What are the lumps in the BT and ET roast?

[thusband]

One of my first roasts and I'm wondering what are those delta BT and ET lumps in the middle?  The BT and ET temp seems to be rising pretty smoothly. 

So much to learn but so much fun.

[edtbjon]

Those humps are indications of a temp change. The BT (and more visibly the ET) curve(s) does make small but visible rises and dips. It's like driving a car in a "constant" turn and then the banking of that turn changes ever so slightly. You cannot really see that change but you have to adjust for it.
You don't say (or graph) what you're doing with the gas and fan, but I normally act on that change (which is typical) adding a bit more fan (from 10% to 20% or something like that).
Apart from that is seems very good, except from the end, where you obviously did strangle the gas too soon. I normally go into 1Cs (start of First Crack) with say 40-50% gas. Just before 1Cs I also normally increase my fan to 50-60%. I than hold that gas setting for about a minute into 1C and then I go down with the gas (in increments) to 20-30%, which usually is where I'm at when 1C finishes and it's time to dump the beans.
(Roasting is like one of those long distance runs in the track and field competitions. They keep slowly jogging around the track for 24 laps, looking at each other just to save all the action for the last lap... )

[thusband]

Great!  Thanks, it's a bit more clear.  You're right, I forgot to track the fan and gas.  Too much going on.

[edtbjon]

Just to make it more clear. The BT curve itself should rise from the turning point upto the end of the roast. The idea is to build a momentum which should last throughout the roast and never stall. The Delta BT curve (also named RoR (Rate of Rise)) shows the momentum itself.
Going back to the car/steering wheel analogy, the BT curve is like the road, which (for the sake of this discussion) seems straight, but all the small adjustments you make with the steering wheel is denoted in the Delta BT curve. (Please note I'm not saying that you are making constant changes to the gas and air, the steering wheel analogy is just me trying to describe the shape of the RoR curve.)
Thinking about it, it's a rather good metaphor. It's easier to drive a car when you fix your focus point far ahead of the car, else the ride will be very wobbly. The same goes for controlling the roaster, i.e. the changes you make are intended for the final target, or at least a couple of minutes ahead.

[thusband]

OK got it.  So ET delta isn't too important?

Thanks again.

[SusanJoM]

As an aside, the small bumps (not the ones that you were really asking about) can be smoothed so that they are less distracting and the overall direction of your curve is better represented.  Under Tools > Extras > Graphs you are given options for "smoothing" curves and spikes.

[thusband]

As an aside, the small bumps (not the ones that you were really asking about) can be smoothed so that they are less distracting and the overall direction of your curve is better represented.  Under Tools > Extras > Graphs you are given options for "smoothing" curves and spikes.

Thanks, I'll check that out.

[edtbjon]

OK got it.  So ET delta isn't too important?

Thanks again.

It's not as important as the BT (and corresponding delta values), but IMHO, both (three if you include MET too) does bear significance. As a start, they should not differ too much, which is acquired by doing a proper pre-warming of the roaster. (I always start a session by starting up the roaster and the heater. Then I assemble and start up the exhaust fan at a low setting. Connect the computer and start reading the temp. Get the beans etc. together, including bags and stuff. I don't mind having the roaster idling at loading temp for e.g. 15 minutes or so.)
After a decent warm-up, the three lines should run steady and parallell.
I personally pay almost all attention to the BT values. But for the sake of discussion, the MET is mostly controlled with the heater, the ET by the heater but more so by a change in the fan setting. The BT is of course a result of how you control the heater, but as the name implies, is closest to where things really are happening. (I may be wrong here, but as I said, "for the sake of discussion"...)

[thusband]

Thanks again, very informative.

[SusanJoM]

OK got it.  So ET delta isn't too important?

I got rid of Delta ET.
That doesn't mean it's not useful, but I was not using it and it just added to the visual noise.

[thusband]

I got rid of Delta ET.
That doesn't mean it's not useful, but I was not using it and it just added to the visual noise.

I can see that.  I'm a bit overwhelmed with the information I have now.

[hankua]

One thing that does matter is delta BT/ET, or the spread between the two. I don't see where Artisan tracks this metric, but it does show on a thermometer or the the two curve lines (BT and ET). In theory BT is always going to try catching up with BT. The greater the difference = high BT ROR; conversely the closer they are indicates a slow BT ROR.

For example: if your roasting really light the BT and ET need to converge at or before 1C so the drop temp doesn't get too high. If 1C is 200c for example, drop temp. could be say 204c. To run that low a ROR for 1:30-2:00 the ET needs to be lowered during RD phase. But if your looking to hit 2C in 3:00, then hitting 1C with more energy is necessary. It's easier to add heat than take it away; with the Huky.

[thusband]

Again, a bit overwhelming but we'll get there.

Thanks!

[hankua]

Looks like a drip roast by the RD time and ending temp. The initial charge temp. Was very low, was it a 1/2lb or less charge weight?

[thusband]

Actually there wasn't any plan to the roast.  It was a pound of cheap break in beans that I'll toss.  Practice only. Plus I forgot to hit the charge button right away.  The RD times are getting better the more I roast.