ºC, it stays in liquid form well below that temperature provided there is no nucleation center for crystal formation. This same effect can happen with distilled water (normal water contains impurities for crystals to form around) as this meathead scientist discovered in Thailand:

Sodium acetate comes in two forms: trihydrate (the kind that melts near room temperature) and anhydrous (the fine powder that doesn’t). The stuff I bought for a dollar was labelled trihydrate but I discovered was in fact anhydrous when it caramelized in the bottom of a frying pan. I brought a pan of water to a boil and then turned it off, spooning and stirring in the powder until no more would dissolve. I then poured it into a clean jar and have since “set it off” and “reset” it about twenty times. Reusable and suprising!

There are a number of applications I can think of for this stuff. It’s used in hand warmers because its crystallization is exothermic (which makes sense: if the liquid is cooled way beneath its freezing point, when it freezes, the kinetic energy of the liquid has to go somwhere). A basic application would be to make a waterproof fabric filled with a thin layer of the stuff to make a hand-warming clutch for chilly winter soirees. A more involved application might be as a security measure: keep a diamond in a tank of the stuff and if someone tries to get into it, it solidifies. In that sort of a situation, it might make sense to use another chemical with similar properties but a much higher melting point so that the heat it gave off when crystallizing cooked the would-be thief alive! That’s got to be worth a multimillion-dollar defense research grant.

« Previous Entries