How Does Batch Size Affect Coffee Roasting Profiles?

[@LivingTheLifeRetired]

Great video. On my M1 I’ve only been using a batch size of 150g, which is 75% of the capacity. I do that for efficiency reasons, as there are 454g in a pound, so I can roast 3 times without leftovers! I don’t feel the need to add yet another variable to mix so keeping the weight constant is helpful for me. Thanks for the video.

[@VirtualCoffeeLab]

Thanks for sharing Edward. Great advice!

[@robertroth287]

Since I am new to this hobby, I think I will keep my charge weight the same to avoid one variable in the roasting process. Your video was very interesting, as are the comments and responses.

[@VirtualCoffeeLab]

Hi Robert. The fewer the variables the better. That way, you can see how a single change affects your event times. Thanks for watching! I’m glad you are enjoying the comments, they can be really helpful.

[@18banderson]

As always, great video! This is one of my favorite roasting channels.

[@VirtualCoffeeLab]

Thanks for watching and being a subscriber Ben!

[@luigicollins3954]

Oh Mike, I was riveted to watching this video! It is exactly the video I’ve been waiting for. For any particular coffee, I work hard to achieve a roasting plan that yields a delicious cup. Then (for various reasons) I sometimes must use a different batch size, but still want that same wonderful roast profile. I use a drum roaster and can verify 100% the findings you have reported here. Simply put and pretty obvious, when batch size changes I have to modify the amount and timing of both heat and fan in an effort to get the same roast profile. And pre-heat temperature and initial power level are also EXTREMELY important! After the roast starts, the best (easiest and most accurate) way I have found to control profile is by strict control of rate of rise (ROR) for all three phases. Using temperature values from previous golden cup roasts, I can calculate a required ROR for each phase. If the RORs are the same, the roast comes out just right. The difficult part for me is learning how much of a difference there might be from various batch mass changes. From things I’ve seen, a change of 10 or 20 grams doesn’t seem to have much effect whereas a change of 50 grams definitely does. Lately I’ve been pondering increasing my standard batch size from 350 g to maybe 390 g, to get my final yield close to 340 g (12 oz). Anyway, this subject is really important to me at this time. Thanks Mike.

[@VirtualCoffeeLab]

Thanks for the confirmation and for sharing Lou. I have found that increasing my charge temperature for the larger load works well to get me closer to my dry time. It usually ins an increase of about 10 degrees when I go from a 300 gram roast to a 400 gram roast. I then compensate my heat along the way to achieve the ROR I desire as you do. Thanks for sharing Lou. I appreciate the support. I'm glad you liked the video.

[@robertcombs8730]

I have been roasting with the sr540 for about 3 and a half years now and about one and a half of those years with the Razzo extension chamber which is similar to your extension. I am not using software but I use the machine temperature along with the bean probe temperature and an exhaust temperature in the chaff collector vent slot. I also have to make tons of adjustments due to ambient temperature because I roast in an attached garage which is not heated. I have my sr540 in a vintage metal cooler modified to store heat and as the roast progresses has flaps to control temperature inside the cooler. Your test makes total sense to me. If you were to continue to decrease batch size you would hit a point where the bean mass would not hold and store enough energy and the roast would not complete. On the other hand if you increased the batch size the mass would hold the heat to the point of not being able to heat the total bean mass due to not having sufficient bean movement to ventilate and agitate resulting in an uneven roast. I will use your results as a reminder of what is happening so I will be ready to make as needed adjustments. Thanks again for your time, dedication, and knowledge. This is very helpful to all of us regardless of skill level.

[@VirtualCoffeeLab]

I'm glad this video was helpful Robert. Agreed, there seems to be an optimal batch size to achieve a specific profile curve. Finding this weight is the nugget. BUT, this would be bean-specific. I have not tested what would happen using a different bean but I suspect it would be similar to what happens when we roast a different coffee. Some are higher density, smaller, etc.. The metal cooler with the flaps is pretty sweet. Thanks for watching & sharing.

[@andreamunari5800]

TY

[@VirtualCoffeeLab]

Thanks for watching!

[@thecoffeescientist3746]

Thanks for the awesome video! Definitely going to use the information

[@VirtualCoffeeLab]

Thanks for watching. Let me know if your results are similar

[@thecoffeescientist3746]

​@@VirtualCoffeeLab Even changing the batch by 140 g to 138 had a different result the 140 g was darker than the 138 g was lighter roast

[@VirtualCoffeeLab]

Yes, even minor changes in batch size can impact the profile.

[@madjaffa]

I’ve been pumping through all your content. I’ve been roasting for ages now but only recently been drinking more black so have noticed that most of my roasts seem to be lacking any fruit notes. I think it’s coming down to I need to drop my roast size / trying to push my machine too hard. Typical charge is 550-600g and I don’t get anywhere near a 20-25 starting ROR. Lucky to hold above 13. I think this is extending my dry phase to long (~6min) which in turn extends my overall time to 12+ min. Only recently I discovered the 20% “rule” for the dev phase and I think I need to play with lower going by some of your videos. Next roast day will be trying to hit a 10min with 300-400g + lower charge temps (my usual was 230-250) and aim for a 50/35/15 to start with. Try and hit that fruit 🤞 . FYI: Roaster is a DIY hand me down. Bowl with agitator and turbo oven halogen lid. I use a voltage controller to turn down the heat, (which unfortunately turns down the fan at the same time)

[@VirtualCoffeeLab]

Hi Geoff, thanks for watching and your comment. The 20% rule and the overall 50/30/20 is a starting point. It isn’t the only way to roast. It is meant to get people to a place where they are beginning to control their roaster and produce decent coffee. A lower batch size should make a difference. I wouldn’t lower the charge too much if any and see how quickly you can get the coffee to turn yellow with your DIY. You didn’t mention the type of coffee you are roasting but I’ll assume it is a higher altitude coffee. I like your percentage breakdown with the 15%. One way to monitor roast level is by measuring moisture loss. If you aren’t doing that you should start and compare roasts. It is very enlightening. Oh, by the way, are you preheating?

[@madjaffa]

@@VirtualCoffeeLab Ok will give that a nudge. I’ve got a ton of some cheap Peru (prob quite old), which is my main milky drink bean and tester bean. But the ones I’ve been trying to get fruits in are various Ethiopian beans, most recent:“Ethiopia Ardi is a natural processed coffee from the south western highlands and was sun dried on raised beds. This coffee is a fruit-bomb, lush red berries and fat floral aromatics off the grinder”. When I run it over a chemex pourover I get a quite a smooth coffee, roast notes but only a touch of acidity and no fruit. I also was using an automatic 150c as dry end and prob need to check it on test batches. Unfortunately I don’t think I can check it without causing heat loss or crashing as the lid would have to come off and quickly scoop up some and chuck it back in 🤣. Yes the moisture was the other thing I will be adding to the process. Wasn’t really bothering with moisture loss and going by colour and taste of chomping on the bean to get a rough idea of the roast level. Potentially my preheat might be too short 10-20min at the 250. A lot of the time I run a batch of Peru first, so by the time I want to run the better / fresh beans it should be warmed up.

[@gvalley1]

I had the exact same results when I increased the amount of beans. The roast finished 5 minutes faster! I should have watched this first. It was very surprising. I'm glad it was a Sumatra

[@VirtualCoffeeLab]

One of the things I didn't talk about in the video was what happened towards the end of the roast on the larger batch size. Notice how the ROR increased (flicked upward) at the end. So, in this case, to keep the temperatures down a little you may need to reduce the heat one step. If you are not using artisan, then maybe watch the increase in temps on your Fresh Roast temp readings to see if you notice this. Then, adjust as necessary. Does that make sense?

[@gvalley1]

@@VirtualCoffeeLab yes it does make sense. I'll let you know . I still have some more Sumatra to roast and I don't want to roast all the flavor out of it. We love your videos. You are very good at explaining the process and watching them makes us feel like experts. But we still come back and watch again. Lol.

[@GVLBuckeye]

Mike, thanks for addressing this topic. Can you do a video about the differences in roasting Peaberry beans and the differences between them and a normal bean? I have some Tanzanian Peaberry and when I roast using my typical profile the brew seems bland. I'm using a SR800 with the expansion tube. Thanks,

[@VirtualCoffeeLab]

Brian, thanks for the comment. Can you tell me how your event times and temperatures might have been different between the smaller peaberry and a normal bean? I have some comments to make but I wanted to hear more about the two roasts firsts. - thanks.

[@GVLBuckeye]

@@VirtualCoffeeLab Yesterday after watching one of your videos I tried a lighter roast. I'm trying it for the first time now :) TBH, we don't prefer it. It seems very acidic and not much body. Maybe we just prefer a darker, full city type of roast. Here is a generalization of the profile I used. I started 7-4, temp rose to 396 degrees at 3:00 mark. I increased the power to 6. Temp steadily increased 420 at 4:00, 426 at 5:00, lowered the fan to 6, temp at 5:30 447 degrees, 6:00 at 454, 6:30 at 470 degrees. 1st crack around 7:00 at 480 degrees. changed the temp down to 3 so development would be prolonged (6-3 setting now) Temp started going down, 7:30 at 455, 8:00 at 441, 9:00 at 435, ended the roast at 9:30 with a temp of 432 degrees. I really appreciate your advice.

[@VirtualCoffeeLab]

Brian, thanks for trying it out. Please refresh my memory. Which fresh roast are you using? I'm curious, are the temps you are referencing the fresh roast temps? Which coffee are you roasting?

[@GVLBuckeye]

@@VirtualCoffeeLab FR800 with extension tube, yes these are the temp readings from the Fresh Roast panel. Tanzanian Peaberry.

[@VirtualCoffeeLab]

Brian, Thanks for sharing your details. You didn't mention when you hit dry end (yellow) but based on what you have shared so far the bland flavors a because of the longer development time. At least this could be one cause of the less complex and flat notes. Peaberry beans are small and dense. I think you could increase the overall speed of the roast. Nine minutes and thirty seconds is pretty long for that bean in the fresh roast. Shoot for a 3.5 minute dry event. Target a first crack time of about the 5 minute and 45 second time on your roast. Once you hit first crack, let the beans roast for another 1.5 minutes ending your roast about about 7:15. The SR800 terms are probably different than my 540 because of the batch size. You will need to adjust your heat to hit your dry event and still maintain good bean movement. I think that making fewer heat adjustments might be helpful. In this video I only made one heat adjustment. Everything else was done with the fan. By Dry End I only made one adjustment and let it ride as you can see in this video. I hope my comments are helpful and make sense. I'm confident the bland tase is from a longer development, possibly even a middle phase that is a little too long. If you are saying that the coffee was a little on the light side and it had a 2.5 minute development then that also tells me your ROR during that time was flat and your ror crashed. You said your FR temps went down. This is also a cause of your bland flavor. Some might call what happened (baked). Your ROR should always be in a positive rate, just declining. So in my video you see my ROR go from about 30 at dry end down to about 7 at drop. This is not the temperature of the heat but the rate of increase temperature. The darker blue line is my temp which is always going higher. .... just at a slower rate. Let me know your thoughts about what I shared. I will be glad to clarify.

[@Ufsnp1963]

Спасибо Большое! Очень полезно!!!!!! Надо обязательно попробовать! Продолжайте! Вам удачи!!!

[@VirtualCoffeeLab]

i am glad my video was helpful. Thank you for watcing.

[@GoTellJesusSaves]

After watching this video I went back and watched the Nordic Roast video on the SR as well. Was inspired to try a couple roasts of my own. I don't have a heat probe or the chaff collector screen on my machine, but do have the same extension tube on the same machine. I used your video to understand the ROR a bit better, then adapted my roasting more closely to your Nordic style roast, with some obvious distinctions. I simply began at 8 fan and 1 power setting, then made changes every 30 seconds until I reached 5 fan and 5 heat settings as shown below. Turned out fabulous with the coffee I'm using. I hit 1st Crack at 7:55. Had 1:25 development time. Not sure about the dry phase, as I am a bit color blind and can't tell when green to yellow happens. If I had a thermocouple, I could just use a certain bean temp instead. 150g charge weight Huehue washed greens Time in the left column is total roast time at event. Right column time is time between events. 8-1 start settings 01 00:30.72 00:30.72 8-2 02 01:00.44 00:29.72 8-3 03 01:30.58 00:30.14 8-4 04 02:00.56 00:29.98 8-5 05 02:30.86 00:30.30 7-5 06 03:00.52 00:29.66 6-5 07 03:33.27 00:32.75 5-5 08 07:55.45 04:22.18 1st Crack 09 09:21.16 01:25.71 Drop Light roast. Good development. Excellent flavor! Very enjoyable cup. Delicate. Sweet. Balanced acidity and sweetness. I have found that starting off with a lower temp setting extends the drying phase slightly and increases the sweetness/decreases harshness. In essence, it makes it a smoother drink on the tongue. Could drink this all day without fatigue to my tastebuds. Thanks a bunch for the great tips and probe info! Drastically changed my experience with this roasting machine!

[@VirtualCoffeeLab]

Thanks for sharing Jason. Are you tracking temps using the built in temp/thermister? I'm curious what your temp was on the fresh roast at the time of drop.

[@GoTellJesusSaves]

@@VirtualCoffeeLab glad to share! The machine was showing around 416-418 for the last 2 minutes of the roast. It may have gotten up to 420 at the highest point for a moment.

[@GoTellJesusSaves]

@@VirtualCoffeeLab I did have the windows open, letting cold Missouri air into the room where I was roasting. So ambient temp was around 60f.

[@GoTellJesusSaves]

@@VirtualCoffeeLab Oh! Also I found that putting the fan speed up to 9 when cooling makes a huge difference in how quickly the coffee cools down. That and having the cold air coming in the window towards the machine surely has a good effect on it for cooling purposes as well.

[@VirtualCoffeeLab]

Thanks for the reply. Yep, that is about the range I was in as well. The ROR was declining at a fairly minimal rate during development.

[@ajk2749]

As at least one person mentioned here, I roast an amount to get equal charge weights from a 5 pound bag for my Hottop B-2K+ using Artisan (252 grams). That also results in a roasted weight that gives me a nice even 7 days of brews! I might drop it down to 206 grams the next time I have a 5 pound bag to start with.

[@VirtualCoffeeLab]

Adrian, how are you? Glad to hear you are still roasting on your Hottop. Yea, I've heard others say something similar. They set their batch size based on usage. That is a great idea as long as you can still roast the profile you want. Do you find you need to change the charge weight for different profiles using the Hottop? Some roasters don't have the horsepower if they have too large a batch size.

[@ajk2749]

@@VirtualCoffeeLab Thanks, Mike. Yes, I'm still roasting and really enjoy the end results of my efforts but I do have trouble controlling the 3rd phase especially. Usually it winds up too hot so I have to anticipate 1C a little better. Lately I'm roasting either 227 grams or 252, depending on whether it's from a 2lb or 5lb bag. I have not roasted the same bean with different charge weights so it's hard to say how much of a difference that makes for me but perhaps dropping down to 206 grams will give me better control. I won't be ready to order coffee for a few months so I'll continue with my present profiles. Right now I'm trying to get the Hottop to do an automatic roast profile using Alarms but the first attempt was unsuccessful. I'll try again in a few days. A friend of mine who was a long time Hottop user (since 2006) just got a Kaleido M2 based on your videos and he's enjoying the results as well with its larger capacity. Thank you for the videos. I'll be watching.

[@Poundy]

I roast to request, so for me there's no "perfect" batch size. Some times my batches will be 2100g, some times 2000g, some times 1800g.... usually I limit my end points to the 1800-2200g range. From that, I will still use my same desired profile and aim to track milestones to meet that - and usually aiming to have as little variance as possible. But at the end of the day, I'm using my knowledge of my roaster and my coffees to try to stay ahead of how the roast is going, to do that. For a beginner, your demo here is a great one that shows how you can make one change and see different outcomes. But I feel that the kinds of scenarios you point out are not that "common", in that it's unlikely you'd want to try just a little darker roast and artificially keep to the same drop point - you're more likely to stretch the dev time with a similar trajectory through Maillard. Having said that, it's critical for new roasters, or those with new machines, to understand how adjusting controls changes outcomes. In a drum roaster, a good example is as you say tweaking airflow - until you understand the points on your airflow control where you go from causing greater convection in the bean mass to causing it to pull heat out of the bean mass, you don't really understand how to manage temperature projections with that airflow... so these experiments are really really important to understand.

[@VirtualCoffeeLab]

Great comments Brett. I tend to roast a variety of charge weights for similar reasons and knowledge of the roaster and experience how that coffee behaves when we apply heat will help us hit our roasting event milestones. I’ve just recently been roasting on a 1.2 kilo (double the capacity of my Mill City 500 gram and boy things are a lot different. The coffee mass really plays a roll in temps. It is quite the learning experience. Thanks for watching and your comments. I always appreciate the experience you share!

[@dionb112]

@@VirtualCoffeeLab Do you think there is a 'minimum requirement' for weight put into the M10. I found a really good price on one but am a little afraid that doing smaller batches inside it will not be suitable for quality roasting.

[@VirtualCoffeeLab]

@@dionb112 I roast as little as 300g but mostly 400g-800 grams per batch on the M10 with no trouble. On the lighter loads I need to keep the trier turned upside down a little longer to catch some beans but it hasn't been an issue for me.

[@BigBlockESPRESSO]

Thanks in advance Mike. I need some roasting advice. I often find myself with pounds of wasted good beans. Most of my roasts (65-70%) turn out tasting “green / soil / earthy”. Im 6 months into roasting and I roast for espresso use. My roasting setup is Stove-top perforated electric drum & infrared thermometer + hand fan. I use a roast timer & weight calculator. I also log the events + time that happen during a roast. Mostly, I roast Natural and Anaerobic Natural Ethiopian coffee. Generally, my aim is Medium-Light Medium. My roasts are typically 8-10 minutes. (15-25% development). I have watched most of your videos and “How to roast sweeter coffee” tutorial. And still am not getting the results I want. I’d be thankful for some tips & advice

[@VirtualCoffeeLab]

Uneven roasts occur more often with naturals. You might notice the color variation after roasting. So, the bean you are buying might have something to do with this. Ok, now for the roasting. Please share the event times. How long to dry? How long to first crack?

[@BigBlockESPRESSO]

Normally I hit Dry End at 4:00-4:30, then another 2-3 minutes in Middle phase. After, from FC I usually develop up to 20% if my Middle phase was too short (to compensate). And 11-13% when Middle phase is longer.

[@VirtualCoffeeLab]

Hmmm, after thinking about this more and hearing your response, I have two thoughts. First, you want to have a middle phase that will last at least 3 minutes, maybe a little longer. That means you will need to reduce the temp a little more during this phase to stretch it out. This will help part of your development problem, especially since you are shortening your development time to maximize for acidity. Second, you said you have a perforated drum. Is this insulated inside a box? What are you doing for airflow? I'm a little concerned you are apply heat to the surface of the drum to maintain increasing temperatures while you are loosing heat because of a lack of insulation. You need to have convection heat transfer, not just conduction to attain a more even roast. This conduction heat will help the heat penetrate more efficiently into the bean. Not knowing exactly what type of roaster you have, consider consider this as a potential issue. It can make a difference between an even or uneven roast. Ultimately, It sounds like you are not roasting the bean all the way through and this is due to the amount of time spend in that middle phase. One of the challenging skills for me is to keep that middle phase in control. It is a good idea to practice aiming for a specific dry end event time and a specific first crack time. Doing this forces you to stay in control of your roasting phase times. Let me know your thoughts on this.

[@robertcombs8730]

180g is my regular batch size. It seems to be the easiest to adapt to with different beans. My voltage fluctuates day to day and even hour to hour so it is hard to keep a specific profile due to this. I think this is a very important factor and also should be taken into consideration when trying to trade profiles. I took my roaster to my cousins house on Wolverine Lake and she did not have enough voltage for me to complete or control a roast. The power grid was too weak. Before I roast I check my kilowatt meter and ambient temperature and then I have an idea of what to expect. A big positive for these small roasters is the ability to make adjustments on the fly and correct potential problems as they arise. I am always trying to figure out a better way to achieve consistent and better results but for now I am drinking excellent coffee with very few bad roasts.

[@VirtualCoffeeLab]

That's great info Robert. Thank you for sharing. If you look at my video "fresh roast light Nordic style roasting profile using artisan" notice I display the voltage meter in the top center of the screen. Does your watt usage look similar to mine? kzbin.info/www/bejne/gGSqdn5vrsl9qJY Thanks again for being a subscriber!

[@nickr9784]

For your two thermocouples are you doing bean temp and exhaust temp?

[@VirtualCoffeeLab]

Hi Nick, yes, I am using two probes for bean temp and the inlet temp which we can call exhaust temp. The positioning of these is really important. I positioned my holes in the chaff collector lid so the shorter BT probe is near the center of the lid. The ET (long probe) is placed somewhere around the 10 o'clock position if you are facing the roaster and the hole should be positioned so when it goes down into the tube, it reaches the metal bottom of the roasting chamber and goes in one of the small holes. With my setup, I get the visuals of a typical artisan graph with my ET being the red line on top and the dark blue line being the BT. I can manage my momentum by monitoring the ET max rate to help me stay in control and not get too hot. The positioning and length of the BT I chose is based on the concept IKAWA uses with their roaster. The BT is at the top of the chamber and does not touch the bean mass. I think this is helpful because with the air roaster, getting a true Bean Temp further down into the bean mass will be skewed because the probe is so close to the inlet temperature (the heat source). I've tried and the result is two lines on a graph that are very similar. This is not helpful for me so that is why I prefer the higher probe. I get use to the temp readings of the BT with the probe there and then I can better anticipate roasting events.

[@joemacias2360]

How does the shorter hotter drying phase affect the taste?

[@VirtualCoffeeLab]

Hi Joe. The drying phase doesn’t have much impact on taste. The amount of time spent from the beginning of the Maillard reactions through the end of the roast are what matter most. The shorter hotter roast will have an impact on the flavor. In my case with this video using the fresh roast, the hotter, shorter roast gave me darker notes and more harshness.

[@skyt54]

How do you hook up two roasters to Artisan? Also you have way more buttons on your graph that on my artisan graph, does that change depending on what roaster you select in artisan. I presently have a Quest M3 drum roaster and only have two thermocouples, there is no way to monitor fan speed. I just orders a MC500 Mill City roaster so i am guessing when i select that roaster i artisan some more buttons and or sliders will be present in artisan.

[@VirtualCoffeeLab]

I hooked up the two roasters differently. I use my "portable probes" for the Behmor and Fresh Roast. They use my old Phidget 1048 with some probes for that setup. The Kaleido has its own probes and temperature sensing stuff. As far as the the buttons, you can add buttons or sliders to your setup inside artisan. You can choose heat, air, drum. So, for your quest, you don't have to be connected to monitor fan or drum speed, just mark it manually in Artisan when you make changes.

[@jamesshepherd7727]

I have a question about the suggestion on the bag for roast profile. My current bag says city to full city. Some of my bags say city plus. As I look around through various places these names mean different things. Some say city is light roast and full city is medium light and city plus is full medium. Others say city plus is on the verge of a dark roast. Why is there no standard for roast levels. Should be a standard for what each part of a roast is. Like what is the level at end of first crack. Beginning of second. So forth. At this point all I do is time to a certain point in my roast and try it. But I have no clue as to what the roast should be called. You would think at this point in time there would be a standard.

[@VirtualCoffeeLab]

Hi James, Sorry for the slow reply. Yes, I have seen this as well. I think the SCA (Specialty Coffee Association) uses Agtron scale to determine roast level. Home roasters don't have this equipment because it is expensive. This might be why we talk in terms like Light, Medium, Dark, City, City+, Full City, etc.. I don't know for sure. This link is helpful but again, it is Agtron BUT they also use terms like light, medium, dark along with the Agtron number. www.coffeereview.com/roast-definitions/ With regards to why the sellers use different terms, I have no clue. It is frustrating.

[@JuliusSP1]

Hi Mike. On the 6 kilo roaster I roast on by mill city, we consistently get peak RoRs of around 32 to 35 deg. F per min. On this M2 which I'm considering purchasing it shows about 73 degrees per min in your videos? is this per 2 mins or is it just that much faster at the start of a roast or throughout the roast on a smaller drum roaster? I guess this has to do with the batch size and how it affects thermal energy transference as you're covering in this video? Also, for the M2, is 300 grams the best size for creating the absolute best roast of any coffee, or is it just simply the easiest way to find a sweet spot for a roast on thr machine? Cann you go from 300 grams to 200 grams and achieve eventually the same results in cup quality or is that unlikely? Thanks for your help. This video was great and very educational.

[@VirtualCoffeeLab]

Julius, please tell me the exact time in this video where you see the 73 peak ror. My m2 usually peaks around 25-27 unless I give it 100% and use a lower charge weight, then I can get in the 30’s As far as optimal batch size goes, the M2 is great for 200-400g. Are you trying to match the exact profile I used with the 6k? Are you thinking of using the m2 as the sample roaster? Just curious what you’re trying to work out. The M2 is a great small sample roaster but isn’t going to roast a little different than the 6 kilo roaster. Your temps will be different between these two roasters and the M2 will be quicker to respond to input changes. The 6 k will hold heat a little better. As far as batch size goes, what type of roaster is your 6k? I’m curious what the min-max capacity is?

[@JuliusSP1]

The roaster we use is the Mill City 6 kg. You know, I am mistaken on the RoR. I was assuming the temps were in Celsius in this video and in another roast video with the M2. So when I saw 25 as delta BT I converted it to F which was over 70 F. I would like to be able to take profiles from the larger MCR6 and apply it effectively to the M2, and vice versq, take some recipes for the M2 that you provide and transfer them to the Mill City. Just so I can get used to making adjustments between machines of vastly different sizes and power outputs and heat retentions. That's good to know I can roast as low as 200 grams for a batch and have the quality come out pretty close to a 300-gram roast.

[@JuliusSP1]

Just to clarify, I think it is the video where you're roasting a natural Ethiopian on the M2 where I'm a bit confused about the RoR. You're reporting the RoR peak at around 20 or so in Celsius. Whch would be quite high?Maybe I'm confused or misunderstanding something however.

[@VirtualCoffeeLab]

Transfering profiles isn't always straightforward. The type and size of the machine will make a difference. I believe there are two big factors we need to match up if we are trying to "transfer" a profile. First, I have found that aiming for event times is a great starting point. If the source profile has a first crack time of 8 minutes then I want to match that with the target roaster. That might mean different power and air settings for the target roaster. So, Dry, First Crack, and Drop events should be matched. Second, the end color needs to be the same between the source and target roasters. If you care to give that a try, let me know how it went. I realize roasting 5-6 kilos of coffee is different than 200-400 grams. You are dealing with a lot of coffee to heat up and then there is the inertia of the roast for that bigger roaster. That is why your heat and air settings will be different. What do you think?

[@deenman60]

Great video and tips. I like your video format. the difference on the freshroast between 140 and 180g can be the beans lofting less on 180g so the heat remains trapped more in the chamber, instead of escaping between the more space generating by 140g/same air setting. This would translate in more heat into the beans with a bigger load since lower agitation=darker roast and more weight loss. On the drum roaster this effect is not existent since you agitate manually and the energy is stored in the drum mass and a bit in the hot air that has to escape via the exhaust system.

[@VirtualCoffeeLab]

Thank you for watching and for sharing your comments. Yea, on the drum roaster uses conduction heat early in the roast. More beans in the drum translate to less conduction. Then, when we get further into the dry phase, the beans pass heat to each other when they touch. This is still conduction heat. Convection heat with the air is taking place throughout the roast using the same airflow setting on the smaller roast. This may be impacted by the larger batch but it isn't enough to have a huge impact. Most of this slowness is because there was less contact with the hot metal early on in the roast.. At least that is my understanding of what is happening with the drum roast. There is so much air being used in an "air roaster" that it is pretty much 100% convection roasting. Not much bean to bean contact once the beans start to loft.

[@sunnycharacter]

So, if I’m understanding this right, the bigger the batch for a darker resulting roast, because the more beans holding heat increases heat and makes a darker roast? Does this depend on the type of bean, and using the extension, is a 8 to 9 ounce raw batch fine for a balanced roast? I tend to roast high grown beans, med to dark roast, but not espresso dark. My batches turn out great on my FR 800 with extension.

[@VirtualCoffeeLab]

Hi Lori, with an air roaster where heat is blasting from underneath into a cylinder, like the fresh roast, YES. There is a range where this will work. The heavier the batch the more smothering the green beans will be over the heat, leading to an uneven roast. I you have been using a profile that works and you are happy, don't change anything. If you want your roast to be a little darker, add a small amount of beans and see how that changes your roast. You would treat different coffees like you are already doing. Find the profile that works for you and then if you want to go a little darker, all a little coffee. You should experience the same effect.

[@sunnycharacter]

@@VirtualCoffeeLab makes perfect sense thanks! I am generally happy with my roasts. The only difference I’ve noticed is with a bag of beans, still sealed, but an older purchase have exhibited a slightly drier moisture level than when a bag freshly shipped was roasted. So I anticipate that an older bag will have lost some moisture and adjust my drying phase accordingly.

[@richardhenderson9127]

The smaller batches take a little bit longer to heat up. It seems like they take a little bit longer to hit first crack.

[@VirtualCoffeeLab]

Which roast are you referring to Richard?

[@richardhenderson9127]

@@VirtualCoffeeLab the FreshRoast roasters. The heat came up hotter on the 182 gram. It did the same thing when I used an Ethiopian roast profile that you did a while back with 250 grams using my extension tube. Had to tame it down a little towards the end.

[@VirtualCoffeeLab]

OK, thats interesting and it makes sense. So in your example, maybe a slightly lighter load may have prevented the heat adjustment you needed to make near the end of the roast? Thanks for sharing Richard.

[@jlantz3691]

The fact that your lighter batch reached both dry end and FC sooner and cooler than the heavier batch seems counterintuitive to me. While I haven't done a side-by-side comparison like you, heavier batches get hotter quicker, and in response, I have to toggle down power/fan to compensate if I want to keep both batches at the same roast level. I would imagine that's because the larger bean mass holds more heat. That said, it seems that the heavier batch would reach dry end and FC sooner at the same fan/power settings because of the hotter temps. Where am I going wrong in my thinking?

[@jlantz3691]

I'm referring to the FR in my comment.

[@GoTellJesusSaves]

I would think it has to do with the reading and placement of the thermocouple. It will read the larger mass hotter the lower it is in the bean mass. Because that air isn't flowing through the mass as easily. Basically more hot air is getting trapped down low in the chamber. Also it's possible that the smaller mass probably also is able to lose its moisture quicker as the airflow through them is agitating them more readily and the moisture escapes the chamber quicker. That may be a stretch? These are just speculations, of course.

[@VirtualCoffeeLab]

The heavier roast has more beans to heat up from the room temp. This is why you see collier temps during the dry phase when using a heavier load with the air roaster. While the light roast did reach fc sooner on the time line. This was because the larger roast took much longer during the dry phase. In my video I mention that both roasts had the same browning phase time. It was the first crack event where we really see the higher temps. There is a 9 degree higher fc temp with the larger roast. I see this as “momentum”. When we have more heat on the front end of our roast. We have momentum, like a large/long train of locomotive that takes longer to speed up but once it gets going there is no stopping. So we have higher temps that cause this even though the power and fan settings unchanged. This is what I was talking about. The profile did change. The temps are different and the development time is different. The bean mass on the larger volume traps the heat, creating a biter roast environment once the beans dry

[@jlantz3691]

​@@GoTellJesusSavesActually those both seem very reasonable explanations. Thanks for the input.

[@jlantz3691]

​@@VirtualCoffeeLabThanks Mike. Always learning from you!