This instructable is the next iteration of my image-to-relief project. It is similar to the water relief (https://www.instructables.com/id/Image-Relief-in-Wa... in that I created a two layer relief made up of a tinted, semi-transparent layer over a lighter colored base layer. By varying the depth of the transparent layer, you can obtain different shades of gray, and so reproduce an image. For this project, the base layer is aluminum, and the transparent layer is dyed oil.

This piece is a collaboration with the artist Kari Orvick (http://www.kariorvik.com/). Kari takes tintype photos. Tintype is a historic wet-plate collodion process means that each individual plate must be hand-crafted in the darkroom immediately before the photograph is taken, and developed immediately afterwards. Each plate has its own unique character, modifying the image that is recorded. In the last step, the tin type is dipped in a chemical bath, and you can watch the image appear before your eyes. I thought that using aluminum and oil would echo this effect.

Materials:

1/2" aluminum plate
oil
oil soluble dye
Haas Vertical Mill

Step 1: Image Mapping

Light doesn’t attenuate linearly in oil. This means you can’t just scale intensity with depth. For example, if your water appears black beginning at 1” deep, at 1/2" deep it won’t be true neutral, but much darker. True neutral might happen closer to 1/4" deep. The relationship between intensity and depth is governed by this exponential equation:

Which looks like this:

You can try to mimic this effect by modifying the curves in photoshop, or by feeding your intensity values into the above equation to get your depths. More about this is in this Instructable (which also includes some code): https://www.instructables.com/id/3D-Printed-Photos-in-Grayscale-Using-Two-Materials/

Step 2: ArtCAM and CNC

I used the software ArtCAM to generate the relief based on the mapped image, and to generate CAM. I used a profile path to create a trough around the image. After a roughing pass with a 1/2" end mill, I did consecutive finishing passes using 1/4", 1/8", and finally a 1/16" ball mill. Do not turn off the coolant with this bit! Even though there was a pool of coolant, I still broke a bit due to overheating.

Step 3: Add Oil

I had some trouble finding a dye that was completely soluble in oil. I found that pigment powders would not dissolve completely, and would settle to the bottom. I also tried oil paint, but this also wouldn't dissolve. I ended up using a candle dye. I used a smaller prototype to get the mixture of oil to dye correct.