edpiep wrote:Are you suggesting then that the MET temp itself should be flatline after yellow until right before you drop if you only roast into FC? In my case this would mean that MET would be "capped" or at it's max temp for 1/2 of the roast until drop.
It's interesting to me this suggestion b/c I have been thinking a higher overall MET temp post DE would allow for maximum energy for development to happen in the least amount of time. SO then it's a matter of finding that MET temp that doesn't scorch or tip the beans but really digs into the bean cores for an efficient FC and ensuing dev time. That's my logic at least, could very well be flawed.
As ususual with roasting it depends...
Im still learning every roast I cup and a lot depends what one is looking for in roasted coffee?
As others have mentioned the roasting system in use will always have its unique properties (temp measurements / placement) so it may need to be different.
The point is that particularly for small home roasters having some kind of MET / ET reading thats reliable and changes to it bring notable differences to a blind cupping is more useful than chasing perfect BT lines.
Big crashes and flicks in BT ROR make coffee taste bad no question, i think more often than not its because of poorly managed roasting environment temperature.
Jims suggestion of a ballpark overall roasting coffee recipe is a good way to get consistent results and establish a base line for your system.
So if you hit start yellow / colour change at say 4:30 then soon after around 6 min the "roast stage"
is starting and MET / ET peaks and from here on you do not want any drastic changes to the roasting environment, so holding it as steady as possible is a good idea.
How that actually works and looks on a measurement profile will depend on how much thermal mass / how big the drum is / charge weight needs to be accounted for?
What ive found on a small gas drum 500g is thats its possible to get any number of nice looking ROR plots where the roast is baked to hell achieving it.
Civ quote is on point, the sweet spot for any given roasting system does seem to be quite narrow.
For very light filter roasts (im no where near mastering) im currently thinking a hot start which takes a little longer for a slightly lower max temp to peak around yellow, then have that decline by 10C by 1 min before first crack starts and hold it steady until to drop. This should result in a fairly smooth decline in ROR.
But if someone wants a darker roasts say around just before second crack starts, then holding the temp steady as possible around 248 - 250 from just after yellow, at least until first crack is just about done and then having it slowly drop to 240ish for a 3 min 5.5C / min finish seems about right for balacing development time while minimizing baking.