Neil Kandalgaonkar

hacker, maker of things


halowall test by Neil

This all started when I saw a rainbow on the ground. It appeared after some workers had finished sandblasting there.

I researched this phenomenon and found out it was a “glass bead bow”, a special kind of rainbow formed by glass microspheres. It’s just like the rainbow you see in the sky, except it’s more intense and at a tighter radius than a water rainbow. But because it seems to be embedded in a nearby surface, it’s more obvious that the rainbow “follows” you around, and is centered exactly on your shadow’s head. It looks just like a rainbow halo.

I thought this could definitely be a Thing we could bring to Burning Man. The Black Rock desert has intense sun, and I like the idea of art that uses the environment. But mainly because I just love colors and light and science and I don’t care if it isn’t art exactly. But, despite that, it ended up illuminating (ha ha) some surprising aspects of reality anyway… in many ways some disturbing ones.

And, deep down, I wanted to do “an art” because I was afraid of asking others to believe in my ideas.

Burning Man and dust, dust, dust

casey hammer by Neil

Right from the start great people jumped in to help. I started working with Casey Hutchinson (nnooiissee) to make this happen. Casey was attracted to constructing the thing, and I focused on all the R&D and planning. We got some fantastic support from the Ardent community, and built the whole thing at NIMBY.

On the face of it, this seems like a simple project, but there were a hundred details to get right. How to communicate to Burners what you were even supposed to do with it? Exactly how should it be oriented to maximize the sun? What about ensuring that people can’t climb on it, while also making it sturdy enough? What medium should we use to hold the beads? And how do we protect that surface?

Some of my favorite moments were during build season. When I showed the first working prototype to Audrey, she exclaimed that it was going to freak people out. And then, when the first tall board was ready, another random person, working on her own art project, walked by and glanced at what I was doing. She almost tripped and fell over when she saw shimmering bands of color, like it was something physical in front of her.

Except, on playa, those lovely panels had to be placed behind plastic, which reduced the rainbow effect and attracted dust. I didn’t plan adequately for that, and either Casey or I spent some time cleaning the damn thing every day. I’d also brought a solar lamp with me, but (a) it broke (b) it was nowhere near bright enough for nighttime viewings. On the whole, while a handful of people actually got what it was about, for the most part it was a bit disappointing. It was charitably described as “subtle”, and in retrospect, it was never going to compete with giant metal sculptures that shoot fire. But those who saw it at the right times were delighted.

Decompression: victory!

halowall at decom by Neil
Couple enjoying the wall, plus lots of friends in the background.

But then we knew how to make it work. We took this to SF Decompression, the post-Burning-Man event, in a slightly different form, with better results. Cubes and Eden joined the team for the SF Decompression run. I borrowed an extremely powerful light bulb and learned enough about things like ballasts to make a super-intense light that would appear to be a point source, just like the sun.

The day of Decompression was absolute madness as practically everything went wrong, but by the end of the day it worked… perfectly. People loved playing with it. The effect was as stunning as we’d hoped, and Eden made some graphics that guided people to use the wall in the right way. You can see some of this in the final videos in the photoset below.

An unintentional perception test

And yet there was something else a little bit disturbing. Some people were simply unable to see the effect. At least half of the people were bewildered, until the rainbow was pointed out to them, by us or by their friends.

The rainbow is not subtle. It’s hard to capture in photos, but if you are a few inches away from the wall, it’s overwhelming. We sat on the sidelines wondering what was wrong with people.

halowall and israeli kids by Neil
These Israeli kids demanded explanations of what was going on and why they couldn’t see anyone else’s rainbows.

This is why you bring your art to Burning Man or Decompression. People don’t politely look and move on, sometimes they run up to you and hug you and demand more.

You see, the weird and wonderful thing about these rainbows is that you can only see your own. (Another favorite moment: a bunch of hippie kids hugged me and demanded to know why they couldn’t see their friends’ rainbows.)

If you are even a few meters away, it looks like a bunch of crazed people are playing with their shadows. (If this thing had any artistic merit at all, that’s the thing I was going for, by the way. That’s why it’s built so large, and with silhouettes already embedded in it - to emphasize that you have a unique perspective that no one else can know or share.)

My theory: the only people who “got it” were ready to perceive new things about the world. Photographers, artists, scientists, and the Decom volunteer community - they all got it. An engineer who brought his solar car to Decom didn’t even believe me when I told him that half the Decom-goers couldn’t see it. People who came to Decom for a party, to dance, to see and be seen, to wear clothing they could never wear elsewhere - they tended not to get it. If you asked them “and is there a giant shimmering rainbow in front of you?” they’d jump and say “Oh yes!” Somehow, I think, they carried their initial conclusion (featureless black wall) forward, and the very different stimulus they were now getting was just ignored, because they’d already concluded what it was.

It got to the point where I could easily predict who would get it. A couple of volunteer Decom staffers were sitting nearby in a golf cart squinting at this bizarre behavior, so I insisted that they get out and try it. I knew that, as longtime Burners and community-minded people, they’d be able to see it. One of them did, and when she got close she immediately started giggling, and returned back smiling to report what she’d seen.

I’m not sure what to do with this knowledge. It seems that we have a pretty good test to distinguish people who look at the world with slightly fresher eyes, who are alive to new and surprising experiences. This happens to be exactly the sort of person I like to have around me, so maybe I need to make a pocket version for all social situations.

Build diary

The photo set on Flickr tells more of the story, especially all the stages of building and testing.

halowall experienced by Neil
It is impossible to photograph someone else’s experience of HaloWall, because their rainbow is visible only from their vantage point.

So watch for the moment when I pass behind them – you will see a rainbow that is similar to what they are seeing. They are much closer to the wall so they are seeing circular rainbows that are two to three feet in diameter, tightly encircling their heads.

But neither can these two people see what the other is seeing.

angle-diagram by Neil
Diagram produced for the funding proposal, showing how the glass bead rainbow (glassbow) appears at a 22 degree angle.

A natural "water" rainbow appears at the much wider angle of 42 degrees. In most cases this covers much of the sky and the ground. This is why you almost never see it as a full circle – the dry ground gets in the way, or the atmospheric conditions don’t hold over such a large area. Full-circle water rainbows are sometimes visible from airplanes or very high buildings.

halowall sunlight trial 1 by Neil
Initial prototype for HaloWall, testing different types of glass beads.

Look at the upper-right hand quadrant and you’ll see there’s part of a rainbow, the arc’s center at the camera. However, unlike a rainbow formed by water droplets, this one is formed by glass spheres, so the curvature is much tighter. Then just imagine that effect extended to an 8’ high x 24’ across wall, so you see the entire circle of the rainbow.

Here’s an example of the full circle, captured by legendary MIT physics prof Walter Lewin. And see here for the science.

Walter Lewin and his TA’s built a demo of this for their introductory physics class, but as far as I know nobody’s ever tried to make a really large scale version, let alone one that will work in the outdoors and in the desert.

halowall design 1 by Neil
This is the design I submitted to the Org. It was massive in size so that it would work from many angles.

We didn’t get funding.

tests on cardboard by Neil
I tried many ways of adhering the glass beads to the black surface. Many were patchy or not durable enough.
tests on cardboard by Neil
The best-testing method used special road paint, designed to hold optical beads. Rolling with a heavy pipe made an even surface. (The scratched areas are deliberate damage to see how much abuse it would take.)
tests on cardboard by Neil
halowall design 2 front by Neil
this is the revised design which got built. Note that it is smaller but has two sides, for viewing at two times of day. Also, there are now silhouettes embedded in the wall, for various thematic reasons, but also as a "defense" against burners who might want to add their own art to an apparently blank wall.

The silhouettes are all Creative Commons licensed images from Flickr. Credits will appear on the website when it’s finally up.

The original photos were:

Silhouette of a family of five by Robert Crum

From the Ă…lesund Aquarium by Federisco

School’s In by Looking Glass

Untitled work by jaysk

halowall 2 design back by Neil
The design for how the thing stays up. We stole most of this design from the Ephemeral Graffiti Wall project.…

constructed wall by Neil
This is Sam standing in the picture just for scale. He has nothing to do with this project, he just happened to be working on his robot in the shop that day
constructed panels by Neil
constructed wall by Neil
Casey and I made the panels, then I constructed the legs, and then Casey actually built the wall while I had to go to a family function. Here’s the result
painted panel by Neil
Ardent camp staging and Carbon Garden’s platforms in the background.
constructing panels by Neil
the panels are saturated with ballistic sandblasting glass beads, then rolled to grind them in

Ian Baker (aka raindrift) is fiddling with the generator in this shot, if I recall correctly.

halowall test closeup by Neil
This was my project at Burning Man 2009. Artwork that produced a halo around your shadow.

Wait! Don’t go to the next photo. Please see the whole HaloWall set instead. All will be explained.

halowall test by Neil
printed stencils before cutting out by Neil
By staggering them together I got 64 square feet of stencil into a much smaller area of paper
painted panels and silhouette stencils by Neil
working late at night, started to pin stencils to the bench for company
silhouette stencils by Neil
pinned, and after painting
complete panel – other three in background by Neil
shop space is getting a little tight
completed panels by Neil
They have different textures – it took me a while to perfect rolling technique over a large surface. The one with vertical stripes used a smaller pipe which didn’t extend over the whole surface.
halowall test with one complete panel by Neil
Mella and David Fine take a look at their rainbow halos
halowall test with acrylic covering by Neil
rainbow is somewhat attenuated, but that day’s sunset was also cloudier.

We’re also getting reflections from the sky and nearby items.

halowall test with acrylic by Neil
we drilled the acrylic and screwed it on with wide washers. In retrospect, this warped the acrylic too much and allowed more warping on playa. Still I like the "borderless" effect.
edrabbit in halowall by Neil
Edrabbit observes his rainbow - mine is visible cutting through his shadow’s head
halowall test by Neil
it’s packed by Neil
casey (aka nnooiissee) shows his level of enthusiasm at load-out at 2:30am. We were drilling and applying acrylic until about 2:29am.

It packs pretty flat though. This was IKEA art.

it’s done by Neil
And loaded in the trailer.

More details in a few weeks.

halowall’s floofy by Neil
When you late-register art at the Artery, they send you out with a dude/dudette on a golf cart and a GPS, and you bang this "floofy" into the ground, which is a CD with your artwork’s name on it and some pink bristles so you can find it again.

They take a picture of you doing it, I think to prove that you accepted this spot.

By amazing coincidence I got a spot very close to 2pir, which you can see in the distance (the yellow perimeter fencing). We were also 200’ from Esplanade. It was incredibly lucky but also a bit of a problem, as HaloWall requires close investigation, and there were lots of other things to distract passers-by.

halowall from north by Neil
The whole thing looks a bit flimsy but is quite resilient once it’s all put together. We never got high winds this Burning Man, but I’m confident we could have weathered them.

You may notice that the top edge is vertical, not horizontal. This was weak, by design, so it would look like you couldn’t climb up there. Burners will pretty much climb anything they can, and we didn’t want that for this piece.

That rebar is three feet into the ground, by the way. We needed Reed/HuggyBear’s help to even extract it. Pulling rebar is approximately my least favorite thing in the world.

There is a bucket of soapy water for cleaning and a container holding a deep cycle battery there. I brought a fancy CFL light but the bulb broke in transit (and UPS lost my dusk-to-dawn circuit, THANKS A LOT.)

We never did light the damn thing properly at night. Although Ardent offered the use of generators and a work light, Friday and Saturday evenings were a near whiteout anyway.

halowall from northwest by Neil
not much too look at. Some versions of the idea had some instructions or other things in back, but in the end we opted for nothing other than pure function
halowall more of the side by Neil
halowall shady side by Neil
the side that doesn’t do anything in the mornings.
halowall morning both sides by Neil
it has two sides to catch morning sun and sunset sun, but the morning one was kind of a wash since the rainbows were centered too low.

If I did this again I’d make it so it did sunrise and sunset – rays are then horizontal.

halowall morning rainbow by Neil
just visible at the knees.
halowall morning rainbow by Neil
in the morning, the rainbows were centered on the ground. Harder to notice
halowall morning rainbow by Neil
The rainbow is faint here – hadn’t anticipated that. It’s simply a matter of density – at this angle, we are seeing a rainbow produced by fewer beads. A subsequent version should take that into account and possibly angle the wall for high sun, assuming the sun is used as a light source.
halowall silhouette in shade by Neil
I ran into another Burner randomly who happened to have owned an art gallery until recently. He demanded to see HaloWall. At three in the morning. So I cleaned it off and he brought a powerful LED lamp and it sort of worked. He and his wife were very charming. I am not much of a ravar eediot, so encounters like that are the reason to go to BM in my opinion.
halowall from far by Neil
2pir is partially hidden by HaloWall. The Gothic Rocket Ship is at far right.
me and the thing by Neil
halowall & me. I hope you all dig my awesome burning man costume.
halowall cloudy sunset by Neil
very faint effect due to the clouds.
halowall spectator by Neil
halowall spectator by Neil
the faint rainbow crossing the wall is centered on me; this spectator sees another one centered on her
halowall spectator by Neil
the specular reflections of the sun were a problem, but without the acrylic coating the artwork would have degraded the first day
halowall spectator by Neil
the faint rainbow at left is "mine", she sees something else
glassbow at sunset by Neil
the left panel got dustier between the acrylic and glass bead surface, in transit. We eventually opened it up to clean it and reattached it
halowall spectator / soapy water by Neil
Note bucket of water + a little Dr. Bronner’s – I had just finished doing the sunset cleaning. This thing attracted so much dust it needed multiple cleanings per day. Sigh.
halowall spectators by Neil
halowall graffiti by Neil
Not everyone was a fan.

The biggest problem with this art was the dust. Dust on the special surface would have killed it right away (it is unclear if it is even possible to clean) so we covered it in acrylic. But the acrylic turned out to be a dust magnet, and the rainbow effect was largely invisible if there was even a light dust coating. Also, we had more intrusion of dust around the edges than we had expected, due to warping.

So I went out there with window washing equipment, several times a day if I could. Eventually I posted a sign which explained that it wouldn’t work if it was dusty.

halowall spectators by Neil
leave no trace by Neil
after we loaded it back onto the pickup on Sunday. As stated before, we needed Reed/HuggyBear’s help to even get the bloody rebar out of the ground. We overdid it a little.

Pulling rebar in the midday sun! Art is fulfilling.

Then we mooped (looked for small bits of trash) but sort of randomly - we didn’t have time to do a super excellent sweep. As far as "leave no trace" goes, we’re probably a yellow or red zone now. Sigh. Sorry, DPW.

UPDATE: Actually we were green!

back from BM by Neil
trailer arrives at NIMBY
lamp by Neil
This lamp has the strange property of causing iPhones to make these weird fringes.
I think it’s bright enough by Neil
Testing out the bulb we’re using in our spotlight.

According to my math, at the anticipated distance, the illuminance (lux) is comparable to the sun.

Thanks to Ian (raindrift) for loaning us his expertise and materials.

Cubes & Eden by Neil
Taking a short break while setting up.
halowall nasa by Neil
These people showed up all dressed in NASA-derived uniforms. The minute we set up HaloWall they decided it was a backdrop for them to look cool against.

I had met that woman previously and told her she could fulfill all my fantasies if only she was a real rocket scientist. (She’s a photographer).

halowall nasa 2 by Neil
More of the NASA dancers.

Note this is before we removed the protective plexiglass. This made the effect somewhat stronger, but also meant the surface got thrashed by the end of the night.

Halowall at Decom by Neil
The problem with this piece, or perhaps the charm, is that you can’t tell what the viewers are experiencing. Lots of people hung back on the sidelines, convinced the people playing with their shadows were just crazy.

At Decom I could push people forward to get them to try it. Since I can’t do that for you here on Flickr, I intercut video from SF Decompression with some tests I did a week later. Note: the surfaces are completely thrashed in those later tests; the effect was a lot stronger at Decom.

halowall at decom by Neil
Couple enjoying the wall, plus lots of friends in the background.
halowall and israeli kids by Neil
These Israeli kids demanded explanations of what was going on and why they couldn’t see anyone else’s rainbows.

This is why you bring your art to Burning Man or Decompression. People don’t politely look and move on, sometimes they run up to you and hug you and demand more.

test with lamp by Neil
Set up everything at NIMBY a week after Decom since some videos didn’t come out
lamp by Neil
The gigantic 1500W metal halide lamp I built. The bulb and electronic ballast were Ian’s, I acquired everything else. A lot of it is ductwork cut, bent, and screwed together. (I really need to learn to weld. A riveter would have been nice too…) Snook also gave us an old 250W metal halide lamp to cannibalize, but ultimately we only kept part of the enclosure.

The inside is painted black, to make it more of a point light source. That makes it a lot hotter.

If we hadn’t built the shade this would have lit up the entire area at Decom. It’s about as bright as the setting sun, at these distances.

test post decom by Neil
Wiley & friend by Neil