IBTS Drop Temp for Various Roast Levels

Anyone have an IBTS drop temp chart for roast levels from city to full city+?

Here’s something from Sweet Maria’s that I found to be pretty close to what I see on IBTS with 450-550 gm batch sizes even though it’s created from thermocouple data. I recently tried an 800 gm batch and a 1 kg batch- at these batch sizes the correlation was not there so tread carefully.

Bruce

Edit- I just reviewed the 0.8 & 1.0 kg roasts and now realize that IBTS data does correlate across all batch sizes I’ve tried. What is different is that at both these larger batch sizes Bean Temp is higher than what I expect to see at my usual 550 gm batch… BT is very close to IBTS at the end of the roast with 1 kg batch.

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So, to get to FC+. you are dropping at 454F on the IBTS? That sounds awfully high to me.

It is awfully high. So I have had to drop at 441-442°F for FC+. 454°F is more like Vienna as I see a lot of oily spots. I started out treating the SM article as gospel then adjusted to my own set of standards.

The issue is the subjective nature of C/C+/FC/FC+… etc. When I was given a link to Roast Vision I finally saw a decent way to get an objective measure of roast color. Unfortunately the measurement is post-roast. But at least I now have a way to confirm some of the temps I use for dropping the beans. The scales don’t match so I had to adapt for my own use.

And I’m finding there are additional considerations that affect the roast color such as the batch size and the rate at which you approach the target temp. So it’s a work in progress.

Bruce