Bumpy ROR (among other issues) - Page 2

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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Postby hankua » Jan 10, 2019, 2:06 am

Evan is spot on. I would suggest finding a low air setting by removing the exhaust pipe and using your hand to feel the air pressure. Are you getting some air flow at 1? Whatever the low point is I'd increase it a bit, say if low is 1; use 2. And leave it there for the entire roast until first crack begins. Looks like you have a window to see the exhaust, increase the air just enough so the smoke is coming out nicely from the pipe. The idea being your running the roast using the gas knob until you get some solid results, and then add in more air adjustments.

Another thing you can play with is to set the gas and air on a medium setting and idle the machine at a fixed temperature (without beans). What happens when you increase the gas, or the air? All of that changes with green coffee in the drum, but it doesn't hurt to get a feel how it operates. At least you can find a warm-up setting where the time corresponds with your preferred charge settings.


Postby eltakeiteasy » Jan 10, 2019, 12:35 pm

Almico wrote:I haven't done my first drum roast yet, but am about to any moment.

It appears to me that your initial RoR could be stronger. You seemed to have warmed it up enough, so maybe try a smaller bean charge. Most roaster mgfs overrate their products' capacities.

Not sure why you ET is dropping off a cliff. No Bueno. I picked this up from Scott Rao's recent blogpost:


Notice the gas settings at the bottom. He recommends gradually reducing the gas.

This is great info, Alan! Would you say this correlates to a fluid-bed roaster as well as far as heat instead of gas? I have been going up with my heat as I roast. Perhaps I should start at 80% ~4000F and then slowly decrease as the roast proceeds as Scott shows?

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Postby Almico » replying to eltakeiteasy » Jan 10, 2019, 1:09 pm

Increasing heat during the roast is a recipe for disaster.

Fluid bed roasters, at least mine, have a saggy RoR curve due to the fact that hot air leaves the roast chamber as soon as it enters. There is not much you can do about it. Increasing the heat as the roast goes along will make for a better looking curve and bad tasting coffee.

Best practice is to build heat momentum into the bean up front as much as possible. Air roasters can do this more gently than drum roasters. I try to hit 300* between 4 & 5 minutes and keep the BT curve charging up through Maillard. This builds pressure inside the bean; the result being the coffee develops faster due to the pressure cooker effect. Depending on the bean, you can usually drop sooner while having a more developed roast.

I don't believe one roasting method is better than the other; they each have certain advantages. The trick is to maximize the advantage of your air roaster, and dragging out a roast for 15 minutes is not the way to do it. Get the coffee in and out as quickly as possible with declining heat while still getting full development.


Postby eltakeiteasy » replying to Almico » Jan 10, 2019, 1:42 pm

Great info thanks. I will give this a try next roast. I tried this my very first roast and ended up with a ROR all over the place from adjusting the temp. I set the start temp to ~360* which it hit around 5 minutes but then I had to add heat to bring it up to 415* for the finish temp. If I set the roaster too high to start I hit ~360* WAY too quickly:


As you can see from my background I was striving for something more like this:


Source: https://www.perfectdailygrind.com/2016/ ... UGF1UmNclA


Postby edpiep » replying to eltakeiteasy » Jan 10, 2019, 2:36 pm

So it seems you had PLENTY of momentum in that roast. Those BT ramp specs in the DRY stage are really high. I am curious as to what kind of cup profile you wanted and how that roast measured up to those expectations. The fact you spent that long in the development stage seems you were looking for a pretty dark roast am I right?


Postby eltakeiteasy » replying to edpiep » Jan 11, 2019, 5:42 pm

Hey Evan,

Thanks for the response. I roasting that one for a friend who likes really dark roast. I am not a fan of dark roast (I normally stop within 2-min of FC) so this was my first attempt. I am trying to figure out how to get the momentum needed while backing off the heat to get a slowly declining ROR. This was one my of roast last night (you can ignore the beginning ET as I was experimenting with a new chaff collection system. I also forgot to mark FC and FCe as I was busy messing with the chaff system I just built):