experiments with latex and silicone casting

by lefroyobunny

For this week’s assignment I decided to try out several experiments with the latex and silicone as tools for making non woven textiles.

The first thing I made is a simple rectangular piece with an LED embedded inside. I used conductive tape for the two ends of the LED and cast it inside the silicone. Here, I used one drop of the purple dye to get a great violet for the silicone.

The results of this experiment works quite well.  The effect of the LED shining through the translucent  layer of purple silicone is very pretty. From this initial experiment, I learned that the silicone is very messy to work with, but it spreads evenly by itself quite well.

Then, I started to explore the possibility of integrating thermo chromatic paint into the silicone piece and see how it would behave. I found some dried thermo chromatic paint (aqua) in the lab and crushed it into chunks. I left it as chunks and mixed into part B of the silicone. I wanted to see the behavior of the color change of chunks vs specs of the thermo chromo paint.

I put conductive thread across different parts of the casting hoping to see the color change when I put current across the wires. The results turned out to be quite stunning. Silicone turns out to be a great insulator. It takes about 1.5amps to change the color dramatically. To see a quicker color change, I used a heat gun, and that’s the most dramatic change. I was specifically interested in the chunks vs specs and how they change color. The result was that the chunks changed colors faster than the specs. So, when I blow a heat gun across the cast, the chunks turn color faster than the other, less concentrated parts.

Next, I tried out the effects of fiber optics and its ability to direct light within double layered silicone casting. I found some fiber optic wires lying around and chopped them into small pieces with a wire cutter.

I had planned to lay them out so that they are orthogonal to the surface. However, this task was very difficult to do because it was very hard to place tiny pieces into a certain configuration, especially when the second layer of silicone was added to the mold on top of the tiny pieces.

Lastly, I put three drops of paint of  different colors onto the top of the silicone, and make swirl patterns. The intention of this is to be able to see the different colors as light is directed to the end of the fibers. It wasn’t a good idea to put dye on top of the silicone because after the silicone cures, the dye is not stable enough to maintain its form. Therefore, it rubs off on heated contact.

After the first few experiments, I gained enough experience with the silicone to begin doing more with it.  I am very interested in making stretch sensors with the silicone. My vision for such a device is one whose resistance decreases when stretched and lights up the an LED to make the visual signal of change in resistance.

For my first iteration, I use latex with carbon fiber and 4 LEDs. The latex cures more quickly than the silicone so I chose it as a “first try.” In order for this sensor to work, I realized that I need to use a lot of carbon fiber so that the fibers will touch even if the material is stretched.

This sensor works, but it doesn’t work very well. When it is not stretched, it has very little resistance (around 1k ohms) and when it is stretched, the numbers jump around the vicinity of 1M ohms. However, it seems that once the material is stretched, it doesn’t spring back to its original form. This makes the sensor unreliable and hard to work with.

The second iteration is using silicone with schoeller wool and LEDs. The appearance of the casting turns out to be much better than the one made with latex, mostly because silicone cures clear, not yellow. I layed out the schoeller wool across the silicone on either side of the LEDs.

I haven’t had the chance to test this iteration yet because I have not yet had time in the lab. I will report back with resistances and interesting things I learned once I have a chance to test it.