First Crack FAQ: What is First Crack? What is Second Crack?

If you’re struggling to identify the sound of first crack and second crack when roasting coffee, read on…

I remember many years ago writing a post about roasting, with the advice to “lower the temperature just before first crack.” Someone commented, “how are we supposed to know what we are supposed to do when the thing we are supposed to react to hasn’t happened?”

I’m sure I wrote something back about “experience and anticipation” … but I knew it’s like tossing a curveball of an answer. How do you tell someone to “do something in anticipation of something that’s about to happen, but do that first thing just a bit before the second thing actually happens”. That’s a bad sentence and a bad concept. Luckily it’s just coffee.

And I hate to say it but you will indeed learn to anticipate that thing that’s about to happen, with experience. How will you do it? With your senses: sight, smell, sound … and a good thermometer too. Let’s start with some definitions though.

Roast Cupping Test – Sample 7, End of 1st Crack 412f – City roast. Thompson Owen, Sweet Maria’s Coffee Panama Boquete La Camiseta

What is First Crack?

Here’s the short answer: First crack is the sound coffee makes when it reaches about 395 to 405 fahrenheit (external temperature). It cracks because the water trapped in the bean creates pressure as it turns to steam.

What is Second Crack?

The basic answer is around 440 to 455 fahrenheit (external temperature), the buildup of Carbon Dioxide in the bean becomes too great for the increasingly brittle bean structure. Again the expansion causes an audible crack or snap.

What is First Crack, in more depth please?

Coffee is a dried seed, but has residual moisture in it of roughly 10-12%. In the roast process the coffee requires a lot of heat in the “drying phase” when the coffee turns from green to yellow to brown. When the internal temperature of the bean rises, the water bound up in the coffee is transformed to water vapor, that is, steam. As the moisture forces itself out of the coffee bean, we hear the first crack, a popcorn like sound, and can often see moisture leaving the coffee. Physically the bean enlarges and the crease in the middle may open up somewhat. As it opens, it can let go of the silverskin that was pinched by it, chaff. First crack is not solely due to the pressure from water vapor, but it is the main driver. Up until first crack, the dynamic of coffee roasting is considered endothermic, meaning that heat must be applied to the coffee to absorb in order to force the desired changes. First crack marks a shift, where coffee goes from being endothermic to exothermic as the energy balance switches, and rate of change in the bean can increase dramatically.

In more detail, what is Second Crack?

While the coffee roasting process is continuous, people who roast focus on the audible cues of 1st crack and second crack. While First Crack is driven more by the change from water to water vapor, second crack’s audible snap is the result more of Carbon Dioxide gas pressure ( as well as CO and N-2). After an initial release of gas along with steam in First Crack, pressure builds up quickly once again. And this time the bean structure consisting largely of cellulose plant material (like tree wood) has become more brittle. So second crack has a different sound, more of a snap, like when you add milk to Rice Krispies cereal. Second crack can fracture that cellulose matrix in a way that oils and gasses find it easier to migrate to the surface of the bean, or out of the bean completely.

Roast Cupping Test - Sample 9, City+ roast 432f
Roast Cupping Test – Sample 9, City+ roast 432f – Nearing second crack, but not there yet. Panama Boquete La Camiseta

How can I hear the difference between First Crack and Second Crack? Just listen …

I have said that First Crack sounds more like popcorn popping, and second crack sounds more like puffed rice cereal when you add milk, it snaps. That might not mean much to some people though. And in fact first crack is NOT exactly like popcorn (I hope, because the rapid popping of popcorn would mean a terribly fast roast)…

So I created a rough audio guide to the sound difference. Here’s my narrated tour of the cracks in an air type roaster …Have a listen:

What do the cracks sound like? First Crack and Second Crack Audio

Here are some alternate recordings I created in the past. This is First Crack of a wet process coffee in an air roaster, no narration. Exciting stuff! :

First Crack Audio File – Wet process coffee

and First Crack of a Dry Process coffee, also in an air popper, which can sometimes be quieter and more slow-paced:

First Crack Audio File – Dry process coffee

How else can I tell the difference between First Crack and Second Crack?

Besides the sound of first and second crack, there should be other clues. I don’t want to sound dumb here, but, well, first crack comes first, and second crack comes second. Before I lose you, the problem isn’t temporaly dyslexia here … it’s that in some rapid roast processes like an air popcorn popper they can blur together. Also, some coffees have more pronounced or subtle sounds. Older, past-crop coffee can have a very loud sound to first crack. Some dry process coffee can have a very subtle first crack sound, and I have even roasted some that seem to make no sound at all.

So in case you miss the audible cues to First or Second crack, here are some other things that help. They are not always true …but can often be true:

  • A coffee bean can look more patchy in color, with light and dark areas, during first crack, whereas by the time second crack is under way it will have more even surface color in a single bean.
  • The bean-to-bean- color variation should be farm more uniform in second crack.
  • If you could take out coffee from the roast and study it, there are subtle differences. Just before first crack the crease in coffee is usually tightly shut, and the edges around the flat side of the bean are sharper and more angular, After it enters first crack the crease can open slightly, the bean expands a bit, and as it does the edge appears slightly more round. See the photo below! As coffee heads into second crack the it has expanded more, and this should be a clear difference you can observe.
  • Second crack can seem more rapid than first crack.
  • In an air roast, much of the chaff has come off by the time the coffee has entered second crack. (Dry process has far more chaff, so this is less true with those coffees as it continues to release chaff for longer).
  • First crack does not have the same pungent roast aroma as second crack does.
  • The smell of first crack is more like grain, like bread baking, whereas second crack has more pungency.
  • In the early part of First crack you might actually feel some moist steam coming from an air roaster. The air coming out in second crack feels very dry.

What does First Crack look like?

The subtle difference between coffee that is just about to enter 1st Crack, and coffee that has entered it.
The subtle difference between coffee that is just about to enter 1st Crack, and coffee that has entered it.

If you could take out coffee from the roast and study it closely, there are subtle differences. Just before first crack the crease in coffee is usually tightly shut, and the edges around the flat side of the bean are sharper and more angular, After it enters first crack the crease can open slightly, the bean expands a bit, and as it does the edge appears slightly more round. (PS- I didn’t note the coffee this was in the image, but it might have been a honey-process or natural).

What does Second Crack Look Like?

I think I can answer this best by inserting a video I just made, covering first crack, second crack and the changes in appearance associated with each. I titled it: Coffee Class: First Crack, Second Crack, Coffee Roasting Development . I cranked out this video, geared toward the home roaster who can’t get enough info about the changes in the coffee bean during first and second crack. Ok – it’s not that little, it’s 34 minutes! This is a basic non-sciencey presentation to show how coffee changes in roasting, and what sounds and sights to expect.

Unfortunately the roaster is a bit noisy in the middle parts, but there is a lot of little nuggets of information in this presentation of nearly 35 minutes! Less than perfect, this video still has some good information.

Checking Roast Levels with Ground Samples

A great way (after the fact) to compare roast levels is to check the roasted whole bean appearance versus the ground appearance. The ground color can be easier to judge. Below, the first whole bean photo is the same roast ground in the second, and the third photo is same as the fourth.

First Crack FAQ … and Second Crack Too!

If there are questions you would like to see added, or clarifications you need to the ones below, please add a comment at the bottom of the page and we will address it. This is a work in progress!

(When I am referencing temperature in these questions, I am referring to the commercial shop roasters I have used. Temperature measurement in different roasters varies, based on thermometer placement, type, roaster type etc. So it can be hard to correlate roast temperatures from one instance to another. Use the numbers as a rough guide and check them against your own settings).

What time does first crack happen in the roast?

There is no set time that first crack occurs. Every roast machine or process is different. The range in roast times from green to first crack can be huge on different types of roasters. There are commercial roasters that can reach first crack in 45 seconds! And there’s a roast style in some Mediterranean locales where they roast 30 minutes or more until first crack! But to give a general range for home roasters, a small air roaster /popper can have a range of 3 to 7 minutes to first crack. A home drum roaster like the Behmor can be 10 to 12. Many small shop roasters of the 5 – 12 Kg capacity range reach 1st crack in 9-12 minutes. For quality, there is no “correct” timing for first crack. It depends on the type of thermal transfer, the batch size, the coffee, ambient temperature, and many other variables.

When does second crack happen?

Well, the short answer is, after first crack! Second crack should start after a pause of roughly 30 seconds to 4 minutes after first crack ends, with many roasters. Some fast roasters can merge first and second crack, which makes it confusing to make roasting decisions. But with most roasters that are not introducing too much heat during first crack, there should be a distinct pause before second crack starts. The “popping” of the coffee becomes more of a “snapping” sound like adding milk to Rice Krispies cereal (listen to my audio recordings above!) In some air roasters / poppers you can reach second crack in 6 minutes, whereas in a drum shop-size roaster you should see second crack just start in a range from 14-18 minutes.

What does it mean when first crack is very loud?

I have noticed that when green coffee is older, or more dried out, it can have a more percussive and louder first crack. So it might be a quality issue with the coffee. It also seems that less dense coffee, often lower grown, can have a louder first crack. (Conversely we have had some high grown dry-process coffees that have a very quiet and short audible first crack!)

At what temperature does first crack happen?

In my experience with temperature probes that directly contact the coffee, this will happen at 395 to 405 fahrenheit (201-208 C roughly). But like all things in roasting, there are no simple answers! We can’t measure the internal temperature of the bean with a probe, which would be the most consistent measurement. And most ways to measure temperature are not strictly reading bean surface temperature … there’s always some environmental influence. It also varies based on altitude. (You may also notice that, if first crack is water turning to steam, these readings are 2x the boiling point of water generally! But water vapor and boiling point are different, and dependent on other factors like pressure.)

What temperature does second crack happen at?

With the same probes I referenced above for first crack, second crack happens at a range of 438 to 450 fahrenheit (225-232 C). It has seemed to me that second crack has a more variable temperature range based on the coffee. Still, these numbers can only be contextualized by the type of roaster, type of probe, and positioning.

Do we say a coffee is “in first crack” when I hear the very first pop?

No. There is quite often some early pops that are outliers, and come before the coffee has really reached first crack temperature. I would say coffee is truly in first crack when a regular sound of successive pops is heard. (If a roast is stopped right when the initial sound of first crack is heard, even accounting for some forward “momentum” from the heat stored in the coffee, it will likely taste very grainy and possibly astringent).

If I read “roast coffee through first crack,” does that mean until the very last pop is heard?

My opinion here is also no. Besides semantics, it is also hard to sense when the last sound of first crack has occurred anyway. But there are coffees that, if you are targeting a lighter roast level like City roast, you might be shutting down the heat while you are still hearing the later part of first crack? Why? Because in some cases the roast has some “momentum” in terms of heat, and will coast through the end of first crack. There is also no set understanding about coffee needing to “finish” first crack, or even what that means. Remember, roasting is a process of physical and chemical changes brought on by heat. The crack sounds are related to those changes but don’t signify anything in themselves, except one of the better clues we have to help us anticipate roast flavors.

What does it mean if first crack is rapid?

If you notice first crack sounds rapid, more than usual, their is likely too much heat being applied. A very rapid, violent first crack is, in my opinion, not the best way to roast coffee for quality taste. When you sense first crack is nearing, it’s good to bring down the temperature slightly, if you have heat control), so you enter first crack in a more controlled manner. On our larger roaster, where we usually have first crack at 400-405 f, we often moderate temperature a but at 380 f. , but we are careful not to lower the heat too much or the roast could stall.

What does it mean when there is little or no pause between 1st crack and 2nd crack?

Drum roasts usually have a pause: Air roasts that are rapid can blur first and second crack together in some cases. Really, it can happen with any roast where there is too much heat input and the Rate of Rise (ROR) in bean temperature goes out of control. Coffee changes from being endothermic (taking in heat during first part of the roast …from green to first crack), then switches to being exothermic at first crack, releasing more heat than it absorbs from the environment. That’s why a roast can change rapidly at the end and the ROR is too rapid.

What if my roast stalls during first crack?

In anticipation of first crack you might want to lower the heat so the coffee doesn’t enter first crack in a rapid and uncontrolled way. That’s a good idea generally! But if you drop your heat too much your roast might stall out. In other words the thermal “rate of rise” might flatline or even drop. There might not be enough “thermal momentum” to advance the roast and, once too much energy is lost, it’s hard to get it back. This can result in a long roast, a wonky roast curve, and perhaps a “baked” roast taste. With experience you will learn not to do this, but it can take a few lost batches to learn that.

Should first crack be completely finished before I stop my roast?

If you are aiming for a light roast, generally you do not need to wait until the absolute end of the audible first crack in order to stop the roast. Actually, the answer here is specific to the type of roaster you are using, the coffee batch and the style of roast you are going for.

I like really light roasts, so what is the soonest I can stop the roast process?

Coffee needs to enter first crack or it will have no sweetness in the cup, or a very “grainy” tasting and dry form of sweetness. But depending on the roast process and batch size, you can actually stop the roast cycle while there is still audible cracks occurring. Some say these roasts “finish first crack in the cooling tray” as one Nordic roaster put it. Ultimately, you are roasting to suit your taste. In that light, there is not a “right roast”… there’s just what’s right for you.

How do I get to a Full City roast in relation to the 1st and 2nd crack?

Full City, a roast level on the dark side of “medium roast” means the coffee has gone completely through first crack, and is in some form at the threshold of second crack. On my roaster I usually hear the first snap of second crack at 445 to 448 fahrenheit. For me, Full City is usually around 440 fahrenheit or so. For others Full City might mean they hear that first sound of second crack and then drop the roast into the cooling tray (on a commercial shop roaster). Full City is supposed to mean the full development of roast taste without the burnt notes of a French Roast. So for me that is in the range of 440 to 445 or so. Of course, these temperature measurements and the degree to which a roast continues to progress when the heat source is cut off depends greatly on the type of roaster.

What do you mean by City roast and City+ and what are they in terms of the First Crack?

City roast is a light roast level, and City + is (as you might think) “City roast with a tad more development. On my roaster I start first crack at 405 fahrenheit and it tends to come to an end with most coffees at around 418 f. In this range City roast is what I feel I get at 415 to 420, and City + usually correlates to a peak temperature of 425 to 435 or so.

How do I adjust the roaster temperature to have the best roast curve going into First Crack?

Most coffees on my roaster hit first crack at 404 fahrenheit … sometimes a bit earlier at 400 though. If I feel the roast is progressing at a good clip, with a solid Rate of Rise in temperature and roast reaction rate, I will tend to drop my burner temperature at 380 fahrenheit, 20 degrees shy of first crack. I make sure not to overreact though, as I don’t want the coffee to stall as it goes exothermic in first crack.

I heard that I should roast coffee until the surface color looks smooth and even brown. When does this happen?

Just like some people used to say ” I like coffee when the bean is dark and oily”, others believed a good roast had to do with a smooth surface appearance. Indeed there is a point where the coffee expands enough and the browning reactions have sufficiently completed that the surface no longer seems mottled in color and texture. People used to feel this correlated to a Full City roast. The issue is that different coffees will expand and brown differently, and roasting any coffee until it looks a certain way ignores the fact that how the coffee tastes is the most important thing. Nobody drinks a bitter cup of coffee and says, “I don’t enjoy this terrible brew, but in fact I know it’s good because the beans looked so smooth.”

What is Third Crack?

The quasi mythic third crack supposedly occurs after a harrowing period of silence after second crack ends. Third crack is followed immediately my spontaneous ignition and a call to 911.

42 Responses

  1. I never heard a crack until I ‘graduated’ from the Nesco to the Behmor. Nesco, big step up from buying brown beans. Behmor, another big step. Still barely toddling. Articles like this help a heap. Thanks!

    I’m generally hitting 1st crack about 13-15 minutes in. 2nd after 2-3 more. It says it will handle a pound. I think you need to stay at 1/2 of that. One day, I’ll get around to varying roast temp. A primer on this topic could be useful. Am surprised there isn’t an optimal time range for roasting, in general, with variation by moisture, etc..

    1. Yes I hear what you are saying about the Behmor at actually getting 1 lb roasts done in a reasonable amount of time. I find (at least at home) that pre-heating the Behmor is a necessity to do 1 Lb. roasts, but I usually do 1/2 Lb roasts because that’s all I need. We do have a ton of Behmor info on various roast profiles etc in our Library here … they are collected on this page:

  2. is there any way to get the accurate temp in a Behmor roaster? (older one). As far as I know only the bullet can give accurate temps.

    1. Hi Gary,

      Good question. Do you have the first generation Behmor? On the 1600+ and 2000 models, you have access to thermistors that read chamber temp on the sidewall, as well as at the exhaust. It’s not perfect, but can be helpful in identifying the temperature benchmarks for your machine. Pressing the B button displays chamber temperature, and A button exhaust temperature. It’s important to keep in mind that the chamber temp is not very accurate once the exhaust kicks in at 7:30 into the roast, and I tend to switch over to reading the exhaust temp rather than chamber, though I really go off of time, smell and the sound of 1st/2nd crack more than anything at that point.

      The Behmor probe on the newer 1600+ and 2000 models is located on the right wall when facing the roaster. Part of the reason it’s difficult to get an accurate temp reading is due to the large chamber size, as well as the fan as mentioned above. I’ve seen people add thermocouples that breach the sidewall to get a better internal chamber temp reading, but I’m not really sure if this will increase accuracy because of the combination of chamber size and exhaust fan.

      We sell panel and motor upgrade kits for the earliest 1600 and 1600+/2000 that will allow you to check temp, roast manually, and also comes with an upgraded 2-speed motor. It looks like we’re out of the ones for the 1st generation 1600, but you can see the other HERE. I will reply to your comment shortly with an update on when to expect the 1600 kit if that’s the one you’d need.

      Here’s a link to our “cheat sheet” on the different functions on the upgraded panels that are standard on the new machines – Manual Mode Cheat Sheet.

      You mentioned the Bullet as well in terms of reading bean temperature accurately. It’s worth mentioning that the temps noted for the different roasting stages are actual internal bean temperature, which none of these bean probes and thermocouples can read. The Bullet has an infrared sensor which reads the exterior of the bean, so it’s close. But the important point is that while temperature readings will vary depending on machine, probe placement, type, etc, they help establishing base lines that can be used to track roast changes and communicate with others about profiles. All that said, they are not necessary to get a good roast!

      I should also mention that the Home Barista forum is a good resource for DIY hacks to your machine, but you should know that any modification will void your warranty!


  3. What a great description of the process at different stages.
    Thank you. I am looking forward to meeting you one day in shop and testing one of your specialties.
    I have a question on at what stage does one add the flavors that you say are part of the bean. Are these beans grown in an area with the other contents or is bean washed with a liquid mixture of all of the ingredients listed.?
    I am bringing protected sterilized containers on my coffee for tasting parties .
    As you can imagine each sample may be small since I don’t grind for more than 2-3 cups .
    After tasting we vote on favorite and I will make another cup .
    When will you expect to be open for visits?

    1. Yes I look forward to being fully open again! Especially to have classes, demos, etc. In terms of coffee flavor, these are aroma/flavor attributes intrinsic to the coffee itself. They aren’t imparted in any external way. That’s what is so special. Coffee isn’t like tea (such has jasmine tea literally flavored with jasmine flowers).

      It can seem esoteric, but if you had a tasting party with 1. a wet-hulled Sumatra 2. a dry-process Ethiopia and 3. a wet-process Guatemala , all tasted side by side, you would absolutely experience huge differences in flavors. How would you start to express that in words? It’s tricky because translating those experiences in words can be so different for different people with different palates. I love the fact you do this with others and vote on favorites. You learn a lot by making coffee a social thing – I can’t wait until we return to “normal” – I will have a new appreciation of that aspect.

  4. Thanks, Tom, for this additional guided tour through coffee roasting.
    Re: lowering temperature as coffee “approaches” First Crack.
    Roasting with a Behmor using level P5 manual do you also suggest “slightly” lowering temp as First Crack nears? If so, do you suggest P4 just before First Crack? Then what?
    Do you suggest P3 after First Crack has started? And is the start when just one pop is heard? Or does one wait till 3 pops together are heard?
    I ask this because you describe the Behmor as a “gentle” roast and may respond a bit differently.
    Thanks very much!

    1. You know, I can’t remember doing a Behmor roast with a 1st crack I thought was wildly too fast and out of control. It’s easy in an air roaster. So lowering the temperature just before 1st crack in a Behmor is something I haven’t done. I probably should have made it clear that I feel it’s a “non-issue” with some types of roasters that already have a fairly gentle “Rate of Rise” in terms of temperature. My struggle with Behmor is usually the opposite; to push the heat at the coffee harder, because it’s very gentle as it is…

  5. Thank you for the information. I have a non-related question as to cracking.
    What makes roasted coffee become oily? Frequently it is noticeable just after first cracking, some time in my roaster, some time in my storage can. Is this a bad thing for flavor, quality? (I use a SonoFresco roaster.)
    Thank You

    1. On the oils coming to the surface, the general understanding is that they are driven out by the pressure of gasses formed during roasting. In particular, when you reach second crack the internal structure of the coffee bean becomes fractured, and that allows outgassing more, and pushes the oils outward with it. Outgassing happens during roasting and afterward, so often the oils take time to appear on the surface.

  6. This is the best blog ever written about this topic. I especially appreciate explaining where a roast should be relative to temperature. Thanks.

    1. Thank you ! The temperature thing is tricky but even speaking in “ballpark ranges” can be useful.

  7. Excellent Tom, thanks! I learned. The cracks rule. I tend to use cracks equally with temp to gauge the roast. The part about ending roasts in mid to near-end of first crack was very helpful. I love Ethiopian naturals and I’m going to end some roasts just before first crack ends. I don’t know why, but somehow I’ve thought for years that first crack HAD TO come to a full stop end to hit City roast. I’m roasting on a Quest M3 with a bean probe and drum air probe so I have total control and can easily get a 2-3 minute pause between cracks. My favorite technique on the darker end is to listen for the first tiny crackles that begin with 2nd crack. I can end the roast then (FC+), or wait a little until I hit Vienna roast with an excited rolling 2nd crack. The Quest is quiet and you can open the bean chute and listen to what is going on, almost directly, inside the drum. I have hit 3rd crack once! #stayintheroom lol

    1. Ha ha – yes , stay in the room for sure. A “third crack” roast in the house is something you will live with for a week until the smell dissipates, as I unfortunately know.

      Yes my experience with “finishing first crack” has really changed. What I found was that, especially on air roasters and poppers, if I waited until I was sure first crack completely ended, I always had more of an overlay of roast tastes than I wanted. I was aware that some roasts “coast” to a finish as they cool, especially on a larger batch roaster. But even on a popper I was missing some of the bright notes I wanted. I realize my taste shifted toward preferring lighter roasts over time too, but only when I started ending air roasts when I felt 1st crack had past it’s peak, and was ebbing, did I get lighter roasts that I liked better. And they didn’t taste like grain either…

  8. I have a Gene roaster. Thank goodness it has excellent visibility because that’s the only clue I have to the stage of roasting. It’s a quiet machine, and you would think the cracks would be very audible. After all, I went from a Fresh Roast very loud machine and nevertheless could plainly hear the cracks. I’ve had the Gene for at least three years and am gradually getting better at gauging with only visible clues. I’d switch to the Behmor but would probably set the house on fire trying to get a really dark roast. Is there any machine out there with good visibility and audibility that also can reach a dark roast, past the second crack?

    1. I think you already have the machine with the best visibility: this is why the Gene caffe is used in a lot of “demos” of coffee roasting. But it does have fan sound (though much less than a freshroast for sure!). I think the Behmor, while it is a great roaster, is one of the hardest in terms of visibility. Trying to see the coffee through the glass door and through the mesh drum, with the yellow-ish hue of the roast chamber light … that IS tough! I have found some really good, string LED directional lights though. An LED light makes a world of difference with any roaster. Lately I found these LED ring lights with a clamp (mostly for use with a phone for zoom calls and selfies!) to be really handy for this, and inexpensive.

  9. Very informative but yet complex and in some instances my recorded results a home are not coming close and conflicting with the baseline information provided. Ultimately this is spelling out doom for me starting out on the cheap using the Nostalgia air popper. This article made it clear monitoring the roasting chamber temperature accurately is critical.

    Reviewing my recorded data of 7 roasting sessions my results are bringing into question my ability to obtain accurate temp reading on my air popper. Having completed the “Adding a Dial Face Thermometer” modifications with the thermometer tip about 0.5 inches above the swirling mass of beans, my observed temp results don’t come close.

    Next add on top depending on ambient air temps the air popper’s temp regulator typically is kicking in 1:45 – 3:00 minutes at an indicated 425 deg into the roasting session. Resulting in the air popper’s applied heat begin suspended for about 7-10 seconds lowering the chamber’s temp by an indicated 100 deg. After reading this multiple times, I’m having to questioning my perception/understanding of my roasting results. I’m not getting indicated temps anywhere near provided baseline and am wondering if what I though was beginning of second crack is more likely continuation of a stalled first crack.

    Will have to re-think moving forward or not.

  10. Hi there – I have a Hottop home roaster and first crack for me hits at around 360-365F. This seems quite a bit lower than your 404F, but I do get a nice roast with development time of around 90 seconds and usually finish roast at 380-5 ish.

    1. Hi Greg! That makes a lot of sense actually. Short of an infrared probe, it’s very difficult to get an accurate bean temp reading, so you should expect some variance from one roaster to the next. Most home roaster probes are situated to read the temperature of the air inside the drum, rather than the beans themselves. Temperature readings can vary quite a bit depending on other factors too, probe type, probe location, ambient temp, etc. Once you know what temp reading your roaster displays when hitting the benchmarks, you then have a baseline for subsequent roasting and comparing with others.

      I hope that makes sense!

      Thanks for your question Greg.


  11. Hi Thomas, This was great. I have been a Sweet Marias customer for a while. Artisan even says I have “the curve”… But I have never known what to do with looking at the beans post-roast. I definitely learned something here. Thanks so much! Marc

    1. That’s great – Yes I think a tool like Artisan is great, but there’s always a need to corroborate that data with what you are seeing / hearing / smelling (and of course tasting). I’m glad you found it useful material.

  12. Tom indicated that he had issues with lighting and the beans looking darker in the video than to your eye. You might try using something other what a quite background. A gray sheet would be ideal… photography circles have something called 18% gray. I think you’ll find that the video will more closely match your eye sees.

    Love the video(s)! Tom, you are such a “character” and this makes for a great teaching experience.

    1. Yes! I was actually looking for my 18% gray card and couldn’t find it. Might be time to get a new one, as it must be 30 yrs old!

  13. Great article, thank you! I’ve gone from an air roaster where first and second crack are very clear, to a drum roaster (Gene Cafe), but the noise of the machine makes it too difficult to hear the second crack, in particular. So I rely more on sight and smell, but I know I’m missing something! Thank you for the general ideas around temp settings to ease into first crack…I’m still trying to figure this roaster out.

    1. Yes – the Gene caffe is great for seeing the roast (unlike Behmor etc) but not so great for hearing it. I have been looking at ways to add a thermometer to a gene caffe in the exiting air flow (since I definitely cannot get one into the roasting chamber) as a way to monitor roast level as well.

  14. I just decided to jump into roasting and placed an order for some popcorn poppers and a mess of beans. This article is really helpful in that the thing that gives me the most apprehension about roasting is my ability to determine the cues that tell me where a roast is at. I really appreciate the advice here. Sounds like getting a thermometer when they’re back in stock would be helpful for me, but I hope I am able to gain a feel for roast levels through practice.

    I have always preferred darker roasts for both brewed coffee and espresso, but one of the reasons I decided to do this was to expand my horizons a bit and experiment with different roast levels. Is it easier for beginners to shoot for a specific roast level? Does it matter if I shoot for lighter or darker, or more medium, with my initial roast attempts?

    1. Hey Dan, thanks for the question. Glad to hear you decided to take the plunge, and hope you enjoy roasting!

      I always recommend folks start with the popper. Not only is it a very low entry cost, but with all that visual access to the coffee during roasting, the popper is really one of the more educational roasters to learn on. It can be a little tricky to get a dark roast on a popper, so I’d start with light/medium roasts and go from there. A fairly small roasting capacity also means you’re going to get several tries before you’re out of coffee. There will be plenty of opportunity to adjust roast time depending on how the coffee tastes. Too bright? Roast longer. Too much roast/bittering flavors? Stop your roast earlier.

      Try just roasting the coffee until the first cracks stop (or slow significantly, at least), and then adjust from there. Personally, I wouldn’t fuss with a thermometer until you feel comfortable achieving drinkable results consistently. I don’t think it will be long until you reach that point! Then you can decide if you want to add another variable to monitor during the roasting process.

      I hope that helps. Enjoy your popper, and feel free to reach out with any other questions you have!


  15. Good article. In the end, if you have a good roaster with repeatable thermometry, you will learn to roast to temperature and use the cracks as additional information which is helpful however not determinative in your roast profiling.

    I have never roasted at sea level; in fact all of my roasting has been at about 6000 ft. of elevation, and for the last 10 years, in a Diedrich IR-1. It was nice to see that you count the temperature difference between onset 1st Crack and onset 2nd Crack as being around 45 degrees F. I get the same, or roughly so, however I generally call 375 F. as the temperature at which I consider first crack to have started, pops or not (generally they are present). I terminate my roasts for espresso (all I do and 99% of them are with Ethiopian DP coffees) at around 418.5 F, maybe 419F. I reckon this to be a degree or 2 short of onset 2nd, which I do not want to enter.

    I’m reasonably, but not entirely, certain that the 20+ degree temperature difference that we have when it comes to calling onset First Crack, is due to altitude, but I have no proof of this.

    1. Thanks for the comment Ken. You absolutely do have a good roaster and thermometry, and that’s something many home roasters don’t enjoy I think. Generally a heat system with more mass, better components and good quality temperature sensors is going to yield more consistent results, and it would make a home roasting machine the price of, well, a Diedrich! I think people can do pretty well to mitigate the impact of the variables, but it definitely would be easier with a roast system like yours. That said, even a lot of professional grade roasters don’t get consistency because no matter what you use, getting good roasts takes attention to detail, and care. You can’t believe some of the things of seen over the years… :-/

    1. In the middle of 2nd crack, you will really be at French Roast at that point…

    1. That’s a good suggestion – we should produce an article specifically about roasting robusta. It is different. I would extend the roast time, and make sure it is well developed overall. Super light roast robusta is not usually very good IMO.

  16. Hi,
    This might sound a bit dumb but I roast my coffee in a saucepan and simply stir it until the beans are starting to have a slight sheen and are possibly full city (this is to make Turkish coffee) – which return to a matt colour once the beans have cooled for 24 hours. It takes about 10 to 12 minutes roast. I have tried to understand the difference between the cracks but I still cannot distinguish one from the other. The end result is understandably hit and miss. Is there any advise you can give me?

    1. It sounds like quite a dark roast, and it might be that the cracks are blending together. So some coffee is still in first crack when other coffee is hitting second crack. I have had this myself when roasting in a cast iron skillet, which is why it comes to mind. The only advice I could give would be to lower the heat as the coffee browns, before any sign of a crack, so you slow down the roast more … this along with constant stirring should result in a more controllable roast in the last stages, and more distinct first and second cracks! I hope this helps a little…

  17. I don’t have anything to contribute except to say this is all very useful, including the comments. I need to go back to the basics of roasting from time-to-time, if nothing else to remind myself of the temperature windows and this gave me what I needed. Thank you!

  18. Thanks for this. Not sure about where I end up with what I do. The “cracks” component is a bit an issue when turning up ones hearing aids creates a great sound from the fan. I often hear “a” first crack, not a bunch. I do use the your companies settings for the SB540 and take the fan down a notch at about 3 minutes. I will start to check the temperature as the machine allows for that. Would those temps be accurate? Just plowing through a lot of different beans

    1. Hi Dean, thanks for your comment. It’s pretty common to have a few early snaps before the main event, and I generally mark the start of 1st Crack once there are several cracks in succession. With the 540, I know a lot of people go max heat and fan at the lead, and slowly taper off fan settings until first cracks are underway. You need that high fan setting up front to get the heavy coffee moving. Temp readings can be a little tricky to use since it’s basically reading the air temperature, not the bean bed.

      How are your roasts tasting?

      We have a pretty helpful video for the SR540 here, too.


  19. About first crack.
    As mentioned earlier by Thom: “Coffee needs to enter first crack or it will have no sweetness in the cup”

    My speculation is that that sweetness associated with first crack is from caramelization of the sugars in the bean ,mainly after any sucrose present degrades into fructose and glucose when the sucrose temperature reaches 186 C (367 F), but some other sugars earlier in the process since different sugars caramelize at different temperatures, see here:

    All of the free water in the greens will have already evaporated from the coffee during the drying process. The water/steam that occurs at first crack would seem to be due to degradation of sucrose in to fructose + glucose + water . There’s a great explanation here:

    My take is that when that degradation of sucrose occurs the release of the chemically bonded water from the degradation of sucrose causes super-heated steam to be created which creates the pop. The pressure of steam at 367 F is around 152 psi or 10 atmosphere’s. Pop! ref:

    I don’t think the difference first crack temperatures seen by Thom vs Ken Fox are a result of altitude unless sugars caramelize/degrade at different temperatures at different pressures, OTOH I have no data on the latter one way or tother
    For another data point, I roast in a 5LB RK drum mounted on a BBQ with the bean temperature monitored via an Omega thermocouple transmitter to a laptop then interfaced with Artisan. For my most recent roast, Guatemala San Martin Jilotepeque, first crack occurred at 394 F, before that Chiapas at 392 F, Tarrazu 393 F, and Sumatra 395 F.
    OTOH I may be recording FC start earlier than Thom does.


  20. Hello!
    I found it very INTERESTING this information. dont you have it in spanish?
    I have a micro roaster house in Argentina, I´m about to learn the art of roast coffee but all the people around have a lot of experience and I know this infor will be very helpfull in spanish

    thanks a lot!

    1. Hello! Thank you for your comment. We don’t have info in Spanish or a translation option on the site at the moment. So sorry! For videos, YouTube does a pretty good job of translating. Hopefully that’s something we can address in the future.


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