weight. Sample volumes were about 1 cm$^3$. Knowing the density of each species permits calculation of the final composition.

The main uncertainty in sample composition comes from a systematic uncertainty in the calibrated volume fraction of the colloid stock. This is because the volume fractions of coexisting fluid and crystal phases for slightly polydisperse hard-spheres are slightly different from those in a monodisperse colloid, but the exact values are uncertain [@polyFractionateBolhuis; @polyFractionateBartlett]. However, all samples were prepared from the same stocks of colloids and polymer solutions, or stocks calibrated against each other. Some samples were also derived from others in a controlled way (see next paragraph). Therefore despite some systematic uncertainties in the estimation of absolute volume fractions due to polydispersity, the uncertainties in sample compositions relative to each other were mostly from random errors in weighing. These uncertainties are below a percent in the worst case and are insignificant in this work.

Samples were tumbled for prolonged periods of time to ensure proper mixing of the components. After homogenizing, a small amount of each sample was transferred to 3 mm-inner diameter glass tubes and sealed for light scattering experiments. The rest of the sample was then left undisturbed for 