Can you hear Second Crack?

I have often seen people crib about not being able to hear First Crack. Some have improvised stethoscopes for it. Coming to the Second Crack since most appear to drop before it, I wonder if anyone who does roast to it and beyond has actually managed to hear it?

I, for one, am unable to hear it.

I just got my Bullet from this last wave in April and am just getting around to using it and doing my initial seasoning roasts. I’m still working out a permanent home for it, so for the time being I’m roasting outside where there’s slight road noise.

Since I’m seasoning, I’m charring beans past 2nd crack, and I can actually hear 2nd crack better than 1st crack - but I find both cracks hard to hear until they start to get rolling. That is to say, trying to hear when both cracks “start” is proving difficult so far. The type of bean probably plays a role, too - some beans are quieter than others.

Can’t wait to get my bullet set up indoors… hoping that will help me being able to hear stuff…

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A few thoughts…

I don’t have a stethoscope. At around the time I expect 2C I tip the bean chute cover sideways so the underside of the cover reflects sound toward my ear. Works fairly well for 2C; works very well for 1C.

Decaf is very quiet at 2C, but that’s how it is. I have to depend on temperatures and do my best confirm that it’s going on. I usually miss the start of 2C with decaf.

And I have hearing aids which may or may not help since they amplify stuff I don’t want to hear (like the beans tumbling in the drum) as well as the good stuff.

One last one: if you see a few small circular chips falling into the cooling tray during the roast (about 1/8" dia.), 2C is already going on. They don’t always show up on the tray surface but if I hit 2C I almost always find them beneath the cooling tray when I vacuum chaff if I look closely.


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Bruce does using the bean chute cap to listen for crack have any heat loss effect on profile?

There’s probably a change in air flow. The exhaust fan creates a lower pressure in that area so air may be drawn in thru the bean chute instead of from the drum area. A listening device mounted in a replacement bean chute cover would be a better choice (stethoscope? mic+amp+speaker?) but I haven’t seen any dramatic temp change from listening there. I listen for a few seconds, close it and wait, listen for a few seconds till I hear it. The sound thru the bean chute is significantly more distinct than thru the walls of the roaster.


Thanks Bruce, I notice recognising the crack in the Bullet more of a challenge.

Second crack is tough to hear. I haven’t tried to implement any of the hacks suggested in the other threads, but sometimes I have been able to hear 2C through the trier port (taking the trier out). The sound is like rice crispies crackling when your pour milk over them - it’s faint. Sometimes I don’t hear it at all which seems to depend on how the roast developed and possibly the (age - i.e. how long I’ve had it) of the beans. My last round of roasting I barely heard 1C while other times I hear 1C pretty clearly.

Thanks for that. I suspect I don’t always mark the very first crack but usually not far off. When I compare my FC timer mark I am a lot earlier than others eg 6.30 or early 7 mins, but figured this was as I am only doing 350g batches.

I am also not confident about when to click the “yellowing process” but reading others views am just going with “what feels right to me” when I feel no Green tinge remains (and already noticing different green varieties produce different results eg Monsoon Malabar is a very yellow bean naturally.)

You can get faked out with 1C. I wait for the 3rd pop before marking as suggested by @stuartmcknight

Yellow point has become a fixed temp for me. Color identification is hopeless as some beans are turning yellow → tan at the same time others are still clinging to green. It’s too subjective. So I arbitrarily chose IBTS = 333°F as YPt. Works for me but YMMV. If you have a blend with robusta those beans start out yellow anyway,


I slow drum speed after 6 minutes to D8 or D7 to hear the cracks.

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