Coffee Cup Rainbow
If you look into a coffee cup as soon as it is poured, the foam bubbles have an iridescence to them, caused by the natural oils within the beans that have just been released by the grinding process. This is the same oil that coats beans that have been darkly roasted, like espresso beans. The oils, then, are released as the hull fractures during the extended roasting time and covers them.
View Large to really see the colors!
Coffee Cup Rainbow
If you look into a coffee cup as soon as it is poured, the foam bubbles have an iridescence to them, caused by the natural oils within the beans that have just been released by the grinding process. This is the same oil that coats beans that have been darkly roasted, like espresso beans. The oils, then, are released as the hull fractures during the extended roasting time and covers them.
View Large to really see the colors!