(A) Schematic diagram of the radial flow chamber. The chamber was made of a Plexiglas housing with 2 optically flat glass discs, one 75 mm and the other 50 mm in diameter. The 50-mm glass disc was permanently cemented to the housing and bored with a 0.125-inch diameter inlet port through its center. The fluid flows in through the center of the cemented disc and flows out radially between 2 discs with a gap of 300 μm. (B) Schematic diagram of the scanned fields during experiments. A region containing 8 fields by 4 fields of the disc was scanned at increments proportional to the shear rate.