I'm starting this thread off of the comments in the "First Annual HB Home Roasting Competition Tasting Notes" thread. I think this will become more needed as we do more comparisons such as with the "Roasting Competition".

another_jim wrote:It's hard enough putting good numbers on bean temperature; ET is really tough. The profile JimG posted would translate to about 15degrees higher on bean temepratures and who know how much higher on ET. On the other hand, the profiles Rafael is posting using the same roaster I am shows higher temperatures all round

So all the advice is more or less qualitative.

I think a collective project to work out a method for calibrating temperature measurements across roasting systems might be fun -- maybe impossible, but definitely interesting.

another_jim wrote:The first crack makes one good calibration point, but I think a second calibration point is also required. The measured temperature is a combination of room temperature, the roaster's heat source temperature, and the bean temperature. So, it'll be like calibrating anything, we'll need a two readings to get the span and zero.

I think that 1st crack is an obvious 1st measurement to use as will be fairly profile resistant. It's finding a 2nd point of reference that will be tricky as something like 2nd crack or other points will be more effected by the profile for comparison.

farmroast wrote:I think that 1st crack is an obvious 1st measurement to use as will be fairly profile resistant.

Ed,

I look forward to learning from you all, and I am glad you split this into a new thread.

But we may as well be as specific as possible about "1st crack". What about a stray/early pop or two? Ignore them as outliers?

What are some situations when 1st crack might be very soft and subtle? Is it the greens, the processing of the greens, or was our drying phase too long?

Not sure where you want to take this thread, and I sure don't mean to hijack it.

The 395F/200C figure for first crack is for the "average" new crop bean with average moisture content (aka a washed Colombian supremo). So you would probably want to take the height of the first crack as the marker (I think the first crack temperature distribution is a bell shaped curve with the high temperature tail much longer than the low temperature one, but I'm not sure).

In any case, my experience is that it is pretty consistent roast to roast on the same roaster, even if the time to the first is shorter or longer. I'm much more pessimistic about the second crack as a reliable marker, since I get 10F differences depending on the roast speed.

I'm wondering if something like the Omega temperature crayons could be used. This particular crayon liquifies at its target temperature, which sounds mildly alarming. I'm wondering if there are somewhat more food safe alternatives