I guess this question has two parts. I'm prototyping a solar energy device, part of which is a light pipe to transport the collected solar energy, about 300 - 2500 nM. I'm planning on making this from a flexible tube filled with a highly refractive liquid, stoppered at each end with clear plugs. It looks like the materials I should be using are: Tube: Teflon (PTFE, FEP, AF 1600, AF 2400) in that order of desireablitity, lowest to highest. The AF 2400 has a refractive index of 1.29, which is the lowest of any polymer. Apparently. Core: Mineral oil / liquid paraffin. Plugs: Acrylic or normal glass. Thoughts? Also, where would you suggest I try to find these? (I have the mineral oil already) Keeping in mind that I'm in Madrid, Spain. Getting this to work would make a huge difference to solar microgeneration, as transporting the energy is currently a bit of a nightmare. Thanks heaps, Daniel.