I hung out in the Art area, between the dis-information desk and TOOOL.
My portable holography apparatus is a simple single-beam Denisyuk setup. It is the simplest and most stable configuration, and creates a white light viewable reflection hologram.
The laser is a Coherent Compass 315M laser. Its a 100mW frequency doubled YAG. Its one of a large set of lasers which hit the surplus market several years ago from plate burning machines. The 315M's are surprisingly stable, their coherence length is about 30 feet, which is larger than anything that will fit on my optical table. One simply does not have to worry about matching beam path lengths.
The laser takes about 5 minutes to warm up and finish its self-calibration dance, so you have to leave the laser running, and add a shutter in front of the laser.
My shutter is a piece of metal from an anti-shoplifting tag super-glued to the needle of a mechanical meter. It hangs quietly, and when voltage is applied swings to one side without any clicking to create vibrations.
The shutter is controlled by a Tandy 200 laptop. It was manufactured in 1985, and has an old-school gray on Gray LCD. It does not emit light, so it is inherently safe in a dark room. It also has a cassette interface, which features a relay to control the motor. IE: it has a relay output, I just plug it into the circuit for the shutter, and the command in BASIC is "motor on" and "motor off". For HOPE I had a simple program which waits for a key press, waits for a minute for all the vibration from loading the film and object to settle down, and then does a 1/2 second exposure.
So the first day, I explained holography to lots of people, and forgot my darkroom slot sign up sheet. At 1:30 I ascended to the Budapest room for the first attempt at doing the dark room thing.
It was possible to easily turn off all the lights in the room... but the doors are frosted glass. MEH. But I did not carry 80 pounds of stuff all the way from Maryland on my back to not make holograms, so I tried it anyway. All the stray light coming through the doors (sorry, I failed to take pictures...) did not actually fog the film. So we went with it.
We did eight attempts, and got several visible images. Sort of... The wash was inadequate, so there was bleach still left in the emulsion, and over the next several hours all the holograms faded. When I was testing in my basement last weekend, I used the real apparatus for exposing the holograms, but I used my usual darkroom sink with running water to avoid making an epic mess. My tap water at home is also notoriously acidic (it eats copper plumbing) and I believe that acts as an "anti-printout" bath so the holograms don't fade as much.
So, first some pizza, and then an emergency trip to Target to buy vinegar and a gallon of water (I needed the jug more). I also need to re-think how to clean up. The developer looks like thin lemonade, yellowish water. BUT in a couple of hours, or as it dries up, it turns purple. It stains when you least expect it...
This was the big day of the conference, as far as population.
The chemistry was in a better mood, though the holograms were still a bit too purple. However the vibration problems were worse. We did nine attempts, and again got several good images. I was surprised how well people's keys and padlocks worked. My stuffed animals were not especially happy. I call it the floating nose effect, the animal is resting on the film holder so its nose is sufficiently stable, but the rest of it is either sinking slowly or blowing around in air currents so there is no image. Just the nose.
I ran out of handouts...
The chemistry is finally perfect. The holograms needed more time in the bleach. The normal rule of thumb is bleach till clear, and then 30 seconds more, for a total of about 1:30. However judging the clear-ness with the safe-light is difficult. Going for 2:00 was much happier. By now, I'm out of developer and the bleach which is usually blue like windex is looking green with black bits.
The acetic acid in the final wash was also much happier, and effectively reducing the printout effect. It was visible because the corners of the film tended to stick out of the chemistry, and the corners were going dark.