Researchers have now measured elastic behavior in water (free access until ~ September 14, 2012 with registration). I found the report fascinating for a number of reasons. First, the tests were completed on macroscopic samples. The published data was for 0.125 mm thick layers of water, but the researchers had gone to samples as thick as 0.5 mm. Secondly, the results were just what was expected. For instance, here is a strain sweep:
"It is interesting to note that the evolution from the low strain amplitude sinusoidal wave to the large strain amplitude sinusoidal-like wave does not correspond to a simple shift of the phase but to a strong modification of the signal."More research is needed! And quickly please![*]
But lastly, the coolest part of this research is that is was done not with an ultrasophisticated instrument build just for this purpose but using a rather mundane and ordinary rheometer - an ARES2! Yes, it was modified slightly - the parallel plates were made from nonporous alumina (40 mm diameter of course), and the input and output signals were monitored by a 7-digit voltmeter rather than with the standard hardware/software, but that's it. Nothing more was done. This testing is something that pretty much any rheology lab in the world could measure. It's that simple.
[*] There is one plot in the article that was made at an intermediate strain, but to discuss it would require getting too involved in the rheological details, and besides, that one plot is only one place along the transition from the low to high strains. It's not enough. I still want to see the whole evolution from small to large strains and there are a lot of gaps to fill in.