Increase drum speed to 60hz and try again.

I had the same results as before. What am I doing wrong?

I tried to upload a picture but couldn't get it to go.

Have you considered adjusting your heat application? I will reference Robert Hoos' book on modulating coffee flavor profiles. In there he cites a study that has demonstrated that formation of melanoidins are inhibited as pressure increases. If you're roasting too hot and fast for the coffee you're using, the beans may not have enough time in the Maillard phase to brown efficiently and evenly.

@WeirdBros said:

Have you considered adjusting your heat application? I will reference Robert Hoos' book on modulating coffee flavor profiles. In there he cites a study that has demonstrated that formation of melanoidins are inhibited as pressure increases. If you're roasting too hot and fast for the coffee you're using, the beans may not have enough time in the Maillard phase to brown efficiently and evenly.

Wondering if you might be on the right track. I have tried full batches about 10 times. It says on the website that it will do a batch size of 3.6 Kg. When I say full batch I am referring to anything over 3Kg up to 3.3 Kg of green. Since I have lost so much coffee I am scared to try it again. So focusing in on where things start to go wrong I am wondering if it isn't too much heat when it gets to the top of the ROR and starts the down path. What is hard to understand is how only 200 - 500 grams of green make so much of a difference. Same settings as I do on a batch of 2.8 Kg and am super pleased with. On full batches so far the first crack comes early, which is why I am wondering about too much heat, and then it is like I can't control it any more. I move the fan up as high as I can without sucking all the beans out and drop the temperature down but by this time it is too late. Now it is just mitigation to leave a coffee that is at least donate-able. I finally was able to get a picture to upload. Does anyone have a Roast Path link of successful 3.6 Kg roast on the same machine? A Brazil semi washed?

Of all of our roasters, because of the drum volume to BTU ratio, the 3kg is the most sensitive to batch size.

Larger seeds like that Brazil expand more and sometimes enough to inhibit mixing in the drum at full batch size.

The first step is to increase drum speed. Second, if possible relative to the target flavor profile, roast longer and slower. Third, if necessary, is to decrease the batch size.

@youandme said:

Wondering if you might be on the right track. I have tried full batches about 10 times. It says on the website that it will do a batch size of 3.6 Kg. When I say full batch I am referring to anything over 3Kg up to 3.3 Kg of green. Since I have lost so much coffee I am scared to try it again. So focusing in on where things start to go wrong I am wondering if it isn't too much heat when it gets to the top of the ROR and starts the down path. What is hard to understand is how only 200 - 500 grams of green make so much of a difference. Same settings as I do on a batch of 2.8 Kg and am super pleased with. On full batches so far the first crack comes early, which is why I am wondering about too much heat, and then it is like I can't control it any more. I move the fan up as high as I can without sucking all the beans out and drop the temperature down but by this time it is too late. Now it is just mitigation to leave a coffee that is at least donate-able. I finally was able to get a picture to upload. Does anyone have a Roast Path link of successful 3.6 Kg roast on the same machine? A Brazil semi washed?

It's crazy to see how much a seemingly small amount of additional beans can affect so much but that it still extra moisture that the roaster has to dry off. From your drop temp, are you looking for a city+/full city roast? In my experience I try to aim for no less than 3:00 in MAI phase in that case. I would suggest making a couple incremental decreases of gas pressure and incremental increases of fan speed at set points throughout the roast. This will help keep you ahead of the ROR curve and allow you some wiggle room to make slight adjustments as the roast progresses. Hopefully it will also help even out the roast color. If still too fast, then next step would be to initial gas pressure.

Not that this is a 1:1 transferrable profile but this will show what I mean with the incremental changes.

https://portal.roastpath.com/publicroasts/index/32652230917250523

To be honest, coffee roasting is half science and half magic. Some days the stars just aren't in alignment and the roast machines and beans decide to rebel. Don't be discouraged, we've all been in that same boat!

@WeirdBros said:

It's crazy to see how much a seemingly small amount of additional beans can affect so much but that it still extra moisture that the roaster has to dry off. From your drop temp, are you looking for a city+/full city roast? In my experience I try to aim for no less than 3:00 in MAI phase in that case. I would suggest making a couple incremental decreases of gas pressure and incremental increases of fan speed at set points throughout the roast. This will help keep you ahead of the ROR curve and allow you some wiggle room to make slight adjustments as the roast progresses. Hopefully it will also help even out the roast color. If still too fast, then next step would be to initial gas pressure.

Not that this is a 1:1 transferrable profile but this will show what I mean with the incremental changes.

https://portal.roastpath.com/publicroasts/index/32652230917250523

To be honest, coffee roasting is half science and half magic. Some days the stars just aren't in alignment and the roast machines and beans decide to rebel. Don't be discouraged, we've all been in that same boat!

Sure appreciate your feedback and sharing! To answer your question, yes I was going for a city+ up to or before a full city roast. Trying to get the flavor I am looking for in this Brazil I feel a 10 minute max roast time and spending a little more time in the last phase.

I read through Scott Rao's book and was trying to figure him out. Being an independent person and find it difficult to ask for help I tried to apply some of his ideas. But with out context a lot of it is just pretext... every situation and every roaster handles different and translating and interpreting his information and ideas takes individual situational application. lots of learning.

I also am struggling a little with air flow. Oh my goodness these roasters suck a ton of air! Which I appreciate but with air removal from a building you also have to replace air. This air that is being replaced affects dramatically how the roasting process goes, humidity and temperature. 1st batch ambient controlled, 2nd batch things change and so on till a stable mix is reached. Has anyone made up a chart or tracked this to the point of producing reliable feedback and how it affects the roast?

If it weren't for my passion and love for doing 1 to 2 pound roasting I would have ordered a 6Kg machine. I really enjoy the small batch capacity of the 3Kg roaster and the power it has to do anything I throw at it. I can still roast very successfully 5 pound batches of the Brazil and everything else, I am very happy with that. It isn't very often I need to roast more that 2.75Kg of green at a time so doing it in 2 batches will work for now. I am pretty sure the beans expanded enough to the point where I won't be able to do bigger batches of this particular bean. I'll have to be ok with that for now.

I'll start off by saying I'm not familiar with that roaster. I have a digital 2k, but also roast on much larger roasters.

How does the coffee taste? I've had mélange'd roasts before that were good. (meaning colors are a bit mixed).

What I would do if I were in your shoes:

1. Increase the rpm of the drum.

2. Increase charge temp to around 400.

3. Increase air earlier around 2:45, but not by much. (a bit more convection) - test with your lighter.

(I've noticed the more coffee I put in the more my settings in Hz change)

4. Try to get a longer middle area (your 24%)

Brazils can be tricky. If it were me, I'd try to make the middle of the roast longer. At the roast level you're at, maybe a 12 min roast is what you need.

Of course, if the quality of your green is super low, it may just be the coffee, or it may be that you've got a mixture of different density green. There's so many factors at play, but I suspect the main thing is that it's rushing through the middle phase, then you've got all this built up energy you can't dissipate because the volume of coffee is so great. The heat runs away from you and you can't cool off fast enough.

I've mentioned several things to test, but realistically you wont know what works until you change 1 variable at a time. I'm around 100 roasts into my 2k and just now have what I feel is a solid baseline profile and have learned how the machine behaves. There are no short cuts to trial and error, and sometimes a "mistake" could be just what you need to get you to where you want to go.

Who knows, maybe your first experiment should be to simply try the same settings with a different coffee and see what happens. Good luck.

I have really appreciated all the feed back and it has helped me understand better all that is going on. Something I should have noted on the roast I posted is that around 6 to 7 minutes is where I lost control of the roast, this was not a successful roast and I over shot the final temperature by about 5 degrees (I was mad :) ). I started out doing what I always do for the 2.75kg roasts and have had excellent success. The green I was roasting was some of the best beans I have ever had from Brazil. A mix of Red and Yellow bourbon Arabica beans and semi washed.

Was this coffee still good? Yes it tasted fine, but not great. In my opinion the coffee should be consistent and uniform in color or I have failed. (Outside of quakers and deformed beans)

I have only just over 400 batches on this roaster and I am finally feeling like i am 'starting' to understand this machine.

I have tried using more air flow or convective heat, interestingly if I use a much higher ratio of air flow this has shown to produce a slightly less even roast at 2.75 kg. why is that?

I have increased drum speed and this has helped out over all.

The flavor of these beans at a roast much over 11 minutes to me tastes blah and baked. Maybe slowing the first part of the middle phase and then allowing for a 12 minute roast? I will try this out.

My theory is that the initial phase up to yellow needs to bring the beans to a very consistent and even bean temperature through out the bean. From the center of the bean to the outside of it. This, in my opinion, is where the roast "spring boards" off of. If it isn't uniform at this point the roast will be off.

Thank you everyone for your feedback and help! Have a GREAT DAY!