I have been roasting an Indonesian Blue Bianca starting with the 1200-1500 Rest profile, however the roast temp is below the profile for the first 30sec and then overshoots and doesn't get back until about 2min 20sec. Removing the Zone 1 boost doesn't really help and I have tried putting in a corner which also doesn't do much.
The profile turns quite sharply from about 10sec to about 30sec so I am wondering if the overshoot is due to an exothermic reaction from the beans, whether it can be corrected to follow the curve at this early stage of the roast such as by use of a negative boost, and whether it really matters as it all occurs well before the development stage.
I have had a similar effect with some other beans, so wonder if I should be trying to get the roast to follow the profile more closely in the early stages.
Overshooting Profile Curve
Re: Overshooting Profile Curve
It's easier to help you if you post a log or a screen shot (you will find it under "Tools" where you can capture and save an image). Generally it's not important what happens with the "curves" that early in the roast.
Re: Overshooting Profile Curve
log0272.pdf- (156.82 KiB) Downloaded 137 times
Preheat is 1200. What I am wondering is if I increase preheat to follow the start of the profile more closely, can I then put in negative boost or a corner that early in the roast to reduce the overshoot from about 30sec to 2m15s?
Re: Overshooting Profile Curve
Hi Ross,
Yes now I understand what you mean! I have used that profile also a while back and I had the same overshoot. I think the coffee tasted ok though. I mainly roasted for espresso by then and darker. Today I mostly roast lighter and for filter coffee.
I checked the profile (and the other "altitude" profiles) and something seems a little strange and may be a bug. The preheat is 1200W. That is the same as profiles meant for higher elevation beans and it's more than the 2000-2700 profile! I haven't analysed the rest of the curve that could compensate. Harder beans and smaller beans from high elevations needs more heat in the beginning of the roast.
Anyway I'm quite sure the overshoot comes from the high preheat. I compared two logs with the same Ethiopian high elevation bean. One with 1500-2000 Rest and one with 2000-2700 Rest. The former has a preheat of 1200W and the later a preheat of 1050W. The former has the overshoot and the later has not!
The important thing is the taste though. How did it taste? You could try with different preheat but the roast degree should be about the same to be able to make a fair comparison. Do you find that the bean is scorched outside with the high preheat? Usually they say that much heat in the beginning of a roast is good and especially beans from high elevations that can take that heat. Beans from lower elevations may not and can be scorched and that affects the taste. They may need a more kind treatment.
I wish you happy roasting!
Per
Yes now I understand what you mean! I have used that profile also a while back and I had the same overshoot. I think the coffee tasted ok though. I mainly roasted for espresso by then and darker. Today I mostly roast lighter and for filter coffee.
I checked the profile (and the other "altitude" profiles) and something seems a little strange and may be a bug. The preheat is 1200W. That is the same as profiles meant for higher elevation beans and it's more than the 2000-2700 profile! I haven't analysed the rest of the curve that could compensate. Harder beans and smaller beans from high elevations needs more heat in the beginning of the roast.
Anyway I'm quite sure the overshoot comes from the high preheat. I compared two logs with the same Ethiopian high elevation bean. One with 1500-2000 Rest and one with 2000-2700 Rest. The former has a preheat of 1200W and the later a preheat of 1050W. The former has the overshoot and the later has not!
The important thing is the taste though. How did it taste? You could try with different preheat but the roast degree should be about the same to be able to make a fair comparison. Do you find that the bean is scorched outside with the high preheat? Usually they say that much heat in the beginning of a roast is good and especially beans from high elevations that can take that heat. Beans from lower elevations may not and can be scorched and that affects the taste. They may need a more kind treatment.
I wish you happy roasting!
Per
Re: Overshooting Profile Curve
I’ve tried increasing the preheat and removing the Zone1 Boost, but it still logs below the profile at the start of the roast and then overshoots even further after it crosses the profile curve which was the reason I asked about the use of negative boost or a Corner this early in the roast. The coffee however tastes good, although I wouldn’t say I have a particularly refined palate! I must say I have never had a bad roast from the Kaffelogic, although I roast almost exclusively for espresso.
My thinking was to try to get the roast to follow the profile as closely as possible and preferably keep the log from dropping below the profile curve, so the heat needs to be reduced much more once the roast progresses to the sharper curve in the profile, but even when the boost is removed and a corner put in the heat only drops to around 700W. This might be due to something else in the settings, but I thought it would need to drop quite a bit lower for the log curve to change as sharply as the profile curve.
My thinking was to try to get the roast to follow the profile as closely as possible and preferably keep the log from dropping below the profile curve, so the heat needs to be reduced much more once the roast progresses to the sharper curve in the profile, but even when the boost is removed and a corner put in the heat only drops to around 700W. This might be due to something else in the settings, but I thought it would need to drop quite a bit lower for the log curve to change as sharply as the profile curve.
Re: Overshooting Profile Curve
Hi Ross,
Did you read my post? The overshoot is because of the high preheat! You can compare two roasts with the profile. One with the original high 1200W preheat and one with for example 1000W preheat and see what happens. Taste them side by side maybe "blind" and see which one you like best. Is the overshoot gone with the lower preheat?
Did you read my post? The overshoot is because of the high preheat! You can compare two roasts with the profile. One with the original high 1200W preheat and one with for example 1000W preheat and see what happens. Taste them side by side maybe "blind" and see which one you like best. Is the overshoot gone with the lower preheat?
Re: Overshooting Profile Curve
I can reduce the overshoot by reducing the preheat level, but it is the very start of the roast that I was concerned about where the logged temperature is below the profile and reducing the preheat puts it even further below, so what I was getting at was if I increase the preheat to keep it up to the steep start of the profile can I then reduce the heating more quickly after about 30sec to get it to stay with the profile rather than overshoot?
General opinion seems to be that it is better to keep it tracking above the profile rather than dropping below it.
General opinion seems to be that it is better to keep it tracking above the profile rather than dropping below it.
Re: Overshooting Profile Curve
Hi
Maybe worth keeping in mind that this a profile that has been created in the software, and the beans may physically be able to follow the curve early on.
I think Chris who developed the roaster said it doesn’t matter in the early bit of curve. I think I may have even asked the same or similar question.
Food for thought.
Cheers
G
Maybe worth keeping in mind that this a profile that has been created in the software, and the beans may physically be able to follow the curve early on.
I think Chris who developed the roaster said it doesn’t matter in the early bit of curve. I think I may have even asked the same or similar question.
Food for thought.
Cheers
G
Re: Overshooting Profile Curve
Hi Ross,
I think you have misunderstood the curves. The lower curve is the ROR curve and it doesn't represent the temperature. It's true that the ROR curve goes beyond and if I remember it was this Chris commented that usually it doesn't matter if this happens in the beginning of the roast.
"What Is Rate Of Rise And How Is It Measured? RoR is the number of degrees per minute (sometimes measured across 30 seconds) by which the temperature of the beans increases at any point during a roast."
If ROR goes lower than in the profile it doesn't mean that the temperature is lower. It means that the progress slows down.
In an earlier post I mentioned two roasts I made the same day a couple of years ago in concession with the same bean but with different profiles. Both are "Rest" profiles but meant for different altitudes. The first one had a preheat of 1200W and the second one 1050W.
The first profile is 1500-2000 Rest with 1200W preheat:
The second is 2000-2700 Rest with 1050W preheat:
Red curve is mean temp and yellow curve is ROR
In the second example with the lower preheat both the mean temperature and the ROR follows the intention with the profile "better". EDIT: The RoR curve of the first roast with the higher 1200W preheat could actually be called "better" as it follows the profile one minute earlier than the second profile. It has a greater overshoot but that doesn't probably matter that early in the roast! In your case RoR follows the profile after a little more than two minutes. If the taste of the coffee is OK then I think you shouldn't worry much about it. The end temperature seems to be around 225 degrees so it's on the dark side. You can get much more info of your roasts if you mark them to be showed especially from the very important developing phase End edit.
My taste notes for the first was: "Taste: 12 hours:"Creamy" first taste. Viney. Little grapefruit.
70 hours: Too acid for espresso."
My taste notes for the second was: "Taste: 12 hours: Citrus acidity, floral tones, viney, some body, some chocolate aftertaste. Rather acid, less than 12 hours,some body, some chocolate aftertase, drinkable
84 hours (3½ day). More balanced citrus acidity, floral tones, some body, Mokka aroma. Fresh.
This is 2 1/2 years ago and I was all in for espresso and I was very new with the roaster. I didn't make a regular "blind" cupping or tried them as filter coffee. But it seems as I preferred the second roast better. I may have cheated myself though because of the looks of the curves! Taste is subjective and should ideally have been made "blind"!!
What's important is the taste!
I can see Ross that you are serious about this! Go on and I wish you happy roasting!
Edit: Note that I have a different scale on my ROR curve. It's set at X5 to more easily see what's happening.
I think you have misunderstood the curves. The lower curve is the ROR curve and it doesn't represent the temperature. It's true that the ROR curve goes beyond and if I remember it was this Chris commented that usually it doesn't matter if this happens in the beginning of the roast.
"What Is Rate Of Rise And How Is It Measured? RoR is the number of degrees per minute (sometimes measured across 30 seconds) by which the temperature of the beans increases at any point during a roast."
If ROR goes lower than in the profile it doesn't mean that the temperature is lower. It means that the progress slows down.
In an earlier post I mentioned two roasts I made the same day a couple of years ago in concession with the same bean but with different profiles. Both are "Rest" profiles but meant for different altitudes. The first one had a preheat of 1200W and the second one 1050W.
The first profile is 1500-2000 Rest with 1200W preheat:
- 200906_Eth.png (75.36 KiB) Viewed 1735 times
- 200906_EthAmaro_Gayo_2000-2700Rest.png (73.45 KiB) Viewed 1735 times
In the second example with the lower preheat both the mean temperature and the ROR follows the intention with the profile "better". EDIT: The RoR curve of the first roast with the higher 1200W preheat could actually be called "better" as it follows the profile one minute earlier than the second profile. It has a greater overshoot but that doesn't probably matter that early in the roast! In your case RoR follows the profile after a little more than two minutes. If the taste of the coffee is OK then I think you shouldn't worry much about it. The end temperature seems to be around 225 degrees so it's on the dark side. You can get much more info of your roasts if you mark them to be showed especially from the very important developing phase End edit.
My taste notes for the first was: "Taste: 12 hours:"Creamy" first taste. Viney. Little grapefruit.
70 hours: Too acid for espresso."
My taste notes for the second was: "Taste: 12 hours: Citrus acidity, floral tones, viney, some body, some chocolate aftertaste. Rather acid, less than 12 hours,some body, some chocolate aftertase, drinkable
84 hours (3½ day). More balanced citrus acidity, floral tones, some body, Mokka aroma. Fresh.
This is 2 1/2 years ago and I was all in for espresso and I was very new with the roaster. I didn't make a regular "blind" cupping or tried them as filter coffee. But it seems as I preferred the second roast better. I may have cheated myself though because of the looks of the curves! Taste is subjective and should ideally have been made "blind"!!
What's important is the taste!
I can see Ross that you are serious about this! Go on and I wish you happy roasting!
Edit: Note that I have a different scale on my ROR curve. It's set at X5 to more easily see what's happening.
Re: Overshooting Profile Curve
Thanks for that. My conclusion from all this is that it doesn't matter much if the roast drops below the profile at the start of the roast, so it is probably better to drop the preheat so it doesn't overshoot the curve too much after a minute or so and is following the curve well before we get to first crack. I was roasting on a cheap rotisserie oven before I got the KL, with very crude temperature measurement and relying mostly on colour, but was still getting quite acceptable roasts, to my palate anyway. Having all this data and accurate temperature control has got me over-thinking the issue! It is only some beans I have been roasting which seem to have this characteristic, mostly they follow the curve quite accurately once I have fine tuned the preheat setting, and it is fantastic to be able to repeat the roast consistently.
Hoping my new glass chaff collector and Boost turn up soon, then I'll have a whole lot more to worry about!
Hoping my new glass chaff collector and Boost turn up soon, then I'll have a whole lot more to worry about!