Initial Temp Too High

[JonFairhurst]

I received my roaster in the US less than a week ago, and so far, I’m thrilled with the product.

My question has to do with the temperature going higher than the profile in the first minute or so. Should I reduce the preheat power to solve this, is there a different solution, or is this normal?

The details…

My first roasts with 1500-2000m REST beans (90g) were darker than expected with first crack at about 5:50. After some trial and error, I found that 1200-1500m REST at L1.5 was close to my target, with 1st crack at 6:40. The log curve was smooth, except it was too hot in the first minute. From there, I made my own profile…

I made the early temperature of the curve less aggressive. From the previous roast, I knew my dry, 1st crack, and end temps. I set those for 4:00, 6:30, and a 20% development time on my custom curve. Lo and behold, the machine nailed it on my first try at my own profile curve! The roast looks and smells great, but it’s resting now. All that said, the initial log still diverges too hot in that early part of the roast.

Thanks for any feedback you can provide!

[BenN]

You will need to adjust preheat value on profile.

Screenshot 2023-04-14 151549.png (140.29 KiB) Viewed 3140 times

depends on how much you want to lower but play with this value for first phase to follow your profile.
Slightly higher does not have any ill effect.

[JonFairhurst]

Great minds. I'm just now preparing for my next roast, lowered the preheat, and I got the same recommendation. I'll give it a try.

[JonFairhurst]

BTW, here is the log of my earlier attempt with 1200W preheat.

log0012.png (106.71 KiB) Viewed 3123 times

[JonFairhurst]

That was a Guatemalan bean.

I used that up and tried a different Guatemalan bean and it was completely different! I’m guessing that it was a bit old. It was dense but really soaked up heat with the temp all over the place! I kept lowering the curve, but the key seemed to be lowering the overall temp. My last attempt on that bean still oscillated, but at least it wasn’t so wild and unstable.

My takeaway is that tweaking the curves is all good, but to really nail it, the preheat and overall temps are just as important.

[BenN]

My most goto profile with 100g load is preheat set to 950.

It still go lite above is some beans but again not that big issue for this initial stage.

[ecelis]

I'm also in the US and so far most of my 100g roasts done at L3.0 to L3.5 have resulted in very dark beans... I guess I should also lower the preheat around 950 for most of the profiles?

[BenN]

Kaffelogic's profiles are developed for 120g load unless specified, you nay end to adjust profile curve, not just preheat.
I can't tell how much to put for transform tool, but may be studio companion doc has some more info.

all beans and profile combo result differently.

[ecelis]

Ben, Thanks for the clarification. So I should try to roast 120g to get best results? If I roast 100g or 70g, without modifying the profiles I should expect to get darker roasts?

[BenN]

it could be. you can also try down the level but I think better try 120g load.
again all depends on beans and profile of your choice.

best to see by yourself.