Hello again Georg,

>Superheating is achieved more easy by microwaves for a reason not mentioned yet: If You heat from outside, by a flame or a electric heating plate, You always have a thin boundary layer with a temperature higher that the bulk in Your pot.<

Here I am happy to agree. I suspect that the reason no one mentioned it, is the fact that we all regarded it as a given.

>If You heat some viscous lqwuid from outside, some other phenomenon takes place: film evaporation and "burning" of the viscous mass... etc<

Yes Georg, but why on earth should anyone mix that up with "not easily superheated". It seems to me that high viscosity interferes with convection. To hamper convection seems to me likely to favour the formation of hotspots. Hotspots seem to me extremely likely to lead to symmetry breaking, with the production of free vapour and the initiation of boiling, at least locally. Are we at cross purposes?

Go well,

Jon

Hi Georg,

I suppose i should have done this long ago, but I went and did some WWW surfing, since you seem sceptical of my own observations (not to mention arguments). There is no shortage of sites that deal with topics, usually at a technically illiterate level, but there also are some professional-level items as well. Here is one that you will enjoy, I am sure. It is an extract from an abstract:

"It is generally believed that oil samples heat faster in a microwave oven than do water samples of the same mass. For sufficiently large and thich samples this conventional wisdom is indeed correct, but this trend can be far from true in smaller samples. In a commercially-made home microwave oven, we observed that with decreasing sample size the heating rate of a water sample increases much faster than that of an oil sample. At 50 g the heating rate of a water sample is several times greater than that of an oil sample. Additionally, in studies of cylindrical samples in a customized oven having a unidirectional microwave source, the heating rate of water samples smaller than 2.4 cm in radius is greater than that of oil samples and is a strongly oscillatory increasing function of decreasing sample radius. Combining Maxwell's theory of microwave penetration and the heat conduction equation, we show that this previously unreported oscillatory heating behavior results from the added power absorbed by samples due to resonant absorption of microwaves...."

The site is: http://onlinelibrary.wiley.com/doi/10.1002/aic.690400902/abstract

If you have access to the original you might find it entertaining to follow it up.

Other sites of interest in this connection:

http://www.physicsforums.com/showthread.php?t=316981

http://amasci.com/weird/microexp.html

Have fun!

Jon