Hi everyone,
After 4-attemps to control the post FC crash on these Burundi Monge Murambi Hill beans I'm out of tricks and welcome advice. The first plot shows what the beans do with no gas adjustments through FC. This is my reference from which I like to make adjustments. There doesn't seem to be much pre FC rise but seconds after FC there is a massive crash that a burst of full 3.4Kpa won't flatten. A further complication is after the crash the RoR wants to climb so whatever adjustment made for crash correction must be quickly negated to comp the flick. I have reasonable luck on other bean varieties dropping gas before FC and raising it a bit after FC then tailing gas off till drop but these Burundi beans are just wily.
First Graph # 297 Un-comped. Fan level indicated in "WC on Temperature axis.


Second graph, gas increase 40-sec before FC. One could extend the pulse of 3.4Kpa but timing would be critical to cut back heat before the flick starts. The beans SMELL sweet but the graph looks unpromising and is the stuff of Rao's nightmares. I'll sample #281 in a few days and report.



Comments please.

John,

At 7 min each profile starts to flatline. What if you took heat out then. Slow adjustments down. Maybe add some heat back in once you get it continuing down at 7.

Michael,

You raise a good point. I will try taking heat out before 7-min and see if the crash is easier to control. The flat line at 7 definitely needs fixing. Are there opinions on a preferred RoR level at FC? This one is about 13 F/Min and when I take heat out to fix the flat-lining, RoR will be lower. Perhaps this is irrelevant...
Also, did I read in one of the posts that taking moisture out with high fan settings early on lessens FC crash?
I have high hopes for this Burundi bean. The present roasts are out-gassing a fruity sweet cherry smell. I've got to try #281 in the morning.

John remind us is 3.2 your max gas? You can try some things to keep your ROR closer to 15 at FCs. Go higher at start if you can. Or go to 3.0 at soak end and max at ROR peak. May not work but things to try.

Gas (house propane) max is 3.4Kpa. The gas tech said I could go a little higher on the house line but household appliances would need a regulator so I stayed with 3.4K at the roaster.
Michael, I tried maxing out the gas to 3.4K after a 60-sec soak at 0.8K. I also LOWERED the charge temp to 392 (PID) from 403 on previous runs, trying a bigger delta from the TP. However RoR max is no higher at start, but hung in there higher than before. An improvement overall.

This time I feathered the gas drop from max down to 2.2K and could have gone even lower to fix the flat-line at 7-min. A BUMP up to full 3.4K reduced the FC crash but didn't tame it. Do I need more air flow to dry the beans more? I've highlighted today's gas settings in green. Sorry it looks like chicken scratch.
I see others are measuring density and moisture levels of beans. Is this African bean overly wet?

John, ok that's a lesson. Still think you have to go lower on gas before the crash. You can try more air too, but you are flatlining still before the crash. You are NOT alone though. I have a similar problem with my sweet Guat.

Guatemala Xinabajul Marca Roja - Roasting Discussion

I am not going to try to adjust it until my new probes are in after Wednesday. In a way it looks like yours and I see my gas was down near 2.2 or 2 and may need to try much lower with an adjustment back up at some point. I also have Scott Rao's book coming so see if he has a useful suggestion.


On Artisan if you are so inclined you can make some changes so you don't have to write on your curves:
Lower the gas readings on your curves - for your buttons, use a lower value and have the description field reported by using Step+ or Combo and using an description. Also you can relabel Power to Gas. New improvements with even greater options coming. Happy to work with you on this.

Michael, Later today I'll drop the heat even lower to address the flat-lining. There is so much weird stuff going on at FC physically and I wonder if you can go into FC too-hot.
My Rao book is also on order and look forward to reading it. One more 12-oz roast of the Burundi left, then it's on to a 5# sack of said Guat Xinabajul Roja. I've been reading the post on it and just got some in.

I'll try getting Gas values to print in Artisan as above and installing an alarm 30s or so after I call FC, or from the phases table somehow. What do you recommend there? It may be useful to get a heads up for shaping the bump. But first it's back to fixing the kitchen faucet...

Rao's gas dip technique says to cut gas by 50% for 20s about 40-60s before the crash, then revert it to where it was and don't touch it until 12% DTR at which point you cut in half, then half again, then half again to finish your roast.

I also think you're coming into crack too aggressively.

Chris,
Thanks for the tips. It's surprising how rapidly one needs to shut down the heat after 10% DT or so. When using the 12% metric, what is your target range for first crack, 8-9 min?
J

I would try the following changes: reduce soak to 30s and try to get a combination of a maximum fan and gas settings that will get you through the dry under 5 min. The point is to avoid a change in gas setting around FC but you should have some fan headroom, less airflow in practice, that would allow you to better control the crash.