First crack - what exactly are you listening for?

December 29th, 2022, 2:47 pm

Searching this and other forums, I understand there are sometimes a few isolated pops that occur before truly reaching FC, so I ignore those and wait for "true" FC -- but I hardly ever hear a "rolling" popping like a bag of popcorn, and when I do I find that have really overdone it.

Question: What does a "normal" first crack sound like to you and how long does it last? Do you always wait to hear a fairly brief (like 20 to 30 seconds) period of a "rolling" first crack before you determine you have reached "true" FC? Or is FC sometimes just isolated popping here and there over a longer period (like 60 to 120 seconds)?

(Machine/coffee might not matter much for this question, but I'm using an SR540 with various typical unblended coffees like Panama Premium Washed from Burman. I'm using the typical methods recommended on YouTube for the machine, like 10 minutes on average.)

December 29th, 2022, 5:07 pm

I think the most important thing is to use a consistent method of marking first crack more than anything else.

For me, after a few random outlier pops, as soon a I hear several in a row I mark first crack. Depending on the coffee I'm roasting and roast profile, first crack may then proceed quickly with lots of pops, or more slowly with intermittent pops.

It's also helpful that I use thermocouples and logging software, so I have a pretty good idea of the temp first crack will start at for different beans too.

As to length of first crack I rarely listen for that because I roast to +X degrees temp after first crack start, then drop.

#3: Post by **rmongiovi** » December 29th, 2022, 7:56 pm

I've always assumed that how "rolling" your first crack is really depends on how many beans are in your batch. I don't roast more than 1/2 pound so I ignore the first couple as outliers and declare whatever comes after as "first crack." How steady my cracks are seems to vary from bean to bean but they're never really pronounced enough to discern a clear end. I don't fret about that too much since there's nothing I do that's based on that anyway.

#4: Post by **mkane** » December 29th, 2022, 9:00 pm

A few pops in a row and marked. Usually lasts between 1:30-2:00. I start sticking my nose on the trier @ 1:30.

If I get a rolling 1C, really rolling I'm headed for a crash. Batches are 370g

#5: Post by **minus1psi** » December 30th, 2022, 9:31 am

In the Mill City series "Roaster School - Season 2 - Episode 3: From Yellow to First Crack" Derek DeLaPaz tells Joe Marrocco that he listens for three pops in a row, pop-pop-pop not (pop-pop----pop) or (pop----pop-pop). The link below tries to go directly to that part of the video but for some reason only gets close. The key moment starts around 20m 50s.

http://www.youtube.com/watch?v=IQMRWt9KpRA

In a completely different video, "Rob Hoos talks coffee, roasting, RoR and covid with Devin Connolly" Rob Hoos offers the amazing insight that he calls 1C dynamically based on sensing the smell of vinegar.

This link goes close to that part of the video (actual moment starting at approx. 21m 40s, the link seems to be a few seconds ahead of that time). http://www.youtube.com/watch?v=nxn4DFw1J-w

my notes...

Q: What do you think of marking 1C with a dip in inlet temperature?
	• possible depending on sensitivity of your probe and the design of your machine (Imo the vibe was not to go that route -LD)
	• you should be dynamically calling 1C every single time
		- I do it by smell, it smells like vinegar. The decomposition of sucrose sugar
		creates acetic acid (vinegar) as a by-product
	• important to call it dynamically because the time from 1C to drop determines
	the whole bean to ground bean color differential (how roasted the inside is)
		- if you say 1C is always 200°C (or whatever) you will end up in a situation
		where you did not call 1C appropriately because for whatever reason it did not
		happen at 200°C. That means the color differential between your whole beans
		and ground beans will be different resulting in an incorrect ground color
	• BT is not a reliable way to call 1C
		- if machine is operated exactly the same way everytime marking BT
		by temperature is fairly accurate assuming all conditions are the same
		- if anything varies, like you're running your burn way different or your air 
		flow way different then you will probably get a different reading than you're 
		accustomed to on your bean temperature

[edited to remove some random personal comments]

#6: Post by **mkane** » December 30th, 2022, 11:05 am

#7: Post by **Nunas** » December 30th, 2022, 3:25 pm

If you have too big a load or too low a heat, the ROR will be too small to establish a rolling 1C. Conversely, too much heat or too small a batch will overdo things. As others have mentioned, I listen for consistent popping, not counting the odd stray early pop. As for how long 1C lasts, in terms of time, it depends on load/temp (ROR really). But, in terms of temperature, I find it lasts for about a 17-degrees C rise. On my roaster, 1C start with nearly any bean, happens at 200 degrees C, give or take a degree or two. Of course, reported BT temperature in your roaster may vary, as a lot depends on where your BT probe is installed.

#8: Post by **drgary** » December 30th, 2022, 5:20 pm

I'm getting rolling 1C without a crash when roasting a dense natural coffee light and somewhat fast. I'm starting with a relatively low charge temp. So, it depends.

#9: Post by **Milligan** » December 31st, 2022, 1:16 am

Lots of good responses. I recently wanted to see the relation between momentum into first crack versus what temperature first crack begins. So I set up a few test roasts. The goal was to head into first crack at differing RoRs and see the difference. Simply put, at around 20F/min my machine hit first crack at around 373. Going in at 15F/min it pushed it to 382F. I was quite surprised at the impact of momentum. I wasn't expecting that large of a difference. I still need more batches to play with before drawing too many conclusions.

I remember reading about the "vapor front" pushing into the middle of the bean causing first crack. So, the greater the heat gradient, the faster the vapor front hits the middle and with more pressure. A higher RoR would cause a higher gradient.

I've been messing with this a lot lately because keeping enough momentum to get to second crack without a wonky RoR after first crack can be challenging while also not crashing with too much momentum. I have much respect for masterful dark roast control.

#10: Post by **Marcelnl** » December 31st, 2022, 3:46 am

isn't that momentum simply the delay of the measurement, a higher temp increase per minute will have more impact than a lower?

I'm using three in a row with a glance at BT, nothing overly precise but I mostly disregard time since FC lately and focus more on drop temp as I find that a more reliable parameter than anything else.