Transparency of molten substances?

[Xcellerator]

Hi all,

I was at some event last week and we had tea candles on each table. At one point in the evening, I noticed that the wax in one of the candles had gone entirely molten, and was also completely transparent. The wax was originally opaque.
Now, I understand how transparency works, it's when photons cannot easily excite any of the electrons in orbit around a nucleus (say, Carbon Diamond for example) and if they can excite some of the electrons, then the photons get absorbed and do not pass through the substance (Carbon Graphite). Now logic would dictate that in a liquid, there are far more free electrons than in a solid? And come to think of it, this also applies to several other elements (water), when the liquid state is transparent and the solid state is opaque.

Could anyone explain to me what is going?

 

[M Quack]

For this particular example you are not thinking about the right lines.

Note that for example polished glass is transparent, but etched glass is opaque. The electronic properties of the two are the same. The difference is that etched glass is rough, and light gets scattered into many different directions.

Another good example is snow (opaque) and solid ice (especially if the water is clean and had been boiled before freezing).

When wax hardens, microscopic inhomogeneities form that scatter light. I don't know what type of inhomogeneity exactly, but it is probably related to the fact that most waxes are a mixture of polymer chains of different length.

http://en.wikipedia.org/wiki/Light_scattering