Hi all,

I'm having a little difficulty achieving a light roast using my Toper. I've tried multiple charge temps, flame settings, air flows etc but I can't achieve a light roast without being completely under developed.

Attached is a generic profile that I might use. It's 2.5KG batch in a 3KG machine.

Any sugguestions?

I know firstly you will say that is way too hot to begin with, but I've tried charging with the drum at 120c with 2KG batch and flame at 100% but there's not still not enough power to get it going so result in 12min fc (result is a medium).

Thanks
Charlie

I would try reversing your gas rates at beginning and midpoints, i.e., 50% to start, 75% at bean yellow, then take it down around the beginning of FC. This gives you plenty of steam heading into FC. And depending on the varietal, you can charge pretty high without hurting the bean. I've found that tipping and scorching occur during or after FC, when the bean structure is fragile and complex caramelization is going on. Also consider not so much airflow, if this is one of those roasters that passes ambient air through the drum. I have a Diedrich, and I almost never go with 100% through the drum.

Thanks, I'll give it a shot now..

Okay tried it. Seems fractionally lighter, but still got quite far to go. I took the airflow to just 50%. Do you turn the burner off before the end of the roast? I never do, hate seeing those numbers drop with coffee still going around.

You should have enough airflow throughout the roast to keep negative pressure inside the drum. I can't tell you what percentage of fan speed/damper setting it's going to be, but can tell you how to determine it.

Real time plotting/logging software will make your life a great deal easier than data logging alone. Having roasted "sights, sounds and smells, for years, I didn't understand what a difference real-time BT temperature graphing made to the profiling process until using it for a few months, and cannot recommend it too highly.

If you get an FC finish at a drop temp of 186C, your listed temperatures are unreliable. For now, you need to attach roast milestones to your numbers so we have an idea of what's going on -- but you really should fix your thermometry to get a better picture.for yourself. At least note the roast events at their particular temperatures so we have some idea of what's going on.

A lowish drop temp (low enough to prevent scorching of honey and natural process beans, for instance) should not be an impediment to finishing the first interval -- (accurate) 150C BT, "Drying," "EOD," "Yellowing," "Cat Face" -- within 5:00 or less. If not, your roaster needs maintenance.

You're "ideal" profile is completely opaque. I can see what you're doing, but not what you're trying to do. Write (or better yet, plot) your goals; and use the gas to achieve them. Then the question becomes simply whether you have enough power and agility to achieve your goals rather than trying to impose some sort of gas/air use strategy.

On what bases are you currently choosing your airflow and gas settings? Other than as curves which progress from lower to higher (and vice versa) over time, they make no sense to in terms of RoR management. Airflow means little if you're not getting the right RoR. The roast master may need more adjustment than the roaster.

As you know, FC -- border of 2d Crack -- is not a light finish. It's well and truly medium. C -- end of 1st, ~208C - 210C in real temperatures -- is on the light/medium border; and it's where I'd start. 5, 5, 2 is a pretty good profile for a lot of brightness with some depth. I prefer breaking the profile into 6:00, 3:45, 2:15 because the slower Drying, faster Ramp, slower Development loses a little brightness but picks up a great deal of sweetness and stores a lot better; retaining fruits and florals for up to a week after resting, instead of losing them the day after the rest.

Rich

Burner off only if I'm sure I have enough momentum to finish without any slowdown in ROR. You can easily bake a batch by slowing down too much at the end. This http://www.coffeeshrub.com/shrub/conten ... -out-roast is an interesting resource re: roast stages and profiling.

barbarblacksheep wrote:Okay tried it. Seems fractionally lighter, but still got quite far to go. I took the airflow to just 50%. Do you turn the burner off before the end of the roast? I never do, hate seeing those numbers drop with coffee still going around.

Charlie,

Gas and air flows are neither abstracts nor absolutes. They are tools.

You need to drop gas and raise air just before the onset of 1stC, so that once exothermia ends the RoR will be correct for the Development you want.

That means knowing the temperature for 1stCs, anticipating it, and making the adjustment 5C - 10C before. How much before, and how much the adjustment depends on a number of contingencies.

One of the best things about real time plotting software is that you can see the inflection point in the middle of rolling 1stC when exothermia ends, and carefully ride the gas to make sure the RoR doesn't fall into stall range.

Rich

Okay I should add some more info:

Using the above profile, I'm getting FC at 10:00 & 180c which is what I'm aiming for. As you can see, I've already dropped the gas well in advance of FC, but still not getting a light roast (it's not dark either, more like a medium/light). During FC, with the gas at 10% it's barely enough to keep the BT going upwards, any less and it would stall.

boar_d_laze wrote:A lowish drop temp (low enough to prevent scorching of honey and natural process beans, for instance) should not be an impediment to finishing the first interval -- (accurate) 150C BT, "Drying," "EOD," "Yellowing," "Cat Face" -- within 5:00 or less. If not, your roaster needs maintenance.

When you say drop, do you mean start/charge? Yellowing stage is usually about 6:30. I can't get that any lower without drastic changes. Which maintenance issues should I check?

By "FC" you mean 1stCs (onset of first crack), not "Full City," and I apologize for not understanding you the first time.

If you're looking for what used be called an "American" roast and is now called "Scandinavian," try dropping during rolling 1stC. If you go all the way through to 1stCe (end of first crack), you'll be at a "City," roast finish. If you drop just after 1stCs, but before going into rolling 1stC, to what we call "New England" in the US, the affect is very bright but unpleasantly high in chlorogenic acid.

If you're going at a reasonable speed (10min to 1stCs is very reasonable), and looking at a real time plot, the roast level you're looking for is probably right at the inflection point in the RoR as exothermia ends during the development period.

The problem does not appear to be with your roaster, but that you're dropping too late for your desired finish.

Rich