I would imagine that traditional pitch/tar (being a big bag of long molecules) is itself already a non-Newtonian fluid (is temporarily harder under impact). Se

I would imagine that traditional pitch/tar (being a big bag of long molecules) is itself already a non-Newtonian fluid (is temporarily harder under impact). See http://en.wikipedia.org/wiki/Pitch_drop_experiment http://en.wikipedia.org/wiki/Pitch_drop_experiment for why you can consider pitch a very viscous fluid.