I have done minimal roasting on an IR3, think the smallest batch size I roasted where I felt temp readings were accurate was 3 lbs. At three pounds the bean temp probe seemed to be completely covered by beans making it the smallest batch I would feel comfortable with the temp reading.
Part of roaster design, and probably more so on Diedrich's, is utilizing the retained heat of the thermal mass in the drum for profiling. At 3 lbs, the charge temp had to be considerably lower than at full batch, although I don't remember exactly what temp that was.
I can't imagine that roasting 1 lb samples would be realistic on a IR3, but perhaps with practice you can dial it in.
I am roasting on an IR-3 and have found that, like Keith mentioned, that 3 lbs. is really the break point where you get good, accurate readings from your temp probe. I currently roast most of my stuff at 4 lbs. output (4lbs, 12.8 oz.) I get a great roast at this size batch.I am not hooked up to an exhaust system, so load temps may vary as well as gas, but I'm loading at 380F with a turn around at 1:30 at about 230F and a first crack at 365/9:00 min.
The guy who owned it said that crack happened anywhere from 365-380. I've also found that, as a guy roasting fairly light, that drop temps were a bit lower than is typical. But i'll let you decide for yourself what you want to do.
I hope all is going well for you.
One of the great things about Diedrichs is their constancy with varied batch sizes. I don't have too much more to add. Just wanted to say hi;)
Like D. Smith stated, the primary difference with small batches is the reading from your temperature probe. Once you're comfortable with the nuances and what happens while roasting full batches, roasting a 200g 'sample' batch is very reasonable. With a small batch, you're just having to pay more attention to all of the other changes during the roast and realize that the bean temp is not as accurate.
With our IR-12, I've had good success roasting 1lb batches for sample/testing purposes. Granted, I do try to do 2 or 3 lb batches for sampling, but have had reasonable success with smaller than 1 lb also. I start with a lower charge temp, watch for the same milestones and draw out the total batch time to close to the same as a full batch.
Ghost Town Coffee Roasters
No retail yet, but it's been on the mind.
Timothy Pellizzer said:
Thanks for all the helpful comments. Chad you changed the name of your operation. Did you add a retail store? Hope to see you soon.
Let me know if I can be of help if you go that direction