Dear Authors,

I am happy to accept your manuscript for publication in Atmospheric Chemistry and Physics. Since you are reporting freezing rates, I believe it would be fair to mention the caveats regarding uncertainty in particle surface areas as discussed in Hartmann et al. (2016) and Alpert and Knopf (2016). This is independent of applied data set. Despite same weight percent a few small particles will have a much larger surface area than a single larger one acting as INPs. This surface area will likely also vary from droplet to droplet (in large droplets or in emulsions experiments, etc.).
I just suggest to mention this in one sentence, maybe, in the conclusions so the reader is aware of this issue and that it is being discussed. I don't think any more changes on the manuscript are necessary.

With best regards,

Daniel Knopf


References:
Hartmann, S., Wex, H., Clauss, T., Augustin-Bauditz, S., Niedermeier, D., Rösch, M., and Stratmann, F.: Immersion freezing of kaolinite: Scaling with particle surface area, J. Atmos. Sci., 73, 263–278, 2016.

Alpert , P. A. and Knopf, D. A., Analysis of isothermal and cooling-rate-dependent immersion
freezing by a unifying stochastic ice nucleation model. Atmos. Chem. Phys., 16, 2083–2107, 2016.