This is a project conceived for the Market Street Prototyping Festival in San Francisco, April 2015.
Creators include Sabrina Habel and FICTILIS

RAINBOW PRISMATIC EXPERIENCE

The Rainbow Prismatic Experience in its simplest physical form is a large cluster of hanging prismatic material suspended from above. However once placed on the street has the power to transform the entire surrounding landscape. All of a sudden rainbows appear over the building walls, sidewalks, pedestrians and your own body. Or even more unexpected: the sight of rainbows at night, refracted by streetlights and automobile headlights.

The main goal of the Rainbow Prismatic Experience is to create unpredictable moments of magic and beauty on Market Street. The rainbow is a symbol with many positive associations such as hope, creation, divinity, luck; often construed as a bridge, a liminal space, harmonious and transformative. San Franciscans, representing a culturally, racially, and gender-diverse city have adopted the rainbow to represent their identity. While the rainbow-flag is synonymous with LGBT Pride and ‘PACE’ international peace movement, an actual rainbow, created from light refraction, is even more inclusive to all people creating an opportunity to connect emotional and spiritual to the rainbow as a natural phenomenon.

The Market Street Prototype Festival provided a testing ground to determine location and construction based on sunlight/wind and adjacent surfaces to reflect rainbows.

Step 1: Materials

Dichroic film in "Blaze" and "Chill" 4ft wide and sold by the foot (see photo)
Diffraction Grating sheet 1,000 lines/mm Linear 5 Foot x 6 Inches Wide
Diffraction Grating sheet 13,500 lines/inch - Double Axis 5ft Long x 6 inches Wide
Calendared Vinyl Sheeting .004 x 54" (4.5ft wide) and sold per yard (3ft)
Sewing Machine
Thread
Nylon rope 1/8th inch
Grommets/Grommet punch 1/4th inch
Zip ties
Good pair of scissors
Painter's tape
Fabric gloves for handling dichroic film
Large, flat, clean work table
Measuring tape

Step 2: Design

After an exhaustive materials search including acrylic prisms, chandelier crystals, sun catchers and so forth we consulted the Exploratorium in San Francisco for suggestions of prismatic materials. They recommended Dichroic architectural film and diffraction grating film. Since this is a prototype we decided to use both.

Because the prototype required suspension points on Market Street we hunted for three available suspension locations in a triangle formation. We found a crosswalk light, street sign, and lamppost in a corner location with satisfactory amounts of direct sunlight. We designed based on the constraints of that specific location. In the above photo you can see the scaled map of the location with distances and circumferences marked out, and from this we were able to judge how much material we needed.

Due to the high winds and the poles we have as suspension points we used nautical sail-rigging to inform the design. The angled triangular jib-sheets were the type of sail formation we found most appealing and created a tiny and approximate model. We researched sail repair and found common sail construction that could be applied to the material. We also researched knot tying for appropriate knots to at each suspension point.

Step 3: Fabrication

Be patient and use good judgement - the materials used in this can be very expensive and show wear/tear and mishandling very easily. The dichroic film will show finger prints, nics and bends, so handle using clean gloves. Lay things out and make sure they are the way you want them before adhering or sewing anything.
Measure (carefully and excessively) and cut dichroic film and vinyl sheeting down to matching triangular sail shapes
Either carefully peel away the dichroic film backing and affix to the vinyl sheeting or simply stack the vinyl on top of the dichroic film (The photos show the dichroic film with the backing still attached. When the backing is removed the film is reflective and transparent - if you opt for no backing, be careful of air bubbles!)
Use painters tape to keep edges aligned, you will be sewing the material together eventually
Make sure your sewing machine is in good repair and use some test material to do sewing trials, testing thread tension and spacing
Sew 1/2" to 1/4" from each edge of the materials around the perimeter of the triangle, securing the vinyl to the film
Repeat for each triangle and remove painters tape
Follow instructions for applying grommets to each corner of each triangular sail
Follow instructions for applying grommets to each corner of each rectangular diffraction grating film strip
Now your materials are ready - the Installation step will entail the rest of the process

Step 4: Installation

All the prepped materials are easily rolled up in one big roll and one bag. I installed everything myself on a 12ft ladder and had an assistant on the ground handing me materials, keeping the ladder steady, and keeping pedestrians from interfering. Depending on where you are installing this a scissor lift might be a better choice than a ladder.

Using your design and model tie up each sail from its three suspension points:

Eyeball the area and measure out the nylon rope for the first sail - err on the side of way more rope than you need
Use bowline knots to tie off the rope at each grommet and each suspension point, large zip ties can be used around the poles to help further secure the rope and prevent slippage down the pole
On one side of each triangle use clear small zip ties to attach the diffraction grating film strips to the sails using grommet holes as connection points
Repeat the previous steps for each sail you would like to hang
Double check each knot's tightness and snip off excess rope

Step 5: Interaction

We learned a lot with this prototype. It did not require any instruction for the viewer but the following considerations should be planned and tested thoroughly by the artist before installation:

Track the sunlight path over the area and the angle at which the sunlight shines. These observations will help you make the most of the sunlight and give you maximum rainbow potential.
Track the amount and general direction of wind. If your area is extremely windy you may want to angle the sails to flow with the wind instead of against it and perhaps reinforce each corner of each sail to prevent stress and tearing.
While the dichroic film has the most dramatic color effects, the diffraction grating film makes the best full rainbows.

On the day of the Market Street Prototyping Festival our prototype was initially not properly angled to produce maximum rainbows. Additionally it was not durable enough to withstand the 10 to 18 mph wind of the location. One by one, the sails ripped and fell as the wind increased (pictured above). This however, was a great learning experience. Once the sails fell and dangled from two suspension points they were properly angled for maximum rainbows! Unfortunately the reflective-ness of the material was blinding on-coming car and bicycle traffic. Despite that potential hazard, we learned that the sails were suspended too high up. People enjoyed looking at themselves in the prismatic reflection of the material, taking photos, and just being in general awe of its effect and reflections.

While the installation only made it through one day, we feel that future iterations can be wildly successful and just as magical as intended. Please enjoy photos by the public and some shared on Instagram.