Playing with dark roast on Ikawa

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Milligan
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#1: Post by Milligan »

It comes as no surprise that the Ikawa is great at light roast coffees. I get great Ethiopian light roasts, some even as light as a 26 on Roast Vision that taste full of fruit and well balanced. It also does medium roast well with some tinkering. I find it takes a bit of dialing in with the specific bean to get a roast to follow a smooth downward RoR. Since the Ikawa can't predict how much heat transfer will change during development and doesn't have any learning mechanism, I have to adjust for temperamental beans during the development phase.

This is all fine and good since the Ikawa is really meant to be a sample roaster and not a profile/production roaster. Recently, family and friends have asked for some darker roasts and at the same time I've had some beans that I wanted to take a bit higher. Full City or even into 2nd crack is more of a profile roaster job but I was curious to see how the Ikawa did. There isn't a lot from Ikawa on darker roasts. I believe there are some settings on the Home that have a darker profile, but nothing for the Pro model (which makes sense for the goal of the roaster.)

The problem going into this is that time scales are usually highly compressed on the typical Ikawa profile, but coffee needs to take its time from 1st crack to 1st crack end and into 2nd crack. Ideally, 3-4 minutes. Drying is usually over in 2.5mins and Maillard can be stretched however much I wanted. I wanted time scale to somewhat match other roasters so I decided to base my profile off of Ikawa's Espresso Roast profile, but stretched even more.

The first coffee is a Guatamala Finca Santa Margarita that I got from CBC. I used it because I have never been happy with it at a lighter roast so I thought it would be a good candidate to start.



Don't pay attention to the CC or 1 crack lines. Those are wrong. Some update along the way broke the way I can adjust those during the roast so they are stuck wherever I ended up pushing the button. Typically I hit first crack around 395F on a typical fast Ikawa profile. With the espresso roast profile it usually hits later at around 410F on the exhaust temp. I've found that larger delta between intake and exhaust then 1st crack is at a lower exhaust temperature. So the lazy increase in exhaust temp here with the lower intake/exhaust delta is causing first crack to take place at a higher exhaust temperature. Likely around 410-415F before a rolling first crack takes place. This would be around 7:30 and coincides with the tiny in the ROR. This gives me around a 3 min dev time on this roast in total.

My next issue is knowing what temp the Ikawa gets into second crack. The "rule of thumb" is around 30-40F increase after 1st crack. So I had the profile ease into 450F exhaust temp. Sure enough I hit 2nd crack around 10:30 and dropped just a few seconds after.

Roast vision showed an 9 which coincides with a 46 on Agtron gourmet. Just past Full City, which lines up with barely getting into second crack.

I let it rest a day and tried it. This isn't the roast level I personally enjoy. Perhaps it is PTSD from horribly dark Petes that lingers on the tongue for hours, but I wasn't jazzed about trying it... It actually wasn't bad. Low acidity, heavy body, slight bitterness that wasn't unpleasant, and no smokey flavor. What surprised me was how clean it was compared to darker roasts I've had in the past. I tried a second cup the way a lot of my family would have it, with a dash of sugar and cream. Quite enjoyable actually. Certainly something I could enjoy on occasion.

Next up I have a Sumatra Mandheling from Happy Mug. They suggest roasting 40s into second crack, which seems like quite a bit. It also doesn't tell me much about temperature rise after second. I don't know anything about what the RoR should do in darker roasts. Perhaps stalling out is preferred to get a bit more time but not the temp increase during rolling second? That was my thought anyway.



So this roast was similar to the last but I extended the time to 11 mins and reduced the slope leading into 450F finish temp. Again, ignore the CC and 1st crack lines for the most part. It acted like the last but the Ikawa had a little harder time controlling the RoR on this one. 1st crack started around the 410F mark like the last time. Second crack started a little earlier at around 10:20 and I went until second was rolling dropping early at 10:50. 30s or so in 2nd crack with a gentle rise in temp.

This one hit a 7 on roast vision which is roughly a 40 Agtron gourmet, a Vienna roast with a few tiny spots of oil appearing after a day of rest.

The Sumatra really surprised me. Right when I opened the lid on the jar after resting I got a very pleasant spice aroma. Ground aroma was earthy with dark spices. Wet aroma was interesting reminding me of holiday spices like a mix of cinnamon, nutmeg, cloves, and perhaps anise. The taste was very sweet, no acid, full body, very mild bitterness on aftertaste, with a mild earthy/spice flavor. The body and sweetness is what was the most pleasant part. I can see going a little lighter to further reduce bitterness and then add a medium natural to give it some complexity and this could be a great roast.

I plan to do a few more and mark them a bit better. Unfortunately Ikawa doesn't have an option to mark 2nd crack so it is a bit harder to log these roasts. It is also VERY hard to identify second crack over the high pitched fan. It is recognizable but not without an ear to the machine.

One last observation is that there is zero smoke aroma or taste and very little "roasty" taste compared to the roast level. Perhaps this is due to nearly 100% convection roast and smoke not building up in the roast chamber. Much different taste than the normal dark roast that is sold commercially.

I have a Mexican La Laja that I roasted but still need to cup and will be doing a Guatemala Huehuetenango to just 2nd crack, supposedly it is a chocolate bomb. I also have Happy Mug's espresso blend that they recommend to take to second crack.

Anyway, hope some of that was at least interesting. I know we mostly talk about light and medium roast so maybe this could be a place to discuss some darker roast styles. Any tips as I figure this out would be much appreciated.

GDM528
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#2: Post by GDM528 »

Thank you for the post, and welcome to the dark side! I've been pretty much fixated on Full City roasts with the Ikawa, as posted in another thread: IKAWA Home - profiles - yes, it's largely for the Ikawa Home, which is sorta like the Pro, but with a broken ET thermocouple and set to inlet control. Both are aggro fluid bed roasters seemingly targeted to pour-over enthusiasts, such that most roast profiles are in the seven-minute range. Refreshing to see your profiles hitting the eleven-minute mark.

I can corroborate your observations and offer a few more:

I've observed the 'burnt-for-no-good-reason' tasting notes get really noticeable (to me) when ET hits 455F, so you're getting close.

It takes my roasts five days to 'juice out'. immediately post-roast all beans look dry. 12-24 hours later 10-20% show light oil spots, and by day five everybody is shiny. I've had to learn to trust the temperatures over what I see or hear. I've observed the thermal shift associated with first crack chemistry roughly 30 seconds ahead of any actual sounds.

If you switch to inlet control, you can program crazy-fast temperature steps, which can be used to isolate the different phases of the roast. I've been doing this to figure out how much time to spend in each phase so I can translate those findings back into a more sensible looking roast profile. I've also used this technique to add dark-roast notes to an otherwise light/medium roast, and the tasting notes are... interesting.

Milligan (original poster)
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#3: Post by Milligan (original poster) »

GDM528 wrote:Refreshing to see your profiles hitting the eleven-minute mark.

I can corroborate your observations and offer a few more:

I've observed the 'burnt-for-no-good-reason' tasting notes get really noticeable (to me) when ET hits 455F, so you're getting close.

It takes my roasts five days to 'juice out'. immediately post-roast all beans look dry. 12-24 hours later 10-20% show light oil spots, and by day five everybody is shiny. I've had to learn to trust the temperatures over what I see or hear. I've observed the thermal shift associated with first crack chemistry roughly 30 seconds ahead of any actual sounds.

If you switch to inlet control, you can program crazy-fast temperature steps, which can be used to isolate the different phases of the roast. I've been doing this to figure out how much time to spend in each phase so I can translate those findings back into a more sensible looking roast profile. I've also used this technique to add dark-roast notes to an otherwise light/medium roast, and the tasting notes are... interesting.
Yes, I thought it would be nice to get a longer profile but I have been working on shortening it a bit as I refine the profiles. Since the Ikawa dries 3x faster than a drum roaster without scorching the beans I could cut a few mins off for beans that can take that such as SHG or dense beans. I do like how the espresso profile eases into heat so 1st crack comes slowly. I've found with a lot of the fast profiles that 1st crack is usually done within 45s-1min where with the longer espresso profile it is extended to 1:30 or beyond which I think these darker roasts need.

I did another round of dark roasts a couple days ago and struggled to hear 2nd crack on most of them. With only 90g cracking and the fan making quite some noise it is hard to hear. I can see a drum roaster being much better for this. As far as I can tell there isn't an obvious dip in RoR as 2nd crack hits so I don't have a way of analyzing the temperatures to figure out where 2nd crack started.

I like the idea of inlet control because it would make it easier to smooth out the 1st crack dip. I may have to mess with that a bit more once I get a profile I like.

I did a Guatemala Huehuetenango to just 2nd crack (12 roast vision) and it is very nice. The Sumatra did not turn out great. I think I went too dark so I redid that one with and end temp of 440F and have yet to cup it.

GDM528
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#4: Post by GDM528 »

Lots of differences between an Ikawa and a drum roaster, but one difference this thread has got me thinking about is the cool-down process. In a drum roaster, at the end of the roast the beans are dropped and cooled in just a couple seconds. On the other hand, the Ikawa will keep the roast in the chamber for a full minute before allowing them to be ejected - yes, the air isn't heated anymore, but it's still picking up a fair bit of latent heat from the machine structure, such that the area under the ET curve during cooling is in the ballpark of the last 30 seconds of the heated roast. Yes, that's a gross oversimplification, but I still suspect net development time is a bit longer than what the profile says it is, especially when the ending temperature is really high.

There's a subtle dip in your RoR right around first crack, and I suspect it inflects a bit prior to when you hear the beans starting to crack. With a probe inserted directly into the spinning bean mass, I've been able to measure what looks like a transition from endothermic to exothermic around 15 seconds before any audible cracking sounds - but more importantly, at the same 410F temperature that you've observed. Whatever causes that first bean to crack may not be representative of the remaining 99% of the beans. The Ikawa (especially on inlet-control) is so crazy-precise and repeatable, it's left me feeling that listening for cracks is an old-school technique, now that science and technology has gentrified the process.

I've observed some of Ikawa's curated dark roast profiles for the Home machine vary development time from about 1.5 to about 3 minutes. For light roasts they stop at 2 minutes. Does that mean the guidelines for avoiding a 'baked' roast are different when going dark?

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Peppersass
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#5: Post by Peppersass »

I think you may be right about the beans continuing to develop during cool-down, though bear in mind that the exhaust temperature drops very quickly, It could be that the beans in direct contact with metal, which is far from all of them, may stay a little hotter. At any rate, I try to get the finished beans out into a tray outside the roaster as quickly as I can.

With the Ikawa V3 Pro, as long as the profile is the same, I've found that the most reliable indicator of final bean color and development is drop temperature. Once I figure out the drop temperature, I can consistently get the same product roast after roast without giving any consideration to dry time or the beginning of 1C (even though I mark them.) But how to determine the drop temperature?

The first time I roast a new bean, I mark 1C when I hear the first pop. Then I look for a minimum rise of 10 degrees for a light roast. If the color meter says I got a very light or light medium roast, I'll try again until I get a light roast. Once I get a light roast confirmed by the color meter, I'll do the next roast at 3-5 degrees higher drop temp for a light-medium roast. If that confirms on the color meter, I'll do a third roast 3-5 degrees higher for a medium roast. Once the beans have rested, I'll taste them as espresso and decide which degree of roast -- i.e., drop temperature -- brings out the origin flavors best.

GDM528
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#6: Post by GDM528 »

Peppersass wrote: The first time I roast a new bean, I mark 1C when I hear the first pop. Then I look for a minimum rise of 10 degrees for a light roast.
What's your typical ET when you mark 1C? With my Home model, it's about 250C/480F inlet temp and about 210C/410F ET/BT.

Likewise, is that a 10 degree rise Fahrenheit? Those beans might still sprout if you planted them ;)

So, you can dial in a roast in three passes, using fewer total greens than the minimum single-batch size of a drum roaster - kudos!

Re: origin flavors, I have cognitive dissonance about the effect roasting level has on the source material. I hear the logic that says lighter roast levels retain the "origin character" of the greens - but that character is lost by the time you reach second crack. Despite that, the OP and many other dark roasters clearly describe flavor differences between various origins. How can this be?

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Peppersass
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#7: Post by Peppersass »

ET at 1C varies with the bean. I've seen (heard) it as early as 396F and as late as 410F.

Yes, initially I look for a minimum 10F rise from the 1C temp.

I think with any roaster it's hard to decide when 1C starts. Some beans crack vigorously and with some I might hear one or two pops or none at all. Those quiet ones are popping, just not loudly enough to hear over the relatively quiet fan of my roaster and the range good fan I use. With my Quest M3, I used to wait until 1C got going (i.e., not when the first pop or two occurred.) When I first got the Ikawa Pro V3, I found it was best to mark 1C at the very first pop. If I don't hear anything, I'll typically mark at 405F for that first roast and adjust from there. I wouldn't be surprised if my Quest roasts would have benefited from that approach (different 1C temp range, though.) Rao has an article about marking 1C too late, where he uses a slight dip or spike (can't remember which) in RoR to mark it. I tried that with the Ikawa, but the scale used by the app doesn't provide enough resolution for RoR.

As for origin flavors in dark roasts, I personally haven't tasted them, but I wouldn't be surprised if some of them come through for some beans and for some people, but likely in a more muted fashion and potentially subordinate to roasty flavors. Probably depends on the taster. It could also depend on the brew method, too. I think it's more likely to taste origin flavors in a dark roast with pourover rather than espresso. For me, dark roasts pulled as espresso are dominated by chocolate and nuts, and sometimes unpleasant roast flavor. They can be bitter, too, though a good barista can eliminate or minimize that (e.g., updose and pull Ristretto.) I like light roasts not only for the more prominent origin flavors but for the brightness that comes for a more acidic taste profile. I get all the comfort food experience I need from the milk and natural sugar in my skinny cappas.

Milligan (original poster)
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#8: Post by Milligan (original poster) »

I agree with marking 1C at the first pop. The audible indicator of 1C seems to happen either right when RoR changes a bit or right after. Whenever I wait for several pops close together I'm usually 10 seconds or more past the slight dip or change in RoR. As I've noted before, it also seems that 1C happens at a later temperature on average when I do a quick profile compared to a slow profile. Quick profiles may have me at 398-400F while slow profiles push me into the 400-408F range.

My big questions I'd love to edge closering to understanding for darker roasts are:
  • How much development time vs temperature rise do people shoot for when going dark?
  • Do roasters still try to draw out 1C when knowing they are going to 2C? Seems like it is hard to balance getting good 1C development while still having the momentum to get to 2C.
  • Are there any visual indictors on the graph of 2C? Or at least for me, figuring out the rough temperature where 2nd crack occurs on the Ikawa that I can target for pre and post 2C development while making a profile.
I think these fundamental questions will help me better plan a roast into darker territory.

As for origin flavors, I can't say the flavors that show up so prominently and uniquely in a light and medium exist in the dark, but they different origins do have different tastes. The Sumatran had a deeper spice smell compared to the Huehuetenango which leaned more "coffee" flavor. I'm sure as you go deep into 2nd crack everything starts to fade out.

GDM528
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#9: Post by GDM528 »

This thread has inspired me to try the 'long dark':

Ikawa Home: Insta-ramp to 170C/340F inlet, followed by a linear ramp to 230C/446F inlet. ET/BT at 'drop' 10 minutes was 232C/450F, and the beans came out with about 10% showing light oil spots after 24 hours - I expect they'll all be lightly shiny by mid-next week.

Slowly approaching first crack significantly lowered the temperature threshold. In an 8-minute roast I might hear first-crack at 212C/414F - but in this 10-minute roast I heard first-crack at 207C/405F, and observed a thermal 'bump' at 204C/400F - about 45 seconds before any audible cracking sounds. I pushed finish time to the right, which caused first-crack to move to the left... Net effect is this blindsided me into a much longer development time than intended, oops.

Based on audible cracks, temperature rise after 1C was 25C/45F. Between that and the drop temp, seems like enough to have hit second crack - but no, the roast looks like a pretty solid Full CIty. <insert advice to get a Roast Vision here> My only guess is the roast wasn't above the 2C threshold long enough, barely a minute.

Key takeaway for me, is it's not just target temperatures, but also the cumulative heat input leading up to it. Just moving the timing of my setpoints to play with development time is too oversimplified (reaction rates, Arrhenius equation, blah, blah, blah). Longer times = lower temps, which could be a pathway to dark-but-not-burnt. Alas, the Ikawa Home app limits maximum roast time to 12 minutes - is that the case for the Pros too? Dunno if the limit is for the sake of the machine, or for the sake of my roasts...

The thermal bump I observed prior to audible 1C was very-very subtle, and I saw no hint in the thermal data that I was approaching 2C. Is there even an endothermic/exothermic shift during 2C?

Milligan (original poster)
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#10: Post by Milligan (original poster) »

GDM528 wrote:This thread has inspired me to try the 'long dark':

Ikawa Home: Insta-ramp to 170C/340F inlet, followed by a linear ramp to 230C/446F inlet. ET/BT at 'drop' 10 minutes was 232C/450F, and the beans came out with about 10% showing light oil spots after 24 hours - I expect they'll all be lightly shiny by mid-next week.

Slowly approaching first crack significantly lowered the temperature threshold. In an 8-minute roast I might hear first-crack at 212C/414F - but in this 10-minute roast I heard first-crack at 207C/405F, and observed a thermal 'bump' at 204C/400F - about 45 seconds before any audible cracking sounds. I pushed finish time to the right, which caused first-crack to move to the left... Net effect is this blindsided me into a much longer development time than intended, oops.

Based on audible cracks, temperature rise after 1C was 25C/45F. Between that and the drop temp, seems like enough to have hit second crack - but no, the roast looks like a pretty solid Full CIty. <insert advice to get a Roast Vision here> My only guess is the roast wasn't above the 2C threshold long enough, barely a minute.

Key takeaway for me, is it's not just target temperatures, but also the cumulative heat input leading up to it. Just moving the timing of my setpoints to play with development time is too oversimplified (reaction rates, Arrhenius equation, blah, blah, blah). Longer times = lower temps, which could be a pathway to dark-but-not-burnt. Alas, the Ikawa Home app limits maximum roast time to 12 minutes - is that the case for the Pros too? Dunno if the limit is for the sake of the machine, or for the sake of my roasts...

The thermal bump I observed prior to audible 1C was very-very subtle, and I saw no hint in the thermal data that I was approaching 2C. Is there even an endothermic/exothermic shift during 2C?
There used to be a educational set of profiles from Ikawa that demonstrated getting to the same agtron color through a quick roast with higher temp vs a slower roast with a lower temp. You can still find the longer portion on their site under the general profiles called Morten Munchow https://www.ikawacoffee.com/pro-sample- ... rofiles/#!. Unfortunately, Ikawa seems to have removed the fast profile.

I found it very, very hard to hear second crack on the Ikawa. I remember the sound vividly from my Behmor days, I could hear it easily on it. Little sharp crackling sounds. They are higher pitched so I think they get lost in the turbine noise. I did barely make them out on one of my roasts so I know I hit second crack but I couldn't confidently log the beginning of second crack like I can 1C. I can usually hear 1C from across the room. I think I'll have to become more familiar with how agtron/roastvision numbers align to traditional 2nd crack development instead of relying on the sounds.


Coffee Roaster's Handbook by Len Brault p93

I was looking through some of my coffee texts and came across this graph that provides some insight into what a typical curve should look like when targeting a 2nd crack development. This book is targeted toward drum roasting so that should be considered. It looks like RoR should be near 0 during second crack development. It is pretty much a stall out. This does make sense when combined with the following quote in the book:
Coffee Roaster's Handbook by Len Brault p100 wrote:The roast does not enter the next defined stage until second crack begins and is sustained for at least 30s. When the core of the bean begins to reach the same temperature as the outer bean, the smaller pockets of water vapor within the core begin to steam, causing second crack to occur. The beans will further expand in size. While first crack is generally characterized by loud distinct pops, second crack is often quiet, sounding like milk being poured on crisped rice cereal---a lot of small crackling sounds.


"The core of the bean begins to reach the same temperature as the outer bean" That says quite a bit there, which is why the roast needs to slow down so the outside is not scorched before the inside can catch up. A bit later he defines a dark roast (vienna) to start at around 445F-455F bean temp. So that is right where we are at 450F and may be why I never could hear 2nd crack at my lower profile of 440F. What goes against everything I've learned about roasting is to "let it ride", so to say, at a constant temperature for awhile. He says 2nd crack generally continues for 2-3 minutes at that stall temperature before dropping. He goes on to talk about French and Italian roast, but I don't think I'd go that far in the Ikawa. Those are in the 460-470F range.

He also gave a rough target of 2nd crack typically begins 2 minutes after the end of first crack.

Anyway, I thought that was something to mull over while developing my next roasts.