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Cryogrinding! In retrospect, obvious. I could just drop the block (well, many small pieces) in liquid N2 and smash it up. Excellent idea. I think I am getting somewhere on this.

Just encountered Dow Corning "Sylgard" products (e.g. Sylgard 306636; HIPEC® Q3-6646), several of which are at least low RI solid gels (after they cure). They are not beads, though. I wonder if there is a way to exploit their hydrophobicity to make them solidify as beads? E.g. blend them into a...

No, but I will keep that in mind. Was also thinking of using Benzyl Alcohol, which is miscible with ethanol.

Dupont is sending me some FEP--they say it is "milky." Will let you know how it goes. Teflon AF is priced like nafion--ca. 1K/gram. Some time ago I spoke to the NuSil folks, who were kind enough to send me a sample, but the stuff cured to a rather rubbery, sticky solid, which I milled to small...

Thanks! A lot of plastics, I know, are, in fact, supplied as drums of powders that are often various sizes of beads--problem may to be get them before they are turned into films. But is next to impossible to find out their appearance (clear or no) and size, except by calling manufacturers one...

P.S. It's not so much that we can't stop motion w strobes, it's that a moving specimen drifts out of the plane of focus, and we are using 3D image 'stacking' technology to produce composite photos with great depth of field.

Yes, I do realize that temperature is very important to the RI of liquids. The working temp will be very close to 20C, but I could consider a heating stage, I suppose. If a polymer of ri ca. 1.34-1.48 could be identified, however, I could get the same precision by mixing liquids of diff RIs...

You'd think, but no. This is about photography and posing the subject. If you can't stop the subject from drifting, cold, it does drift, however slowly, and that is endlessly frustrating.

Several glasses are used to make beads, but the most common are soda lime and borosilicate, whose RI's are ca. 1.523 and 1.474. Am trying to find a combo of spheres and liquid for which the spheres in the liquid would be invisible, i.e. matched RI's. This for imaging sub mm delicate museum...

P.S. Nafion beads are a bit too expensive for this application, but would like the beads to be wettable by an ethanol-water solution. Teflon AF seems not to be wettable...CYTOP might work?

Hello, Am new to this board. Looking for a source for small (~0.200mm), optically clear plastic beads with a refractive index ca. 1.36, which I assume would probably be a fluoropolymer. For example, Norton FEP would be OK, but seems to be supplied only as powder or film? Jonathan