Iowa_Boy wrote:Wanted to better understand what the ROR curves look like on the provided profiles.
Using the Guatemala Blue Ayarza beans and provided profile, I was able to connect to Artisan via a Perfect Prime 3 mm K type thermocouple and Phidgets.
Used Ikawa recommended Medium-Dark++ profile.

Thoughts on the first 2-3 minutes of this curve?

image

Ikawa's recipe does that quick initial temperature spike thing, which I imagine wreaks a lot of thermal havoc early in the program. So perhaps it's taking 2-3 minutes for the system to calm down, given all the sensor delay times.

What is the "thermocouple and Phidgets" thingy you mentioned - is that something I can buy or build?

I suspect that it is very difficult to measure bean temperature in an air, excuse me, fluid bed roaster. In a drum, the heat goes direct to the beans, and the hot beans and the air heated by the beans touch the sensor. In the Ikawa, hotter air is heating the beans and the sensor simultaneously.

Disclaimer: I'm a mathematician. That's worse than a physicist and much worse than an engineer for answering this question. Doesn't stop us, sadly.

Some additional factors to noodle on:

The thermal conductivity and diffusivity of a roasting coffee bean is kinda awful (similar to chalk) making the beans the weakest link in the heat transfer process. Air can transfer heat better than the bean itself, so it may not matter so much if a steel drum is making direct contact with the beans.

The heat capacity of air is very poor (about the same as the coffee bean) - but that also means air temperature can turn on a dime, and cranking up the airflow can mitigate the heat transfer. This approach is used for testing semiconductors - called thermal forcing systems, which are refrigerator-sized versions of the Ikawa roaster (sorta). It seems that air roasters like the Ikawa are being programmed to act like drum roasters, but they have the potential to do much more.

An IR sensor may produce the most accurate measurement of the bean's heat, but a 230 degree-C roasting chamber is a showstopper for most (all?) semiconductor technologies - or has someone figured out how to do it? Glass blocks IR radiation, so the sensor needs to have a direct line of sight.

My testing so far seems to infer the bean lags the chamber temperature by less than a minute, after which the thermocouple readings are identical with or without beans present. If the beans were warmer or cooler, I would expect that to be reflected in the air temperature immediately surrounding the beans, like an ice cube in water.

In my recent attempt at a true dark roast with the Ikawa, I found that it only took a few degrees of over-temp to trigger a crack in a reasonably short time, and then hold that temp to within a couple degrees for several minutes - crucial to avoid scorching the beans. Does a drum roaster have that level of control?

Thanx....heading to SM now. I should read more articles on their site.

is there a limit on how many roasts one can do at a stretch?

Great question. The Ikawa Pro says it can do 60+ roasts a day, back to back. I couldn't find that specific information for the Home version, and I would be curious if the Ikawa Home is similar. Not that I would ever do that many!

That's like 7 pounds of roasted coffee, I can see someone doing that for the holidays for gifts. I'll be roasting for the holidays too, but in my Bullet.

I do 3 back to back whenever I roast. At some point I'd assume the system has stabilized and an additional roast makes no difference to the roaster, I'd guess somewhere between 1 and 7 roasts will reach that point, once you're there, all one more roast does is run the fan motor more which is the the part I'd consider most likely to fail. I think those numbers are stated to both define warranty limiting usage and insure machines last through warranty and not likely anything else.

Ira

I did around 15 back to back roasts 2 weeks ago, did not even think about it. Also I tried some of the beans I have other then Ikawa's with ok result. For example I had Columbia Gaitania washed, used profile for Guatemala Blue Aryza and it was good. Again tried the same with my Decaff (using decaff profile from Ikawa) and roast has some oil on the beans, so next time I will try lower temperature. I mean I just play around my knowledge is very limited.

I am not sure how this will go with other beans then Ikawa's but still I am thinking it is my knowledge. I think I will take some roasting class, with learning how to taste the defects and what to change.

I tried contacting Ikawa ( pre-sales) via email about 10 days ago. No response.
I ended up purchasing the Ikawa Home on 12/27.
I have not heard from them since then.
I even tried contacting Ikawa Pro USA and Ikawa UK by phone.... and left a message. Nada....
Also, what about if I do not like it within the 30 days windows. Should I return it all the way to UK? ( I live in Houston, TX)
Any thoughts?