Charge Temp

[ronnyg]

Hi All,

I just wanted to clarify what we should be using as charge temp.  I have seen some folks using the ET reading for their charge temp and others use the BT.  Which one is the best for overall results?

Thanks,

Ron

[Johnny4lsu]

I always use BT.. Not sure about everyone else

[dickcoffee]

With the perforated drum, I use the BT for charge temp.  I don't know if it would be different for the solid drum.  I went back and reviewed several of my roasts and I'm not sure it would make a great deal of difference whether I used ET or BT.  When doing a 1 pound roast I preheat to 518 on my BT, drop the beans and hit start on my Roastmaster.  By the time I start reading, the chart typically then shows the BT around 400 and dropping and the ET around 450 and dropping although not as precipitously.  (This is what's interesting to me about the Henry Chang challenge re: the equilibrium point.  I've never tried for it but simply go up then down then back up)

[SusanJoM]

Just as an aside here, I've seen quite a few Artisan profiles which have MET labelled ET. 

If when you read a profile you do not see all three (BT, ET, MET), you need to check whether the ET really is.
You can pretty much tell by looking at the shape of it it, but if you are using that as an indication of charge temp, it might be higher than you are wanting for charge.

[ronnyg]

Yeah I had that experience at first with artisan but I think it was through your (SJM) help on HB that we were able to get the temps squared away.  I was just curious because my ET is always a little lower than BT when nearing a charge and I wasn't sure what temp is more important.  I was charging around 235-240c for a 415g batch on the ET which meant my BT was reading 245-250 if not higher in some cases.

[hankua]

I've been charging 1lb at 356f/180c, which can go a little fast.
(Solid drum-72rpm)

What temps/charge weights are we using?

[ronnyg]

Man I may be way off than, I have been charging around 240C with a TP anywhere from about 1:39-1:45 usually with a 415g load.  Temp usually drops to high 90's to low 100's at the turn with a drying time that lasts a total of 4:45-5min usually.

[Johnny4lsu]

That does seem high, but you must be using less heat to still get a decent length drying.

If you're getting great results don't sweat it.. It would probably be fun for you to play around with some lower temp charges.

[Gregr]

One might have advantages over the other but I think what's most important is that whichever you use you you use it consistently so you can taste the results over a lot of roasts. Personally I use BT (I think most people do), and for most hard beans I'll charge at about 430F/221C (love that temp converter over on the right!). One pound loads, turn around almost always right around 1:40 and dry very close to 4:00, with incredible consistency. Oh yeah- that's with the fan set at about 20%, damper all the way open, stove at 2.5kPa. For Indos and other soft beans I'll charge lower, around 410F/210C with the stove slightly lower. That pushes everything about 45 seconds.

[zivsade]

Hi all.

The charge temp depends on several variables, such as -
Solid vs perforated drum
Bean type
Fan speed

Let me explain -

Solid drum caries more internal heat then the perforated drum and that why it needs lower charge temp to Achieve the same TP (time & temp).

Bean type - high grown bean with higher density needs higher temp to achieve the same TP.
Your general target should be to achieve TP @ ~ 1:40 - 1:50 @ 100C degrees.

Why you may ask? Because nothing really happens bellow 100C and there is no use to charge @ temp that result TP lower than 100C.

My usual charge weight is 450 grams (~ 1 pound) and usually my charge temp for dry proccessed beans is 240C-245C and for high grown beans 5-10 degrees higher for both BT & MET. With the data above I usually hitts TP @ 1:50/108C. Please note that I am using the solid drum now and if I would use the perforated drum I will have to use higher charge temp.

[ronnyg]

I tried a hotter charge today at 265C which gave me a turning point of 136 at 101C which hit my goal of staying above 100C at the turn.  Drying time ended up being 4:45 and FC came in at 9:57 with a BT of 204 which is higher than normal but it was my first time with some cheap Brazilian beans I got on sale to practice with so this may be characteristic of them.  All in all I am pleased with the profile although I would like to have seen FC nearer to 9:00.  I was also able to make it to FC without much input in heat or air but I am always dancing after FC with them to keep the RoR as steady as possible to avoid the sudden drop than rise in the curve at the end.

[SusanJoM]

Basically off topic, but....

Since some of us roast in C and some in F, it  when you post temperatures you could post them in both??? 
The converter there on the right should make it easy.
I've tried converting each number as I read, but it makes it really hard to keep it straight in my head. 

 

[edtbjon]

I've been using Kfir's recommended charge temps (220-230C (430F) for 300g)until today, when I radically lowered the charge temp to around 150C (300F) as recommended by Hankua. (Even though the example below has a charge temp of 178C (350F).)  That made a huge difference for me and it's much easier this way.
There are two benefits here (refering to Scott Rao's commandments). I can now add more (read "enough") energy at the start of the roast and second, it's easier to have a steadily declining RoR without stalling.

Now, I just have to wait a few days for the beans to mature...

About the Celcius/Farenheit issue... I always press the default button in the Phases dialogue. There I get the color fields at 150C/300F for drying point and another border at the typical 1Cs at about 200C/392F.

[SusanJoM]

I just noticed (and maybe I should have noticed before) that you are using the solid drum and the slow motor.  That combination seems to be less common than the perforated/slow or solid/fast combinations.
Was that your original selection or did  you come to it by a process of elimination?

And so, what you (and Hank) are suggesting is powering into the curve rather than coasting down from a high charge?
Just when I was going to try upping my charge temp......Wouldn't you know....:-))))

Susan

[edtbjon]

About the drum speed, I'm not sure if the high 72rpm suggested and implemented by Slickrock is really needed. While I can understand his arguments, I decided to try a slower speed and I think it works. Also, I don't think that there is that much difference in conduction if someone would compare a solid and perforated drum for that aspect. Now, what I've done is not to change the motor. The 72rpm is actually more silent to begin with. I simply use another transfomator (for an HP inkjet printer, which is at 18V instead of 24V, which gives me around 54 rpm to be precise. The benefit is a more silent solution. ("I just love the sound of first crack in the morning..." Sorry, I couldn't hold that one back... )
I also saw some posts on HB where one or a few users were at even lower speeds.

While Scott Rao's "commandments" really are recommendations, I find them very useful while I'm learning roasting coffee in general and the Huky in particular. The suggestion from Hank makes it much easier to manipulate the roast in whichever direction I want. If I'd want to roast for 15 minutes I can still maintain a declining RoR without flat-lining.

Now, the proof is in the cup and I have to wait a few days for that, but this and a couple of other roasts I made this afternoon looks really promising.