Here's a graph showing some roast parameters in relationship to Tonino colors. The strongest correlations to T color appear to be % loss and the final temperature in this subset. I started tracking roast metrics and accidently lost the grind setting, which threw off the readings. I'm using a normal espresso setting and its dialed back pretty close......

(In the Tonino scale lighter roast colors have higher numbers)

If one looks at a spreadsheet with a variety of origins and processing, there's going to be outliers. Haviing a large database would help identifying correlations.

(chiapas 460 grams-16.9% weight loss-102 tonino color-216.3*c drop temperature-14:09 total roast time-3:15 roast development time after 1C)
(the last roast has a higher color and with a shorter total roast time)

weight % loss tonino end *C time RD time Mexican Chiapas

460 16.9- 102- 216.3- 14:09- 3:15
454.2 17- 107- 218.1- 12:51- 2:51
454.5 17.1- 105- 217.6- 14:23- 3:05
454.2 17.1- 103- 217.7- 12:42- 3:03
460 17.2- 104- 218.1- 12:45- 3:00
460 17.3- 93- 219.4- 12:57- 3:03
454.5 17.5- 94- 219.5- 14:05- 3:08
454.4 17.5- 99- 219.2- 12:38- 3:00

Thanks for sharing some data, Hank. When I have more time on my hands I'll have to put that in Excel so I can plot it, as it is hard to make much sense of it by eyeball.

another_jim wrote:In terms of getting reproducible roasts; the mega-roasters (Nestle, Maxwell, etc) are increasingly using chemical sensors to end the roast. Obviously, they use super precise profiles; but batch to batch variation on the green beans makes the results not entirely identical. The sensors "smell" the level of two gasses, one that declines as the roast proceeds, and one that increases. The idea is that the changing ratio of the two gasses precisely correlates with degree of roast, more than does temperature, time, weight, or color.

Details have been sketchy, since everything about it except the bare idea is a trade secret. So I have no idea which gasses, what levels, etc. are used. I also have the impression that it's still a work in progress; so if you happen to know how to design highly specific real time chemical vapor sensors; you can get a cushy job with the big coffee roasters.

I suppose the best chemical sensor I have access to is still the one on the front of my head. Still, I'm not sure how reliable its judgments are from roast to roast regarding stopping time. I tend to always use time and temperature as checks on what I'd do based on smell. Perhaps it is worth deliberately ignoring the data for a while and seeing how much consistency I could get from smell alone as a guide to stopping time...

Sorry was unable to post the excel spreadsheet, it is interesting to play around with sorting the columns.
All the parameters one would expect can affect tonino color, final drop temperature, RD time, and total roast time.

I just checked a bag of traditional espresso blend and got a 90 tonino color. That's a little lighter or less development than just looking at the beans; although they are not oily. According to the bag its a Brazil blend from Carmo de Minas, and now with the two pieces of information I could go back to my database and find a profile that's close. The espresso blend I threw together has a tonino color of 78, and the component that went into second crack is oily. It tastes ok but going into second was probably a mistake. You don't ned a colorimeter to discover a roast is too dark, like Susan said it's another tool or metric that could possibly be put to use.

I am jealous. I never seem to be able to drop my roasts until after they have dropped below that 100 mark. Something in me just won't let go soon enough....
Hank, were those roasts on the HUKY or on your Mini?

[creative nickname] wrote:...Perhaps it is worth deliberately ignoring the data for a while and seeing how much consistency I could get from smell alone as a guide to stopping time...

I don't ignore data; very helpful. But I am relying more and more on it to use in building my visual and smell roasting skills. Slow, methodical, but I am learning.

[creative nickname] wrote:I suppose the best chemical sensor I have access to is still the one on the front of my head. Still, I'm not sure how reliable its judgments are from roast to roast regarding stopping time. I tend to always use time and temperature as checks on what I'd do based on smell. Perhaps it is worth deliberately ignoring the data for a while and seeing how much consistency I could get from smell alone as a guide to stopping time...

I drop by smell as well. But unlike the chemical sensors, I'm looking for an event -- no more vinegary/grassy/raw smells for a really light roast, hint of caramels for a medium one, hint of distillates for a darker one.

The trouble is that it's not super consistent. But it works really well for roasting something the first time; for instance, by checking the vinegary/grassy/raw smells, it's clear some coffees can be dropped halfway through the first crack, while others need to go past the first, even for a light roast or cupping.

SJM wrote:I am jealous. I never seem to be able to drop my roasts until after they have dropped below that 100 mark. Something in me just won't let go soon enough....
Hank, were those roasts on the HUKY or on your Mini?

Those were done on the Mini where the drop temp was just before the onset of second crack; what I would call a full city roast.

another_jim wrote:it's clear some coffees can be dropped halfway through the first crack

Thank you for that. I had no idea. I thought I was doing well by trying to make myself drop soon after the end of FC, but....even before that? I will have to try it.

Very Interesting topic! ...

I've been wanting to ask all of you a somewhat related question. For lighter roasts - city and city plus. What is your average ROR from FCS to drop ? I know that question can't be asked in a vacuum as how you're progressing through that development period is contingent upon choices you made earlier in the roast (energy built up, etc)... as well as what kind of bean you're roasting.

However, looking at Boldjava (Dave Borton's artisan profiles on some of the mill city beans) - I'm very surprised how low his ROR is through that ~2 minute time period.... Under 3-4F/min. I haven't experimented with a roast to test that theory of such a "trickle" of heat but I'm very curious...

Dave since you're in this thread I'd love to hear your thoughts. I've always been around a 10-13F average BT ROR if I'm doing a city/city+ roast. If I was a 3-4F that would seemingly be less than 7-10F temp increase from FCS to drop (that seems far too low?)

edit: sidenote - if this is a thread hijack, I'm really sorry, you can pm me if that works better.

Thanks!!