  Low ice adhesion surfaces are a promising anti-icing strategy. However,
reported ice adhesion strengths cannot be directly compared between research
groups. This study compares results obtained from testing the ice adhesion
strength on the same surface at two different laboratories, testing two
different types of ice with different ice adhesion test methods at temperatures
of $-10^o$C and $-18^o$C. One laboratory uses the centrifuge adhesion test and
tests precipitation ice and bulk water ice, while the other laboratory uses a
vertical shear test and tests only bulk water ice. The surfaces tested were
bare aluminum and a commercial icephobic coating, with all samples prepared in
the same manner. The results showed comparability in the general trends,
surprisingly, with the greatest differences for bare aluminum surfaces at
temperature $-10^o$C. For bulk water ice, the vertical shear test resulted in
systematically higher ice adhesion strength than the centrifugal adhesion test.
The standard deviation depends on the surface type and seems to scale with the
absolute value of the ice adhesion strength. The experiments capture the
overall trends in which the ice adhesion strength surprisingly decreases from
$-10^o$C to $-18^o$C for aluminum and is almost independent of temperature for
a commercial icephobic coating. In addition, the study captures similar trends
in the effect of ice type on ice adhesion strength as previously reported and
substantiates that ice formation is a key parameter for ice adhesion
mechanisms.
