Hello, I thought I'd start this thread as I continue my roasting journey. I've got a dimmer modded gene cafe. My coffee preferences for now tend to be natural, fruity coffees and often use them for milk drinks, so really strong flavours prevail. I'm getting there with the roasting, had some pretty good Yirgacheffe and rocko mountain roasts, but struggled with scorching. So to the question for the experts. I'm finding the scorching occurs after first crack, but interestingly this happens around 215c. This surprises me given most guides suggest final temps from the gene cafe of around 230-235. If I had run that on my roaster, I'd have charcoal. Could this be a machine specific issue? Or are most of the guides suggesting too high a temp for natural coffees? Thanks!

> @"Dan"#p64628 I’m getting there with the roasting, had some pretty good Yirgacheffe and rocko mountain roasts, but struggled with scorching. May not be helpful but is the scorching on these beans you mentioned? Ethiopian and Kenyan beans appear to roast darker due to the sucrose levels in the beans (especially Heirloom and Bourbon) grown at those elevations. The sugars effectively burn on the surface. Again probably not helpful as it’s a totally different roaster but here’s what I use for Natural Heirloom Ethiopian light roasts: [URL=https://i.imgur.com/5l5dCeF.jpeg][IMG]https://i.imgur.com/5l5dCeF.jpeg[/IMG][/URL]

Frustratingly, I seem to be getting scorching with most beans I roast. I'm improving, but it's still an issue. These are two examples, where I progressively drop the wattage from beginning of maillard to the end. But still have issues. Colombian natural castillo. Maxed out at 214c in a 14 minute roast. I think this just had too long after 1c and got too dark. I've been recommended to keep the bean temp below 205 so I perhaps just went too long. [URL=https://i.imgur.com/LdtqrhD.jpeg][IMG]https://i.imgur.com/LdtqrhD.jpeg[/IMG][/URL] Yirgacheffe maxed out at 216 on a 13 minute roast. Could the veiny scorching be burnt on chaff? [URL=https://i.imgur.com/ULodh29.jpeg][IMG]https://i.imgur.com/ULodh29.jpeg[/IMG][/URL]

@"Dan"#p64639 The Yirgacheffe looks fine in colour to me, what I’d expect from that bean at that temp. Slightly uneven but I know it’s hard to get a decent photo to properly show even-ness. I’m not familiar with the roaster but can you get an Artisan graph or similar? How fast are you getting to peak temp? Naturals tend to benefit from a slower rise with longer drying time. You mention dropping the temp at the Maillard point so I’m guessing you’re reaching peak temperature before that?

Sorry yes, reducing the wattage reduces the rate of temp rise, rather than lowering the temp absolutely. Sadly no artisan though… As an example, it took: 7:30 to get from 89c to 207c (to maillard), 2:55 to go from 207c to 212c (to 1c) and then 2:30 to go from 212c to 214c (to end)

I do think the Yirgacheffe looks pretty good. Does it taste ok? The only thing I’d maybe try is a sharper RoR and slightly shorter development time. But again, it looks pretty good to me. Someone with the same roaster might be able to help more.

Thanks! Its the veiny burn which has me a little confused (it's just about visible in the photo if zoomed in) . I roasted today, so will test in a few days.

Funnily enough I roasted some yirgacheffe heirloom natural this evening. It does tend to roast darker in my experience as well. This was on bocaboca roaster. I don’t think the photo shows it well but the vein is on the darker side as well. [URL=https://i.imgur.com/lYUFKjb.jpeg][IMG]https://i.imgur.com/lYUFKjb.jpeg[/IMG][/URL] [URL=https://i.imgur.com/t6HVulJ.jpeg][IMG]https://i.imgur.com/t6HVulJ.jpeg[/IMG][/URL]

Another good way to check for actual scorching is with a UV light, tipping and scorching becomes much easier to spot under a UV-A blacklight if you have one (eye protection recommended)

@"Dan"#p64642 How clear do you hear the first crack? Wondering if the beans actually reach FC. I’ve got a gene with a dimmer too. But FC starts at higher temperatures. You can guide yourself by the amount of smoke also. how many grams do you put in and how many do you get out? I’m curious how exactly are you using the dimmer. Is it based on power consumption? If so, at what wattages are you using it? I’m using it at around 1150W - 1200W. But can be lower in the drying phase or after FC. To have the beens develop longer without getting too dark. I can see starting temperature is 89. I suppose you preheat the machine. For how long? I usually preheat til 230-240C and it takes about 10 minutes. Charging the beans drops the temperature to around 150C.

I'm pretty confident I hear first crack, but will admit it I remark it on occasion if I feel I noted it too early initially. The coffee tastes sufficiently developed to have passed first crack though. I dont get much of the grassy, bready flavours that characterise an underdeveloped roast. I'm terms of wattage, I usually have about 1235W with the dimmer switched off and drop the wattage at 20W increments to control the temperature rise. I don't use specific watts as a guide given different ambient temperatures, but instead watch how the exhaust temp rises on the machine. I aim to have roast times as follows --50% drying phase, 25% maillard and 25% development period for the roasts. I usually aim to avoid 2c in part due to the scorching issue. This means a really slow ror after 1c. I would love feedback on whether that is a good approach for a medium roast! And would be interested in how others go about it. Finally in terms of charge temp, I use the stop function on the gene cafe rather than estop. The stop function ends the cool down cycle at 100c, so depending on how speedy I can be, the 250g of beans go in at around 85-90. The final cool down cycle goes all the way to the bottom to avoid heater damage. I'd be interested in views on the above the wealth of info out there on these machines seems to miss a bit on dimmer profiles, so views on the topic would be interesting! I've just bought 5kg of a this [Natural castillo](https://micro.greencoffeecollective.com/products/wilton-benitez-castillo-regional?_pos=3&_fid=75d31be5d&_ss=c), so will be testing profiles going forwards.

Gene cafe reflections and questions

Doram

Dan So to the question for the experts. I’m finding the scorching occurs after first crack, but interestingly this happens around 215c. This surprises me given most guides suggest final temps from the gene cafe of around 230-235. If I had run that on my roaster, I’d have charcoal. Could this be a machine specific issue? Or are most of the guides suggesting too high a temp for natural coffees?

I’m a fellow Gene with dimmer mode user. The temp you see on the Gene display is from the output probe. On mine, If that got to 230-235 I would probably have charcoal, if not a fire.

The trick to avoid scorching, in my opinion, is to be attentive to first crack and reduce the intensity of the heat with the dimmer as soon as it starts (i.e. when you hear the first pop, not when you have a rolling pop/cracking party). Once you learn to anticipate that (colour, temp reading, smell), you will be able to switch to dimmer mode and start to reduce the intensity slightly even before the first crack starts if you want to, without stalling the roast and baking the coffee.

For me it was helpful to think of the beans the same way as you make popcorn in a pan: as soon as you hear the first pop you need to significantly reduce the heat, or you will burn the popcorn. At this stage there is a lot of heat stored in the corn/beans + the vessel they’re in. They are very close to popping, and you need to pump in far less energy to keep the popping rolling. If once the first crack starts you keep pumping in high heat - you scorch the beans (or burn the popcorn).

Dan

Doram

Thanks Doram, yes completely agree with your approach. The other point I’m learning is that stalling out the temp of the exhaust probe (i.e. Keeping the gene cafe temp stable to say 214) doesn’t necessarily stall the rate of rise of the beans themselves, as long as the exhaust temp is above bean temp, the bean temp will continue to rise.

Great to hear you also don’t go near 235.

Dan

Platypus

😂 I agree with your assessment that’s its rather toad like.

Prezes, your roast looks great, how far beyond 1c did you run it and what sort of temperature for the beans were you looking at?

oddbean

@Doram that’s very interesting. So from what you are saying, you have the machine on full power until first crack(or slightly before that) than lower the intensity. Do you use a meter to measure the power the heater draws? If so how much do you lower the intensity? Are you using a 240v heater?

Doram

oddbean @Doram that’s very interesting. So from what you are saying, you have the machine on full power until first crack(or slightly before that) than lower the intensity.

Correct.

oddbean Do you use a meter to measure the power the heater draws? If so how much do you lower the intensity? Are you using a 240v heater?

My heater is 240v. I don’t use a meter to measure the power, I do it by feel (conditions vary anyway, for example ambient temp or the bean used).

When I just started with the dimmer, I attempted to use it to keep the temp stable once the FC started (i.e. to stop the temp from climbing up, but not letting it fall either). This required a very minimal reduction of intensity - less than a quarter of a turn on my dimmer (full power is 12 o’clock, and I would probably take it down to around 9-10). However, This still produced some scorching and occasionally a darker roast than I was aiming for. So then I started dropping the intensity further (to around 7-8 o’clock). This lets the temp on the display drop a tad, but it doesn’t stall the FC so I still get it nice and rolling (I’m still pumping in heat, only it’s less intence so I’m slowing things down, making everything more gentle and controllable, [more forgiving if you like], with no scorching). I think it’s exactly the same idea as popping corn on a stovetop.

Doram

Dan The other point I’m learning is that stalling out the temp of the exhaust probe (i.e. Keeping the gene cafe temp stable to say 214) doesn’t necessarily stall the rate of rise of the beans themselves, as long as the exhaust temp is above bean temp, the bean temp will continue to rise.

See my reply to @oddbean above. I think this point is key: I initially tried to use the dimmer to keep the temp stable once FC started, but then learned that this actually leads to scorching and less control. I get better results by reducing the heat further and letting the exhaust temp prove drop a little just after FC starts. This way I don’t stall FC but get more control, no scorching and better roasts overall.

Dan

Doram Interesting! Will give it a go on the next roast.

What sort of temps does it show on the gene for first crack?

Doram

Dan What sort of temps do you reach for first crack?

It varies by bean, and also depends on the cleanliness of the probe (after I cleaned it, it registered higher temps). I don’t know if it would be useful to compare numbers from different machines with different beans. I just keep my eyes, ears and nose open and take it from there. I only look at the numbers as a very general reference and to gauge the relative direction of temp within a roast, but don’t think it’s too useful as a target for other roasts (but that’s just me, YMMV).

InfamousTuba

Dan That veiny or wrinkly pattern on the beans isn’t scorching, it happens with high altitude, dense beans that are roasted light (Ethiopians, pink bourbons and Kenyan peaberries are quite susceptible) it can also mean there is unevenness in the roasting. Here is an example of a ultra light roast I bought that has similar features:

Scorching is burn marks usually on the flat face of the bean, it is generally caused by too high of a charge temperature or too low of an rpm in drum roasters, the beans touch the hot drum for too long causing burn marks to appear. Here is a picture of a scorched bean with the scorch mark highlighted as an example:

Dan

InfamousTuba

Super helpful, thanks! I was a little confused about the veininous. Any idea what it is exactly? Could it be chaff getting roasted on?

The Castillo on the other hand seems quite challenging to roast, it can all go wrong very quickly after 1st crack.

InfamousTuba

Dan Super helpful, thanks! I was a little confused about the veininous. Any idea what it is exactly? Could it be chaff getting roasted on?

It is partly due to the processing (washed coffees), varietal coupled with the altitude and the lightness of the roast. If you were to develop the coffee further, getting closer to the start of second crack most of the wrinkles will end up disappearing.

I am not 100% on the exact mechanics of the wrinkling but I try and find out from someone at work

Dan

InfamousTuba

Thanks! Really interesting, perhaps something to do with uneven expansion of the bean?

InfamousTuba

Dan

I think that might be part of what is causing it

For the extended fermentation castillo I am not familiar with the genecafe as far as roasting on it, but most coffees that are extended fermentation need very gentle gas from about the last minute or so before first crack. The RoR will tend to shoot up as the beans start cracking so if the gas is not down very low as you approach first crack you will end up the RoR shooting up and the outside of the beans burning before you can develop the inside at all.

I also prefer faster roasts with short development times for highly processed coffees, longer developments can increase the funkiness of the coffee which i usually want to reduce

Dan

InfamousTuba

Super useful insight. I’ve noted it roasts really evenly up to 1c and very consistently too. It goes wrong after that, so will drop the heat levels considerably to address.

On another note, I roasted a Costa Rica Doga Natural Process from pennine that is a little nuts. Development time was just under a third of the roast, so I suspect it emphasised the funkiness of the coffee.

I don’t think I’m getting the tasting notes from their description. More marmite, soy sauce and a hint of farm yard. A fun coffee, but not one for every day.

DavecUK

Just a few things as I have read entirely through this very long thread.

What weight of beans are you roasting
what chaff collector are you using
Do you have a vent tube attached, of so, how long it is
how old is the gene, I ask in case the chaff collector needs cleaning

few general things.

The roaster has a temperature gradient across it, so when you start exhaust temp may be low, but the side near where the heat goes into the chamber is really hot. often the precursor to guarantee scorching happens near the beginning of the roast…but only shows later.

Don’t roast on full power to bring the temp up, unless it’s midwinter. In a warm room, or outside not, you want to be limiting the power to 1150W max. Don’t worry about the roast taking longer, getting to that first 130C point doesn’t really contribute to “baking” the roast. If I remember rightly after the dimmer mod, I am not sure I ever got to much above 210 ish for roasts.

use your eyes and senses and don’t rely too much on temps you read on the web, it’s for different roasters. Don’t try and do ultra fast 1st cracks, anything you read on the world roasting championship site is not applicable to the Gene…or any roaster for that matter. It’s mostly rubbish.

Use a 250g charge on the Gene not it’s max 300g and watch for chaffy coffees. Try to keep roast times to less than 15m for med to med dark roasting. With light roasts, avoid ultra short times, as you don’t get proper bean development/flavour development. Sure it will be a little shorter than a medium roast, but not by very much at all, you need to stretch the roast with slightly lower power to keep the time similar.

Dan

Thanks Dave, in response to your questions:

I use 250g weight

The chaff collector is the standard large one

I recently cleaned the chaff collector, but just used water, so definitely didn’t get everything out of it.

The ducting I use is 2m at its max. I understand anything longer leads to problems due to the fan on the machine not being strong enough. Therefore affecting air flow.

The model is second hand, but from 2021 according to the label.

That’s interesting about the the temperature gradient, I hadn’t considered the need to limit the ror early on.

As many have now said, it’s clear that this machine beyond many others requires roasting by feel, given the stats provided don’t provide as much insight as one might want. Having said that, managing to roast by feel takes time so having some signposts for newbies is helpful. Given the variability in all measures I suppose the most consistent signpost is likely to be time in each stage of the roast?

If so, here are a few generalities I’ve collected so far, as well as taking advice from this thread. Disagree if any of this is wrong and to emphasise, these are ball parks that will change significantly depending on the bean or if you are trying something beyond the basics.

Keep full roast times between 11-15 minutes
At warmish ambient temperatures, don’t use max wattage at any point.
E stopping can damage the heating element.
The cool down cycle is sufficiently fast to not impact flavour significantly.

Phases for a medium roast

Drying phase - 40-60%, too long leads to baking? Ensure not max temp to avoid scorching later on.

Maillard phase - 20-30% - longer for more perceived sweetness(?)

Development phase (post 1c) 10-30% - longer creates more traditional coffee flavours, but reduces some of the single origin flavours. Longer also increases funkiness in more processed coffees.

DavecUK

Dan Split the chaff collector and clean between the “plates with holes”. 2m is too long for the air outlet pipe really and will affect air flow. I used to use an adaptor and go into 100mm ducting and I never went beyond 33-4 feet and with no sharp bends.

Dan

So I’ve roasted another few batches and realise I’m roasting light, but enjoying the flavours as they come out.

Unfortunately the Castillo I bought five kilos of is not quite to my liking. The tasting notes on the website are milk chocolate, praline and raspberry. I was attracted to the raspberry notes, but instead get praline / custard cream and roasted cooking apples. It’s not bad as a V60, but the milk drinks (my main drink) comes out far too rich and the apples and sweet milk are an odd pairing.

My general sense is buying the 2 kg is my sweet spot of being able to dial in the roast, while not over committing to a bean I don’t know well.

My question is whether the same bean from two different harvests will have a significantly different flavour profile. If it does, I don’t quite see how I could ever buy in bulk, or how anyone does!

oddbean

There are too many factors that can change the flavour profile and it’s hard for people like us, that buy few kilos of green to know all of them. I suppose big roasters know a bit more of how farmers process the coffee and even the weather conditions of a particular year. Than even green coffee changes over time(that is influenced by how it is stored too). So you might have bought a fresh harvest and then an older one. Than you have the roasting and resting that both can influence the flavour. I’ve been drinking a lot of un-rested coffee, as I roast when running out of coffee. And light/medium roasts need longer times to rest. In my opinion at least a week, if not two.

I’m only buying 5kg at a time as it’s easier to work with only one type and improve on that. But I see what you mean. Ideally you would live close to someone that is also roasting and can exchange green coffee. Alternatively, you can always give away roasted coffee for free as presents. Not very cost effective though.

cafesolo

I thought I’d register and jump on this thread, since I’ve been having a lot of trouble getting even roasts on my gene cafe. I’ve had it for maybe two years now, and have had a lot of good roasts, but lately every roast seems quite uneven.
This is probably partly due to my poor bean purchase/planning, as all I have at the moment are Ethiopians, which have always given me more trouble.

I have a 230v machine (living in Spain) with a dimmer mod. Normally my roasting process has been like (pretty much always 250g):

preheat to 200C
1250W until the exhaust temp hits 210C
1200W until 220C
1150W until 15-30 seconds past first crack
drop down to 600-700W until done (usually around 1:30 after FC)

That’s often been quite nice. Usually FC happens at 230C exhaust temperature, in around 9-11 minutes.
But, I have trouble with unevenness, and lately even more uneven.
I’ve tried all kinds of things: disassembling/cleaning the chaff collector and fan and lowering wattage. I just tried following some of the advice in this thread: no preheat, starting at 1150W, lowering to 1130W during yellowing, FC at 14minutes/230C. I can’t really say that the result is much better (some scorching and general unevenness).

Any advice? Should I just try lowering the power even more to start (or later in the roast to keep the exhaust temperature down)? Change the batch size? Preheat?

@Dan have you had any improvements?

As an aside, I’ve also always found it really difficult to follow advice/recipes for this machine, since the temperatures never really make much sense to me. Roast rebels, for example, has a page of suggested roast profiles and those temperatures, my machine would just be on full-blast the entire roast. I gather that temperature reading can just vary a lot from machine to machine (I even replaced the probe at one point).

oddbean

cafesolo I thought I’d register and jump on this thread,

welcome to the forum!

I thought this is an issue for all coffees roasted on the Gene. What worked for me was to lower the batch size to 230g.

I also have a 230V heater even if I live in UK (as it is a 2008 model) with the dimmer mod. I usually buy 5kg of same green coffee and just play around with different profile, see what I get.

Have read somewhere that you should lower the heat for development just before FC. And I have never lowered the power that low before. Usually i lower it to 950-1000W just before or when I hear FC.

Doram

cafesolo but lately every roast seems quite uneven.

Not sure what you mean by “uneven” (maybe upload a photo?), but I find that some beans result in very different look than others even when roasted very similarly. So if you have noticed a change in evenness but it’s not the same bean - then it might be meaningless and nothing to worry about.

cafesolo 1250W until the exhaust temp hits 210C
1200W until 220C
1150W until 15-30 seconds past first crack
drop down to 600-700W until done (usually around 1:30 after FC)

The other thing I noticed in your message is that the only significant decrease of power in your process is at the last stage (15-30 seconds after FC). If you take into consideration that the heat loss isn’t instant and that the beans will coast after you reduce the power, you might want to try and do a more significant reduction of power, and do it earlier.

Personally I find that I’m getting better results if I reduce the power of the heater more aggressively as soon as the first crack starts. I don’t have a power meter, so can’t give you numbers in W, but if full power is 12 o’clock and turning the dimmer down is anti-clockwise, I maybe go to 11 just before FC, but as soon as it starts I go to around 7. The residual heat in the chamber and beans + the heat that is still pumped in from the heater is enough for me to keep the crack rolling, but I have more control and slow things down a little so the beans don’t burn. Think of popcorn - if you take the heat down significantly the corn will continue to pop and you get nice results, but if you keep the heat on high - you will burn the popcorn.

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