INSs, we investigated the differential centrifugation washing step alone (Figure Before discussing the results for the washing step, we first discuss the variability of the INS concentrations for unprocessed K-feldspar and Snomax samples. The INS concentrations for K-feldspar, even for the unprocessed samples, fluctuate by up to a factor of 20 from experiment to experiment (Figure and Figure ). This variability is observed between replicates of the same K-feldspar solution performed on different days and between replicates of the same K-feldspar solution performed on the same day. This corresponds to median freezing temperature fluctuations of up to ~2.5 °C. This variability is likely due, at least in part, to inhomogeneity in the K-feldspar suspensions, rather than the uncertainty in our temperature measurements, which is small (±0.25 °C). INS concentrations for unprocessed Snomax samples also fluctuate by up to a factor of 20 from experiment to experiment (Figure and Figure ). This corresponds to median freezing temperature fluctuations of up to ~0.75 °C. This variability is also likely due, at least in part, to inhomogeneity in Snomax suspensions, but may also be influenced by the uncertainty in our temperature measurements (±0.25 °C). The variability for the unprocessed samples is important to keep in mind when analyzing the data below. Information Classification: General sediment effectively during the differential centrifugation process. Our calculations suggest that the centrifugal force and time used during the washing step are sufficient for organic particles with sizes greater than ~0.3 μm and inorganic particles with sizes greater than ~0.08 μm to sediment (See SI, Section S2, Table ). Therefore, if there are K-feldspar and Snomax particles present smaller than 0.08 µm and 0.3 µm, respectively, they may remain in the supernatant.