Roast degree descriptors with temp parameters

Can someone provide IBTS parameters in either fahrenheit or celcius for the following descriptors:
city, city+, full city roast
When I get my greens from Sweet Maria’s or Bodhi, the recommended roast level is stated as a descriptor rather than a temp range … that said, I have used search engines to try to pinpoint the temp ranges but they are so varied based on interpretation…can any of you provide some guidance on these degrees of roast in the form of suggested IBTS temp ranges on the Aillio

Try this from Sweet Maria’s. It was done using thermocouple data but seems to come pretty close to IBTS readings. It uses reference to C/C+/FC… etc.

Data you get from non-Bullet sources will probably be thermocouple based. Thompson Owen uses sight in determining degree of roast (you’ll need to use the tryer).

Bruce

Edit: the images provided in that article were probably created on a Mac using the Pantone scale that he talked about years ago. The issue is calibration of displayed color. There isn’t a color standard supplied with a Windows system though there are adjustments. Thanks to all the variables involved in adjusting the display it’s really hard to get commonality (it was much worse with the old CRT displays).

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I had the same question recently, and got a bit of guidance from some helpful folks on the Aillio Slack channel. This spreadsheet is my attempt to correlate temperatures from a few online sources (Sweet Maria’s & a couple other Google search results) with info gleaned from the discussion on Slack and my own (very limited) experience. Temperatures are in Celsius. I’ve recently received the Roast Vision USB doohicky from EspressoVision, which will give you an objective color analysis of your roasted beans, and from tests of a few batches I roasted today, this data seems pretty reasonable for 1C/City through Full City, but the values for Full City+ and up are projections, as I haven’t yet roasted that dark to validate the data. The spreadsheet assumes first crack comes in at 200C on IBTS – which is my average – but if it happens cooler or hotter, you’d want to adjust up or down accordingly. I’ve not yet added in the bean probe temperatures.

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Great info. I’ve always thought I was roasting into FC, but most of my roasts appear to be City to C+. I looked at the Sweet Maria’s info that Bruce shared, which is very good, but would be afraid of roasting as high as those temps for a FC using the IBTS.

This is an excellent discussion. I have been roasting coffee for over 20 years and using the Ailio Bullet approaching 2 years. To me the machine is revolutionary as it provides IR temp reading of the beans and uses induction heating. I have read that others have said that a Bullet induction roasted bean is lighter in color than a similar bean roasted with with heated air. My personal experience is that the latter is a true and important fact. Therefore any color system is likely not going to translate to bean development using the Bullet vs almost any other device. I have been using first crack as a key reference point and development time from the beginning of first crack and end of roast. Because my taste has changed ( to eliminating the burned flavors from my coffee), I will almost never roast any bean much beyond the end of first crack. That being said, Jeremy"s spread sheet is interesting and the IBTS temps for first and second crack are pretty close to being true. I have recently been following one of the Roast World posts and place a hearing tube into the the tryer opening. This is particularly useful for beans with a low decibel first crack and it also picks up the beginning of first crack often 10 to 15 degrees F earlier than than the numbers in the spread sheet. So I would recommend being very careful if you are using a color designation as an important indicator of roast development in particular if it was determined by non bullet roast equipment.

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Nice sheet @Jeremy ! From my observations on IBTS, I agree with 1C, City, and City+, I never go much further. @melepstein 's listening observation is likely right. I’m always thinking I’m about to hear 1C and then waiting to really hear it at ~198-200C.

How about people’s feeling on Yellowing? Given how difficult it is to consistently pick a shade of Yellow. I like the idea of noting the time that it reaches ~165 C. What do you all think about the 165 temp?

I’m there with you.

I’ve been marking yellow when there are no more green beans (my interpretation of what is done in Mill City Roaster’s youtube videos.) That actually seems pretty reproducible, but may result in a later/hotter mark than others use. Been considering switching to a temperature milestone instead of color. Seen some gas roasters mention using a milestone at 300F or 150C, which is probably around 165C IBTS, so I’m curious to hear arguments on this…

Hey Brad-

I went to a fixed-temp substitute for Yellow point quite awhile ago. I was using BT = 300°F/149°C. It served double duty: mark the yellow point (more like yellow-tan which fits with data I scavenged from Sweet Maria’s) and also serve as a standard measuring point to keep track of the difference between BT & IBTS for IBTS maintenance purposes.

Then I noticed BT can vary at the end of the roast depending on batch size. That’s when I realized I didn’t have an objective certainty that batch size didn’t affect yellow(-tan) point. So I decided to switch to IBTS as the color-change point for the sake of consistency. So my new reference point is IBTS = 350°F/177°C. I think it might be a little dark for color so I may have to go to 340°F/171°C but I like having the grid line. It’s a work in progress…

Bruce

Bruce I think you are spot on. My roasts are mostly 250 or 500 g. For the same degree of roast, the 500 g batch ends at a lower temp than the 250 g batch

I really try to use visible color, and it is most often at 160C to 165C IBTS for my 454g batches.

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An update on this work? I’ve just begun roasting, but it does seem like IBTS temps are lower at the end of FC than I’m used to, and more in line with your spreadsheet. But, still very new to this.