New guy here.

Back story: 53 years young, poor-mans coffee lover for 46 of them. ROK manual espresso maker at home and Aeropress at work. Baratza Preciso grinder. I like a cappuccino in the AM and espresso after that. 3-4/day total.

I've been trying my hand at coffee roasting. I started with an AirCrazy but fried it in a couple of days. I learned enough from that to know that I want to do this some more and need a larger capacity. Graduated to a Turbo Crazy rig and have been through a dozen or so pounds, 1# at a time.

I know nothing about cupping, grading, roast profiles etc. I just love good coffee and don't want to spend a fortune (yet) making it. I have some Sulaweja Kalossi and La Minita beans to work with and plan on buying lots more.

I made a little video last night of a roast and would love to know what was happening. My thermocouple is mounted on the bottom of the SC and is fully covered by the beans, so I should be getting bean temp, but I'm open to any and all suggestions, thought, comments etc.

Glad to be here!

Welcome Alan! It is a exciting new world you entered

One of the joys of home roasting is trying the same beans at different levels of roasts. Steep learning curve as long as you are organized in going about it, and don't forget to have fun!

Welcome here! I didn't watch your video but that curve is interesting. Usually you don't want your temp to fall after the turnaround point.

zammie wrote:Welcome Alan! It is a exciting new world you entered

One of the joys of home roasting is trying the same beans at different levels of roasts. Steep learning curve as long as you are organized in going about it, and don't forget to have fun!

Have fun...check! Wait, do people really take this seriously?

The La Minita is the only batch I have in quantity so far. I've roasted about 10# of it and have another 10 to go. I've tried everything from a City roast to a Vienna. I'm finding I like this bean at a FC roast, just till 2nd crack. But I'm still learning how to control my roaster. I like taking videos of my roasts so I have a record and can go back and watch at my leasure and makes notes.

Bodka Coffee wrote:Welcome here! I didn't watch your video but that curve is interesting. Usually you don't want your temp to fall after the turnaround point.

You didn't miss much not watching the video. Bit of a sleeper.

I'm not sure why the temperature drops. I'm keeping the SC element ON the whole time and the TO is all the way up. Without beans it will get to 465*. The thermocouple is on the bottom so it is completely covered by the beans. I warm it up to about 440* and then add the beans. BT usually bottoms out around 315* at 1-1/2 minutes and then started to climb. It will get back to over 400* until just before 1st crack and then all through 1st crack it's about 365*.

Could it be possible that then temp is dropping when the beans are releasing their moisture and maybe it's this steam that is affecting the reading?

Check out the roasting forum threads. We have a Roasting and Learning Together thread as well as Tom has arranged a roasting contest for March. See this forum.

Welcome.

Almico wrote:Could it be possible that then temp is dropping when the beens are releasing their moisture and maybe it's this stream that is affecting the reading?

Possible is a word encompassing a vast universe. Let's limit it a bit and say that your hypothesis is an unlikely explanation of the observed phenomenon.

Bean temperature is really "bean mass temperature," which is itself something of an artificial construct, a "pastiche," if you will, composed of several different elements.

During the period of exothermia, you'd expect the bean mass temperature to increase almost independently of the amount of heat put into the system. But the dip in your reported temperature almost exactly overlaps it. Unless energy is being sucked out of the system in some way, the dip probably has more to do with the air-stream and probe placement than the beans themselves.

Rich

For this set up, put your thermocouple at the suction end of the turbo oven -- that is getting the air coming off the beans and will be the best approximation of bean temeprature. Putting it at the bottom gets the heat from the stir crazy plate as well as the heated supply air of the turbo.

Thanks Jim. I'm not sure what you mean by the suction end of the TO. Do you mean to mount it on the TO itself somewhere on the center grille?

I also have another TC that I was going to install in a hole drilled into the aluminum ring to measure the air coming out of the TO. What if I leave the one on the bottom, but keep the SC off?

I guess my question is, is there any value to having a TC in direct contact with the beans?

In any roaster with a lot of airflow, the average bean temperature is nearly identical with the average temperature of the air as it leaves the beans. The best model for the bean/air interaction in these roasters is a cross-flow heat exchanger.

There were lots of different turbo ovens, and I am not familiar with the airflow on all of them. But they all must have a point where the fan sucks in the air from the oven chamber and sends it back over the heating elements. From a control point of view, this is a fairly stable spot to measure the bean temperature; while the air coming off the heater is a nice stable spot to measure the maximum environmental temperature.

Your measurements may be identical with other roasters, but they will be linear with the true temperatures. Your current recording spot is clearly not linear with the bean temperature.