View Thread

renatoa wrote:

How high is your pot ?
This will decide the balance of IR versus convection.
The addition of IR changes things significantly... I can give you numbers from my setup only, as a guideline. For a lamp to beans distance of 8 cm.
The same roast that needed 72-75% power levels for 10-11 minutes with screen plate mounted, take 8-9 minute with 65% power with screen removed at all.

Also, different power management cases: with IR you should reduce power as FC approaches, as for a conventional roaster, with convection you can keep power flat from DE to the end.

Koffee Kosmo wrote:

The amount of heat available from the TO is closely related to the overall volume of the roast chamber for best roast results

Greater volume will result in baking not roasting
To small a volume and the roast will burn

So look at my thread for all the details regarding ideal volume

KK

allenb wrote:

Ok, second roast, a nice colombian, didn't turn out so nice. Very flat and underdeveloped in the cup and noticed the usual nice aroma of the beans when transferring to a mason jar after roasting was missing. So, need help with best practice for ET in a turbo oven roaster that uses halogen lamp for heat source. ET sensor is 2" above bean mass, 2" out from stainless pot wall

Here's my ET/BT results from the roast after preheat at 150C for 3 min.

min 1 ET 137 BT 88
min 2 ET 149 BT 114
min 3 ET 174 BT 134
min 4 ET 198 BT 150
min 5 ET 218 BT 167
min 6 ET 232 BT 182
min 7 ET 245 BT 195
min 8 ET 246 BT 206
min 9 ET 246 BT 212
min 10 ET 246 BT 216
min 10:10 ET 246 BT 218 End of Roast. Level of roast = medium roast.

Koffee Kosmo wrote:

What was the green bean weight ?

I normally pre heat at full heat limit of the TO

And lastly - we don’t talk as much about another, but most important part of the roast
That is the degas period
Depending on the bean origin - The degas period ranges from 5 days to 14 days before the roast can develop its flavour

KK

renatoa wrote:

How was the second roast different from the first (excellent cupping), as timing and power levels?

Are you reducing power when browning starts ?

Attached are two roasts of the same Eth coffee, with or without lamp shield plate attached.
You can notice that the IR version has 5 C lower ET, and needs about 5% power reduction in the Maillard phase, even if both roasts top power in the dry end is close, in the 76-77% ballpark.
~~~

allenb wrote:



I'm doing all of my testing at 1 lb charge. I can try higher temp preheat but I find the roaster more than capable of moving the beans through any fast profile desired, in fact, much faster than desired if so programed and this is with a much lower preheat temp.

As you and I have been roasting for literally decades, no need to discuss optimum post roast wait. Most of my roasts cup very nicely within hours of a roast and do not change that much each day after roasting.

What do you find is a minimum roast time that still gives you optimal results?

renatoa wrote:

Indeed, volume is a key factor, especially for a majoritar convective roasting, where heat losses are significant, and walls are mandatory to be insulated.
And also the agitation is critical, I got uneven roasts easily until the paddle was been finely tuned for the available RPM.

For IR roasting, because energy hits the beans directly, insulation is less critical, and roast is much more uniform, if the coffee bed is not higher than 3-4 layers, which equates to one pound greens in a 23 cm dia roasting area.
When roasting using IR mainly convection role is more to ensure an uniform ambient, hot air is a lot less hotter than in case of convection roasting, at least 10 C degrees lower, that can be seen on chaff color, honey gold, instead dark brown.

I normally do 1 kg green now
Roasting for drinking
Minimum roast time is 9 min to first crack
However I much prefer longer at around 12 min to first crack

allenb wrote:



My preferred time to first crack is closer to 10 min on my drum roaster so we've got similar roast stage times. I will experiment with these times on my next testing runs.

Is your heat transfer primarily radiant with convection coming in 2nd?