wax is not very heat conductive at all, which is why thermal pads dont use it to transfer heat. Thermal pads are same as goop except goop uses an oil to contain the particles (ceramic, aluminium, silver, etc) whereas pads contain them in wax - so that it can be solid and not drip off the heatsink it's stuck to. Thermal pads melt ("phase change") to adapt to the heatsink base & cpu top; but its the particles within that do the heat-transfer, not the wax. Thermal pads are more reminiscent of chewing gum than a candle, partly because no parrafin and mostly because theyre mostly made from the same stuff goop oil is holding. pads are less effective than goop because some wax etc gets in the way; and because a lot of pads are very cheap stuff (notice some OEM goop is pretty crap too); plus the oil is a bit better interface anyway.