from bmarts this morning:
Incidentally, we’ve recently ordered some Fluorinated Ethylene Propylene. It’s one of these compounds that Dow throws under the heading “Teflon.” Hopefully it’s useful to us because it’s optically transparent (96%) and has a refractive index very close to water. So you can put it into an aqueous solution and essentially not see it. Hopefully it’s not too much of a pain in the neck to melt the stuff and shape it how we want. You can see a similar idea of a glass rod disappearing in Wesson oil and a magic trick based on the idea.