Silicon tubing was filled with microbubbles (ave diameter 2.5 µm) or microspheres (2.0 µm). The microspheres were diluted to give the same number of particles/ml as in the microbubbles. The black dyed microbubbles are assumed to be the same size and number/ml as the regular microbubbles (this assumption is being checked). Particles were mixed with .75% carboxy methocellulose.

At a concentration of 1%, all types of particles were clearly visible. The microbubbles were more highly backreflective and more attenuating than the microspheres. The black-dyed microbubbles appeared more reflective than the regular microbubbles. However, it was also possible to see deeper into the black-dyed microbubble solution than the regular. This phenomona has been mentioned by other researchers, and is possibly due to a reduction in the amount of multiply scattered light.