During the 1900 K period, the NP lost ~33% of its mass, and the slope of M vs. time was roughly constant, but with small fluctuations. Fig. reports the mass loss rates (Rbase = Rbackground + Rsublimation) extracted by a series of linear fits to time periods where the slopes were constant, normalized to the surface area of a spherical NP with the mass observed at each time point. The point labeled "1300 K" was the mass loss rate measured just before TNP was increased to 1900 K, and at that TNP, Rbase ≈ Rbackground. At 1900 K Rbase was more than two orders of magnitude higher, with the increase attributed to sublimation. The background-subtracted Rsublimation was ~1.4 x 10 -1 Da/sec/nm 2 at the beginning of the 1900 K period, gradually dropping to ~8 x 10 -2 Da/sec/nm 2 by the end, again suggesting that the NP continued to evolve slowly to become more Si-rich as it sublimed at 1900 K. While 1900 K is only ~95% of the silica Tmelt, diffusion within the NP would presumably have been reasonably fast compared to the hours-long experiment.