In a big roaster (and most small ones) the beans in the drum go round and round, for 12 to 14 minutes. Then they're dumped into the cooling tray and stirred for another 5-10 minutes, followed by a trip through the de-stoner (sort of giant cyclonic vacuum cleaner) before binning or bagging. Pre-mixed roasted blends are about as well mixed as it would be possible to get.

Alan

If you look at tumbling in a roaster, stirring in a cooler, and destoning in a cyclone; only tumbling in a roaster would keep a non homogenous blend homogenized. A cyclone will have heavier particles settle before lighter. Horizontal stirring during cooling of a bean container will be the reverse with smaller particles settling to the bottom. Only the tumble of the roaster would evenly mix different sized particles. In blends with dramatically different sized beans, I still see potential for uneven distribution.

Blends of whole bean coffee, either blended green or roasted, will separate in the transportation-delivery process. How much and the impact on individual shots is always the question.

yakster wrote:From Sweet Maria's website regarding their Liquid Amber blend:

Green liquid amber is kind of a worst case since those monsooned beans are swollen and huge. Once you roast it the size is more uniform, since the non monsooned beans expand and the monsooned beans pretty much stay the same.

I have had to stir the green liquid amber to try to reverse settling from shipping, but I've never had it be an obvious issue after roasting.

I think it's important to remember in these sort of discussions, REAL WORLD, REAL WORLD and REAL WORLD. In the real world of coffee blends most beans are about the same size, weight and density, and the outliers like Maui Mocha or Maragogype are rarely if ever used in blends. I have never seen any sort of layering happen in regular blends in 30 years in the trade. That's not to say I couldn't design a blend that would increase the probability that it might happen!

Alan