Marko Luther is a very prolific coffee innovator with products like the
Tonino roast color meter which compared to the competition is
at least as precise for a fraction of the price.
Still, he may be best known for the free-for-all
roast logger Artisan which he has been upgrading and updating intensely over the past years.
Last week Marko posted two new blogs which are both very interesting.
First he shared a very thorough exposé about
PID control, explaining the basics of PID and detailing how Artisan now offers PID control even for those users who don't have PID hardware. If you have a device that influences your roast profile and you can regulate it with a slider in Artisan, then you can use Artisan's software PID to "cruise control" your roast.
Then Marko unveiled yet another new feature of Artisan called
Area Under Curve, based on a concept that was discussed on the Home-Barista forum.
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| AUC= Area Under Curve (sketch by Marko Luther) |
The idea is that you can define a certain significant part of the curve, for instance starting at 110ºC or right at the Dry End point and calculate how much 'surface area' there is until DROP at the end of the roast.
How is this useful?
Imagine your aim is to repeat a previous roast. You might observe that the Bean Temperature curve has been a little higher than planned early on, then a bit lower and the curve gets less steep in the very last phase. Now do you wait until the BT has reached the same end temperature as in the previous roast, do you try to keep the development phase (the part right after First Crack) timed like the previous roast, do you compromise or do you even revert to other criteria such as checking the visual appearance of the beans, trying to remember how they looked the other day?
Artisan now offers a new assistant. If you have loaded the previous successful roast in the background, you can read the target number for Area Under Curve on your screen and if you select the option, you can see an LCD field with your current AUC number or a countdown to zero of the area that you need to cover to reach the same figure for your current roast. Plus there's a vertical line that shows you at what moment in the near future you would need to end the roast at the current rate.
I tried it out. These are my settings:
I opted to calculate AUC from the Dry End point onwards. The possible advantage is that I could compare the numbers with a fellow roaster, even if he / she has a different machine with Dry End at a different measured probe temperature. I also selected "Background" as the source for my target.
This is the profile I wanted to reproduce:
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Guatamala beans, end temp 198ºC in 13:42, 27% development, Tonino # 93 result
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As you can see in the above profile, the Rate of Rise soared a bit running up to First Crack and then gently subsided. I used extra fan speed at the start and just before First Crack. One heating element was shut off a while before First Crack.
This is the profile of the subsequent roast with the above roast loaded in the background:
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| Guatamala beans, end temp 190ºC in 13:27, 25% development, Tonino # 94 result |
At the start, Bean Temp was a little lower than planned, then from around Dry End up to First Crack the Bean temp was a little higher all along, indicating that more energy went into the bean mass. One element off after 9 minutes, the second before 14 minutes and the third a little later. With slight increases of Fan speed I aimed to avoid the significant 'bump' in the Rate of Rise and the profile showed only three soft bumps up to First Crack. After First Crack the Bean Temp stayed a bit below the plan but the countdown LCD and the vertical line suggested I stop the roast at about the same time as in the original roast.
I followed the suggestion, ending maybe a fraction sooner as soon as I saw "25%" development time and the result was a roast color of Tonino #94 which is practically identical to the #93 I was aiming for.
I will play around more with these new features.
Thanks Marko for providing these!
