Slow start?

[Agrajag]

I've done a few roasts now with my Huky and am having trouble getting the RoR I want at the start of the roast. I'm doing 250g so would have thought that I wouldn't need the gas at 4kPa, but I do, and even then it's a bit slower that I would have thought compared to what other people are getting. Here's a roast I just did:



This was with my new fan controlled in artisan so I've got the fan % but I haven't gotten around to logging the power yet. The 70% fan at about the end of FC was a bit much I think.

I did a pretty long warmup (15-20 mins), ambient temp was 15°C. I had it nearly off until about one minute in, then turned it up to 4kPa until 150°C then started turning it down according to Gregr's guide. 1kPa at the end of FC, 70% fan but that seemed to send BT down so I quickly turned the heat up a bit and lowered the fan.

I'd like to try doing bigger batches but am concerned the RoR at the start would be even slower. What might I be doing wrong or what might be causing this slow RoR? Solid drum/fast motor configuration.

[Agrajag]

Just a note that I was seeing a similar starting RoR with the standard fan with the damper set just open, so I don't think my new fan is doing anything crazy.

[Gregr]

I always roast 454g so I can't give you specific help there- hopefully others can. If I had to guess I would say the small charge weight is playing tricks on you. What I can tell you is that roast is going to taste great. I'd expect heavy fruit, maybe blueberry since it's a Yirg, and I'd be dying to pull shots with it if it were mine   A dry time of 4:21 is in the realm of excellent though maybe a tad fast for a dry process, then again maybe not. 3:30, a pretty fast RoR, in the middle phase should bring out those wonderful Ethiopian origin notes and a 2:30 finish should probably make it work for drip or espresso very nicely.
Regarding the end-of-roast fan and heat adjustments-- studying my roast notes for the last couple years what I see is that if the bean temp RoR/delta is roughly 12F/-1.1C coming out of first crack then having the fan at 50-75% and stove very very low (.5kPa or lower) allows for good development time without a flick. If the bean temp delta is lower than that coming out of first crack either drop the beans earlier to avoid baking or keep the fan low-ish to eek out a little more development then look at the settings and try to adjust for next time (adjusting as far back as a minute before first crack even starts to get more momentum going into first crack).
Using the stove and low fan to bring the RoR back up is tricky to say the least. Can be done but it's sooooo easy to overdo it and end up with roast notes. It's a little hard to tell with your graph but it looks like the bean temp was beginning a steep ramp up when you dropped the beans so you managed to ride that fine line well. I suspect that had you let that roast go on any longer you'd have seen the bean temp shoot up, or "flick".

[Agrajag]

Thanks Gregr that's some very useful information. Great to hear you think this was a good profile and will taste delicious even if it was a bit by accident  I drink mainly espresso so should be good. This bean is actually what prompted me to get a huky as I got some great roasts from it with my behmor (you're right massive blueberry notes), however it was hit and miss, some roasts just lacked flavour and with the behmor's limitations I couldn't tell what was going on.

It's good to know this drying phase ramp will work, however I'm still a little concerned that if I wanted to do a fast start I'd be unable to, so anyone that has any suggestions there would be appreciated.

[Agrajag]

bean temp RoR/delta is roughly 12F/-1.1C

Just a note - you can't convert F to C for rate changes in the same way you convert it for temp. 12F/min is actually 6.6C/min, it's still rising, we wouldn't want it to go negative I've just found this handy page here http://www.warmtips.com/20060711.htm which has a rate converter calculator, maybe a rate calculator could be added to the right side of this forum below the temp converter? Would definitely be useful for me when looking at other people's profiles and trying to convert RoR.

[edtbjon]

There is no info on what type of drum etc you're using. (You can put that in your forum profile.) But I guess from charge temps etc that you're using a solid drum.
There is no note of any fan at all until DE (150C). I used that same approach myself for a while with a solid drum and had the same experience where it seemed like I could add infinite amounts of heat without any reaction. I had developed a scheme from watching an early video/podcast from MillCityRoasters, where Joe Marocco demonstrated his Huky, using no fan in the beginning. But after some 20 roasts or so I abandoned that approach. Much because Joe doesn't use any fan speed control, but uses either full speed or off and uses the damper for "fine control".
I do buy his ideas though. So I found the volt setting on my Variac where I just get a hint of suction (checked with a cig.ligher at the trowel hole) and set the fan around that speed for the roast up to DE. This whiff of air makes the burner much more effective, without really adding any significant airflow to the roast. But foremost, it made the roast much more easy to control.
I know that you have made a "custom" fan solution, which seems very interesting. Just make sure to calibrate it. With that I mean that with a standard AC fan and a Variac, the fan starts spinning slowly at say 50V and starts to create any negative pressure at all at around 75-80V (some 35% of the european max 240V). So I've calibrated my Variac front plate to show 0% at around 70V and then graded it up in 10% steps from that.
I hope that you've got some hints from my ramblings here... While your roasts looks good, I guess there is room for improvement, which is what you look for. You will have ups and downs, but you do have a very good start there.

[Agrajag]

There is no info on what type of drum etc you're using. (You can put that in your forum profile.) But I guess from charge temps etc that you're using a solid drum.

I did mention at the end of my post that it's solid drum, so yes you're right with your guess

There is no note of any fan at all until DE (150C).

It is there but just a bit hidden by the charge temp (I'm trying to find the best way to get artisan to display this information, it's a bit limited in that way), 20% fan speed. I just put my hand under it and "guessed" that that was the lowest that would have an effect, but will try the cig lighter method you mentioned. Your other information gives me some good ideas, thanks!

[edtbjon]

Yes, the info was there. (I often use my iPhone or Ipad with small screens when surfing forums etc... "Well, I gotta blaim something!!!" )
On the roast as such, you're doing good. Ethiopians are in general less uniform than e.g typical washed CostaRicans. That makes (on this concept) 1C with Ethiopians much more spread out than again e.g Central Americans. In my mind first crack usually goes on for about 10-12C, but definitely not for 17C. There usually are some outliers which pop early (quite common) or late but they are really not part of the first crack as such. There are recent threads (Come to think about it, I even wrote an article on it which is in the Downloads section...) on this subject.
Long story short. The very archetype for a light roast is a Yirgacheffe. For your next roast, try dropping the beans at 210-212C for that "typical" light roast Yirga. (If the beans are of good quality of course...)
This "light roast thing" with the Yirgas does not neccesarily (sp?) apply to all Ethiopians. I roasted a "Wild Kafa" (wild grown variety grown not far from the Yirga region) a couple of days ago. That one is thin and boaring unless I touch second crack, where it becomes balanced with a very nice stonefruit acidic note still remaining.

[Agrajag]

Yeah I just didn't press the end of 1C button in artisan. It would have been about when I upped the fan to 70 as I was going by Gregr's roasting guide.

I'm tempted to roast lighter as you say, though I'm roasting for espresso so I'll see how this one tastes and maybe experiment with the next.

Thanks for the tips!

[Agrajag]

One question actually. If you're roasting lighter, do you try to get the RoR after first crack slower so that the total time is the same, or do you just end up with a shorter roast by dropping earlier?

[edtbjon]

One question actually. If you're roasting lighter, do you try to get the RoR after first crack slower so that the total time is the same, or do you just end up with a shorter roast by dropping earlier?

On your profile it looks like you're going into 1C with an RoR of about 10C/min, which gives you room for slowing down a bit. (You do set the approach to this part of the roast up earlier, more or less at DE, so that you don't have to panic, but that comes with the experience with the Huky.) The idea is to strech 1C a bit compared to the roast above, but don't overdo it. I.e you don't want a roast with say 10% of development time, but 15% would be OK.
Let's take the roast above as an example. If you'd lowered the heat by 10% (more) around 170C it would slow down the roast a little bit by the start of 1C.
You will eventually find a way to simplify your controls pattern, i.e create a pattern where you adjust the heat and fan three times respectively. That will come from analyzing the Artisan graphs and see if you could have made those two adjustments in one step instead ... and so on. There's nothing wrong in doing many small changes, but it's hard to repeat for that (illusive) "perfect roast".
About "Roasting for espresso", I know very well what you're thinking. Most roasters do (regardless of level of professionalism...) roast "for espresso". I'm not so sure, even though I don't want my espresso shots taste like biting a lemon slice. Check this article on Joanna Alm (Swedish champion 3-4 times, with good results in the WC's too.): following-the-curves-roasting-insights-from-joanna-alm.

[jyalpert]

FYI I used to get that low initial RoR when I was roasting 227g batches.  I upped my batch size to 350g and now get a more "normal"-looking curve.  Not sure how that translates to the solid setup, but I'd guess something similar might be going on.

[LTB]

Slow start Well I've definitly got a slower start, my RoR during the drying phase is lower !! I think I was trying to slow to much the firt phase, and speed to much the second phase... I will try to go back to something like your profile to taste the difference.