Solar Tech 2kg Roaster confusion! Not consistent roasts!

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Eugenie
Posts: 1
Joined: 7 years ago

#1: Post by Eugenie »

Hi all, I have been roasting with a solar tech roaster for about a year now. I struggle to get a consistent roast. I use a charge temperature of 155 degrees Celsius which he suggested is perfect for all roasts. (At the moment I have Colombia, Brazil, Tanzania, Guatemala and Uganda). The more I read though the more I feel inclined to change the charge temperature to at least 165. Do you think this should make a difference?
I am also wondering about how the higher charge temperature will influence roasting time; development of the coffee bean, top temperature and turning point temperature. My machine is not so easy to manipulate as it has a build-in thing that takes it automatically through all the phases of roasting.
I struggle to get a consistent roast...eg I would roast 2 batches of Colombia with same charge temperature and same preset temperature but top temperature or turning point temperature might differ. The batches even look different sometimes. Or I would roast a Brazil today and a week later use exactly the same settings but the roast comes out different. This make me very unsure of how the coffee would taste and I also do not have confidence in my product. So sorry for the long post but I really need to sort out this problem. No one here actually knows why I struggle...THANKS!

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millcityroasters
Posts: 253
Joined: 9 years ago

#2: Post by millcityroasters »

155C is not ideal for all roasts. You'll have to monitor your green/yellow transition and find the charge temp that gets you there in around 5-6 minutes.

The Solar is usually pretty consistent. I'm guessing either your electrical voltage is fluctuating or your chaff collector and or exhaust system is changing the airflow or the roast.

Séb
Posts: 363
Joined: 10 years ago

#3: Post by Séb »

I agree with Steve. What i really appreciate the most of my Solar roaster is the consistency between batch to batch. A voltage fluctuation would effectively affect your consistency so be sure you have stable voltage first.

Now, the charging temp recommendation of 155 is only that... a starting point recommended to begin with". With a higher voltage (240+V) you will have to decrease thoses settings. The machine is calibrated for 230V. Here i have almost 250V so i needed to decrease my settings compare to what is suggested in the manual. So for sure you can and should play with the charging temp, end temp and if needed you can also compensate with the charging load. If you increase the charge temp by a significant number, it will reduce slightly the drying phase and will also slightly decrease the total roast time. For softer beans like Brazil i use a lower charging temp but for high density SHG beans i will increase the charge temp. But in my case, if i use the exact same load charge, same beans (mean from the same bag) and with the same charging and end temp setting i will get very consistent results. Be sure to keep your green beans also at the same stable temp and humidity or it will affect the consistency.

Also, did you clean the exhaust tubing and cyclone since you have the roaster? I clean mine every maybe 75 roast cycles. An overnight soak in Simple Green, then i use the pressure washer machine to remove everything left and let it dry, then it is ready to go.

summer
Posts: 183
Joined: 12 years ago

#4: Post by summer »

Another thing is that the first roast may be slightly different from the following roasts, due to the roasters chimney and frontplate is not fully up to temp until after the first roast.

edtbjon
Posts: 251
Joined: 9 years ago

#5: Post by edtbjon »

One thing that the OP (Eugene) doesn't say anything about is how and for how long he pre-heats the roaster. If the preheating isn't consistent from session to session, the first roast for the day (and possibly the only roast for the day...) can be just about anything. The energy that one time goes into the beans can the next time (partly) go to heating up the roaster, exhaust or whatever...
I usually heat up my very small Huky for about half an hour, getting at least a decent platform to start my roasting session from. A Solar, weighing in at some 15 times more than the Huky needs quite some time just soaking up heat before becoming a in-tune roasting instrument.

Séb
Posts: 363
Joined: 10 years ago

#6: Post by Séb replying to edtbjon »

On the Solar roaster you enter a charging temp, the roaster will start to heat and when it reach this temp it beep and you drop your beans. The OP said he use 155 as his charging temp for all batch. So he start with the same temp inside of the drum for all his batch. But even if it's the same temp at the probe level, i agree that the body of the roaster, the exhaust, etc are not all as much warmed as with 2nd+ roasts. So this might be possible. He could just do a blind short cycle without any beans to pre-heat even better the roaster, i do that when i have a special bean to start up with. Otherwise i always start roasting with a low density bean like a brazilian and will also compensate the charge temp on my first cycle by increasing it by 10 degree.

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sversimo
Posts: 218
Joined: 13 years ago

#7: Post by sversimo »

Heating it up higher before your first roast should help, but you might wanna try recording -everything- you do during a roast and see if there is anything you have missed.