Introduction: Relief in Shadow
Have you noticed that the shadows on blinds can make a grayscale gradient? I have. And if you’re anything like me, you get excited whenever you see a naturally occurring gradient.
I realized that if you could control the shape of each blind, you could control the grayscale value along the strip. The more shallow the strip, the less shadow, and the brighter the value. The deeper the strip, the more shadow, and the darker the value. By shaping each strip to match the intensity values of a given image, you can reproduce that image in shadow, without painting, printing, or any pigment at all.
This Instructable is similar to my other relief Instructables, in the sense that we are converting a 2d image into a kind or relief map of intensity values. But in this case I am slicing up the relief into vertical strips.
- an image – I’m using a tintype of my brother created by the artist Kari Orvik (http://www.kariorviktintypestudio.com/)
- thick, rigid paper. I used Strathmore's 400 series. l
- acrylic support structure
- laser cutter
The general workflow is that I'll translate the columns of the image into a vector drawing, based on the pixel intensity. I'll then cut these shapes out of the paper with a laser cutter, and feed them onto a support structure.
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Creating the Strips
Each strip of paper represents one column of the image. The depth of the strip at a given point corresponds to the intensity of the pixel at that point. I wrote a program that, at a set column spacing, would convert the intensity values of each pixel in the column into x-y coordinates. I included an offset to allow for an acrylic support structure. For example, a pixel value of 0 (black) would be converted to 2 inches. A pixel value of 1 (white) would be converted to 0.35 inches. This .35 inches is to allow space for the support structure to engage with that strip. All the points are connected and written as lines to an SVG file. For more on converting data to SVG files, check out my instructable https://www.instructables.com/id/Creating-a-Vector...
It is also necessary to close of each line by adding a top, bottom, and left side, and to add a slot for the acrylic support structure (next step). These are the rectangular slots at the top and bottom of each strip.
I cut each strip using an Epilog 120 watt laser cutter. I could not find a speed/power/frequency combination that would eliminate burn marks from the edge of the paper entirely. I ended up using 95/20/1835.
Step 2: Acrylic Support Structure
Using a laser cutter and eighth inch acrylic, I created a kind of comb structure that had grooves for each paper strip. I chose a spacing of about 14/strips an inch. This spacing was a balance between the level of detail (the more strips the better) and the fragility of the support structure (the more strips, the thinner the comb prongs, and the more fragile the support). The comb controls the spacing of the strips, and helps to point each strip in the same direction.
The speed and power for the cut were tricky to find. The prongs are so close that the heat from the laser tends to linger. Too much power and the comb would curl up, or the prongs could fuse together. To little power, and the outside shape of the comb would not cut well. The settings for a 75 laser Epilog laser were 20 speed, 45 power, and 5000 frequency.
Step 3: Assembly and Installation
After laser cutting, I fed each laser cut strip onto the two acrylic supports. Once all the strips are in place I installed the piece by hanging it with monofilament from the ceiling, using a uni knot to tie the filament to the acrylic support. In order to get the image to show, I backlit the wall behind the piece. As long as the background is brighter than strips of paper, the image should resolve.