Internal scorching and tipping.

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
saveme45
Posts: 8
Joined: 2 years ago

#1: Post by saveme45 »

Greetings to all!
I am a beginner roaster. I'm roasting on a Yoshan BY-1 roaster. Each roast is burnt. Basically i get tipping on any beans. I followed the tips for decreasing burner energy, increasing drum speed, decreasing / increasing airflow. The grain is darker on the inside than on the outside. This defect is more pronounced on the grain of natural processing. I tried roasting for 15 minutes, stretching the drying phase to 7 minutes. I tried quick roast for 8 minutes and the problem persists. Maybe someone owns this machine and can give advice on how to avoid a defect on it? The supplier does not reply to emails. I'm already try to use heat shield between burners and drum, it doesnt work :( now i increase distance from burner to drum, i'll try to roast this week.

OldmatefromOZ
Posts: 316
Joined: 10 years ago

#2: Post by OldmatefromOZ »

Assume by burners its gas roaster?

What is the actual internal diameter of the drum? As its a good starting point to set drum rpm by. Going by pictures alone it looks like a longer style drum which work better at whatever the highest recommended rpm is for its diameter in my experience.

What batch sizes have you tried?
The burners might be quite powerful possibly even overpowered for the size of the drums roasting environment hot box?
So small batches become very hard to control and are overwhelmed by too much heat sealing in the juices, basically the seeds just take on far too much heat too quickly.


Its possible that the roaster might be optimal using an 1kg charge or possibly 1.2kg with highest possible drum speed
( im guessing by looks 76 to 78 rpm might be good for the long drum)

Set your airflow using the cigarette lighter trick on trier hole 2 to 3 mins into a 1kg green roast and leave it alone or only make one small increase at dry end / beans yellow.

Observe what time your max burner setting gets 1kg green to first crack and let it go to 2nd crack then turn it off / cool quickly.
This will give you a better idea of how powerful burner is.

saveme45 (original poster)
Posts: 8
Joined: 2 years ago

#3: Post by saveme45 (original poster) »

Thanks a lot!
Drum diameter 21cm. Length 24. I have tried to fry batches of 600 to 1200 grams. I get tipping and internal burning anyway. Using the traer method, my sufficient airflow is 3.5. I used the drum revolutions from 30 to 60, but my 60 revolutions on the dial are equal to 78 real revolutions.
When I increase drum speed around 60-70 my ET drops lower BT. When my drum speed around 30-35 RPM(real 42-45), my ET higher than BT...

Rickpatbrown
Posts: 460
Joined: 5 years ago

#4: Post by Rickpatbrown »


OldmatefromOZ
Posts: 316
Joined: 10 years ago

#5: Post by OldmatefromOZ »

ET probe looks like its up near hopper gate?
This is quite far away from the action and rarely useful on a small drum.

You would be better off running an insulated bead k type thermocouple through one of the bottom bolts which hold exhaust / hopper manifold on face plate.
Position so it has no bean contact just reading the hot air coming straight off the beans.

Given the drum dimensions I would keep it at 78 rpm actual.

A basic approach to shoot for with suggested new probe.
Charge around 250C
Steady rise to peak ET around 7 min.
Hold steady as possible, may need slight dip pre first crack then let it go until first crack is done and see what that yields?

Airflow, find a neutral flame at trier port then increase fan gradually so that it just starts pulling in.

User avatar
Almico
Posts: 3612
Joined: 10 years ago

#6: Post by Almico »

Most roaster manufacturers know surprisingly little about roasting coffee.

The first thing I would do is check your temperature probes. The mfg probes on my 5kg roast are so bad. They are not only in poor locations, but they don't come close to being responsive enough to give accurate readings. Here is a pic of the temperatures I'm getting from Artisan and you can see in the background what the stock probes are saying. If I was going by the stock probes I couldn't help but burn every batch. I bought this roaster used and I'm quite sure the previous owner had more than his share of fires in this roaster.

Pull your probes. If they are the 5-6mm diameter ones they are probably useless. Replace them with 3mm probes.


saveme45 (original poster)
Posts: 8
Joined: 2 years ago

#7: Post by saveme45 (original poster) »

Thank you so much for your recommendations!
My probes are 5mm. Today I pay for new probes 3mm. I'll get it in the middle of January I hope. I'll setup it to correct places and will check difference of temperatures.

pcofftenyo
Supporter ♡
Posts: 354
Joined: 7 years ago

#8: Post by pcofftenyo replying to saveme45 »

The below link discusses all manner of roasting defects.
Internal scorching/tipping is found early on in the roast. "Over-roasting" is too long after 1C. IMO, 2:30 development (1C to drop) in a 10:45 roast will likely lead to unpleasant flavors.

Does your coffee have oil on it immediately after roasting? In 2 days? In a week?

What is the temp change from the start of 1C to drop?

saveme45 (original poster)
Posts: 8
Joined: 2 years ago

#9: Post by saveme45 (original poster) »

I have no oil on beans. After FC temperature grows up to 7-10 degrees, not too much.

saveme45 (original poster)
Posts: 8
Joined: 2 years ago

#10: Post by saveme45 (original poster) »

Hi all!
I received new thermocouples and installed them in new locations. ET sensor in the upper left corner of the drum. the BT sensor is closer to the beans.
Now my turning point is about 85 degrees Celsius with a load of 190 degrees Celsius with 700 grams of beans. Before it was around 110-115 degrees.

yesterday it was not possible to write a log to Artisan.
my charge temp was 190 degrees, TP 85 degrees at 0:55. ET is 150 degrees. There was no gas at first minute and no airflow to 5 minutes.
I'm worried about the high ET temperature before the first crack. at 190 BT there were 265 ETs. is it very hot?

Post Reply