I have always had a lot of problems with discussion of roast degree. There are so many definitions floating around and many interpretations. Some of that lies in the liberal interpretations that are taken in descriptions.
I have seen fancy color coded color bars, listing actual agtron numbers on the bags, and even creating new roast degrees like 'full flavor'.
There is a problem.
If your roast has a high delta (outside bean color is in stark color contrast with grind samples) vs a very even roast, the same end level of agrton(grind sample) or drop point can mean something entirely different.
Our roasters are kinda special. The three we have are the only ones in North America like them.
Having an airflow where a normal roast that uses 5 of 10 settings, total control of drum RPM through a roast, a small enough batch size to really do some things you couldn't in larger batch sizes but large enough to be consistent, and a wicked patented hybrid drum. The drum is about ~60lbs of ~1" cast iron with some 2000 holes drilled by hand in the side and around the barrel. This allows for some really neat profiles that somewhat defy classic experience and traditional approaches.
We avoid the issues commonly associated with a perforated drum by having the large drum mass and a small ratio of perforations instead of the traditional screen. This also seems to make the roasts more stable since you are depending on the stored heat instead of ambient chamber air. Something that is more of an issue with an air roaster or any roaster that uses convection. You have such a tight control of airflow and still heat can penetrate so quickly that you can literally approach the roast in a solid drum/hot air hybrid profile and get some really unique elements out of the coffees.
Roasting is fairly consistent, keep tabs on the gas gauge, adjust for the ambient temp/humidity and go. Variance depends on humidity but there have not been any grassy or raw roasts produced, I promise. That's why I sign every roast that goes out because we cupped it first.
The point is, I can get to the exact same color or drop temp a myriad of ways. This renders a lot of the normal terminology a bit useless to a consumer. Our goal is to get the consumer into focusing on flavor decisions, not roast or origin buys so we had to come at it differently.
So I came up with a basic method we will use for now. Roast the coffees to the profile that works best. Note the 'degree of roast' by how much origin character vs roast development.
The idea is to use a number, 1 through 6, 1 being the most origin forward, 6 being the most roast development in the prescribed brewing method. Since we neither do a french roast nor a decaf, this works for now.
Style 5 would have a lot of roast development and softened origin characters, sweet deep roast notes would be dveloped. Style 2 would have little to no roast notes and intense origin characters like aroma and acidity would be enhanced.
It's a subtle thing on the bags and it doesn't really affect our overall approach that much but it was the best compromise. We are medium roasters, not dark simply for dark or light for the sake of light. We stay in that medium range and look for balance unless the coffee likes a little roast or a lot less.
By the way, the Kiandu is in the US, will be here soon. One of the first coffees to come out of Kenya vac sealed, should be fun to roast really fresh coffee.
