gullygossner wrote:I'd be curious if his epiphany may have came out of a change of philosophy when it comes to roasting based on a BT profile vs an ET profile. I tripped across a post a while back suggesting profiling based only on ET and have been meaning to give it a try as the theory seems fundamentally stable. It's just been hard to give up the BT profile idea as that is what I have focused on for much of my roasting to this.

Timing first crack heat reduction

I wonder a similar thing.

That is a really great post by Jim, simplifies the roasting process perfectly, should be sticky at top of roasting forum.

What I have found recently is that keeping ET or MET steady after yellow to at least the end of first crack is imperative to maximise sweetness, inherent fruit acids and minimize baked defects.

The funny thing is that if my batch size, air flow and burner are correctly balanced a declining BT ROR is a naturally occurring by product.

Sometimes, it may not be perfectly linear but this does not affect the cup as long as ET/MET was kept rock solid, for my system its tasting like 480 - 485F or 248 - 252C is the sweet spot.

If I want a slightly longer or shorter roast im better off keeping everything the same and just tweaking the charge weight.

OldmatefromOZ wrote:I wonder a similar thing.

That is a really great post by Jim, simplifies the roasting process perfectly, should be sticky at top of roasting forum.

What I have found recently is that keeping ET or MET steady after yellow to at least the end of first crack is imperative to maximise sweetness, inherent fruit acids and minimize baked defects.

The funny thing is that if my batch size, air flow and burner are correctly balanced a declining BT ROR is a naturally occurring by product.

Sometimes, it may not be perfectly linear but this does not affect the cup as long as ET/MET was kept rock solid, for my system its tasting like 480 - 485F or 248 - 252C is the sweet spot.

If I want a slightly longer or shorter roast im better off keeping everything the same and just tweaking the charge weight.

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.

On my roaster, I have to reduce MET about 90 seconds before 1C to keep RoR from soaring in 1C. If I reduce it at DE, much earlier, then it's likely to crash or flatline well before 1C. Even if it's possible to find a MET that can be held steady after DE, there's undoubtedly going to be an interaction with charge temp and any MET adjustments before DE. Sounds like it could take a lot of roasts to figure it out for a given bean.

Yes, for me it is similar. I am try to maintain a declining RoR WITHOUT ramps or flattening in the RoR from resulting moisture release from the beans pre-FC. This means at a certain point I would have to drop gas sometime before FC (for me that's like a minute normally) so that deltaBT won't flatten OR ramp then dive; taking the coffee with it into a baked oblivion. Is it even possible to have a consistent MET temp after DE and NOT have your RoR flatline or skyrocket before FC? I'm not optimistic....

Hello:

OldmatefromOZ wrote: ... a really great post by Jim, simplifies the roasting process perfectly, should be sticky at top of roasting forum.

Indeed ...

Ever since I first read it (years after it was posted) I stopped juggling variables and started roasting with just the ET in sight, going into FC right below ~ 250°C.

Striving to achieve that goal every time slowly but steadily helped me better understand how my drum roaster behaves/reacts to gas settings as well as environmental conditions which, with only one variable to keep in check, allowed me to achieve more consistent roasts.

Not perfect, not even among the best but improving constantly.

Yet another sticky (methinks closely related) should be this article in the Coffee-Tech Engineering blog.

coffee-tech blog wrote: Roasting can only truly occur within a narrow heat range, before we start charring the beans. Hitting that sweet spot results in a full-bodied, sophisticated aromatic profile. The best way to get there is through a complex fusion of heat conduction and thermal radiation using the least amount of air possible.

Given the right thermodynamic system, a good coffee-roasting machine can deliver heat through contact - metal surface onto bean surface - without using hot air blasts or gadgetry. Once consistency is maintained and side effects are under control, one can truly reap the reward - a harvest of heavenly flavors.

* underlining is mine.

Cheers,

CIV

edpiep wrote:Yes, for me it is similar. I am try to maintain a declining RoR WITHOUT ramps or flattening in the RoR from resulting moisture release from the beans pre-FC. This means at a certain point I would have to drop gas sometime before FC (for me that's like a minute normally) so that deltaBT won't flatten OR ramp then dive; taking the coffee with it into a baked oblivion. Is it even possible to have a consistent MET temp after DE and NOT have your RoR flatline or skyrocket before FC? I'm not optimistic....

So to clarify the point on "maintaining a steady MET" after DE; it seems based on the shared past posts that there is more a "range" of 450-480F that one should stay in after DE and not a specific temp to maintain (say 475F +/- 1º) correct?

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.

This is from Anne Cooper roasting class, good visual example of the basic theory.

Does "Max. RoR" mean something different than I thought it meant?

That red BT line doesn't look like what I'd expect if the Max RoR X is actually where it's marked. The RoR is the slope of the BT curve, isn't it? So if the RoR is constant I expect the BT curve to be a straight line. If the RoR is increasing I expect a BT curve that is concave upward. If the RoR is decreasing I expect a BT curve that is concave downward.

I'd expect the real maximum RoR (or maybe a local maximum RoR) to be a place where the BT curve transitions from concave up to concave down. But that's not what I see on that graph in the region around that "Max. RoR" X. The BT line is clearly (at least to my eyes) concave downward around that point. So it seems to me that the region of the BT plot around the "Max. RoR" X is consistent with a steadily decreasing RoR.

It looks to me like the real maximum RoR is somewhere between 00:02 and 00:03.

That "Max. RoR" X marks the maximum ET reading, but that's not maximum RoR.

Its not an actual roast, its a pictorial for showing how one might manage the Environment Temperature of a drum roaster. So there is no delta BT ROR for this reason and in the context of this graph / discussion, that is infact the Max ror for the environment temp profile.