neutral density polymer beads - latex or ???

I'm looking for some neutral density polymer beads/microspheres for use in visualizing current flows in water. They don't need to be exactly neutral density, as long as they stay suspended for 5-10 min or so, that will work for our purposes. They should be large enough to see individual particles (~10-100 um or so). I have come across references to using latex microspheres for this, but the only suppliers of latex microspheres I have been able to find sell either very small spheres (< 1um), or highly monodisperse spheres, and both are very expensive.

Does anyone know where I can get relatively inexpensive latex (or other near-neutral density polymer) beads of ~10-100 um? Can contain a range of sizes, and need not be perfect spheres.

Dr. Forrest Stevens Washington State University snipped-for-privacy@pullman.com

Sorry it took so long to post an answer.

Polysciences

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has a huge selection of polystyrene microspheres (s.g. = 1.05, nearly neutral) ranging from 0.05 micron to 600 micron. I can't tell you about pricing. These type of beads are used for calibration purposes, and are generally prepared by anionic polymerization in order to control the size so tightly.

If this option is too pricey, you may want to contact Dow or another PS producer directly. You could just get a 50 lb bag of GPPS (general purpose PS) and try to use a grinder/series of sifters to get what you need.

Another option would be to talk to a local plastics processor/compounder who works with polystyrene.

One last thought would be to contact Aveka

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They may have what you want or could probably help with the grinding/seiving that I suggested. There are probably other more-local shops that could do the grinding as well.

(Where are you in the WSU organization? I couldn't find your department easily.)

John