For the lightest brewing roast, stop as the first crack winds down. Pick the moment as follows: during the first crack, you will smell a vinegary and grassy aroma coming off the beans. Stop as soon as that stops -- this is the lightest usable roast. If you do not dry the beans well, this will happen as the second crack starts. If you spend three to four minutes ramping the beans up to 300F (measure where the air exits from the bean mass), you will be able to stop roasts right at the end of the first crack.

For espresso, if you have a proper drying period, you can stop just before the first pops of the 2nd crack, when you start smelling caramel. If the drying period is short, you need to go to the beginning of a rolling 2nd crack.

As you see, a long drying period does not help for full city roasts and beyond, but it stretches out the range of useful lighter roasts. The advice to newbie roasters to take brewing roasts to the first pops of the second, and espresso roasts to a rolling second, is based on getting the beans into the comfort zone of air roasters that heat up too quickly for light roasts.

A longer ramp from 300F to first crack will accentuate the woody, bready, nutty and malty flavors at the expense of sweetness. If you like flavor notes akin to barrel aging wines or spirits, this is not a bad thing to try. You also need the right sort of coffees, Indonesians and Bourbon cultivars usually work. But if you want a lot of acid and enough remaining sweetness to balance it, e.g. you are roasting a fruit bomb coffee like a Sidamo or Hue-Hue, going through this part of the roast fast is your best bet.

I see. Thanks for the clarifications, Jim. I appreciate you taking the time to respond. I roasted tonight with this in mind (5 min drying phase to 300 and then a fairly quick ramp to 1C at about 8 minutes. Done in 11.5 minutes at the first sign of second crack. In a couple days, I hope to see if this has helped).

I tried to pay closer attention to the smell as you described but frankly, it just smells like popcorn and bread crust above ~350F to me at this point. This is something that hopefully comes with a bit more roasting experience.

Jim's advice is sound, to be sure, but also take into account how your roasting setup is unique and may not register temps in lock-step with what is provided. IMHO it's more important to get consistent readings for your setup than it is to shoot for any suggested temperature target. If you are consistently hitting 1C at 375F regardless of bean load, regardless of how close you move the HG nozzle, then you know that's how your setup behaves. Plan accordingly. This is the double-edged sword of a DIY setup - there's a lot more "Your Mileage May Vary" involved, and experience will be your best teacher.

Also, bear in mind that it may take a LOT of roasts to get in the ballpark of "consistent" & "acceptable". That 8 lb. "sampler" pack? It'll be gone in a week. You'll be playing with bean loads, charge temps, ramp tweaks and so many other variables that can easily consume your first 30+ roasts. The DIY path is NOT for people who want immediate & good results. Consider the subjective tone of anyone who tells you that you can get "great" results "immediately" with a DIY setup. I continue to have a great time learning on my HG/BM and can produce results to my satisfaction (and have the ability to tweak heat input to play with profile times), but it's taken almost a year to reach this point and I've roasted, drank and burned through almost 60 lbs. of green, in addition to regularly calibrating my tastebuds against some well-regarded local roasters. Then again, I may be a slow learner .


*throws 2 pennies into the pond*

-s.

Whale wrote:Wouldn't the release of vapor be considered exothermic?

As you stated the energy is stored in to heat moisture and when the vapor is released, the energy is released as well. This is an exothermic reaction. Is it not?

In the case of liquid water turning into steam the answer is no. This is a physical transformation, not a chemical reaction. Burning of coffee beans is an example of an exothermic reaction where carbon compounds combine with oxygen to form carbon dioxide and water,releasing heat.

Sherman wrote:Jim's advice is sound, to be sure, but also take into account how your roasting setup is unique and may not register temps in lock-step with what is provided. IMHO it's more important to get consistent readings for your setup than it is to shoot for any suggested temperature target. If you are consistently hitting 1C at 375F regardless of bean load, regardless of how close you move the HG nozzle, then you know that's how your setup behaves. Plan accordingly. This is the double-edged sword of a DIY setup - there's a lot more "Your Mileage May Vary" involved, and experience will be your best teacher.

Also, bear in mind that it may take a LOT of roasts to get in the ballpark of "consistent" & "acceptable". That 8 lb. "sampler" pack? It'll be gone in a week. You'll be playing with bean loads, charge temps, ramp tweaks and so many other variables that can easily consume your first 30+ roasts. The DIY path is NOT for people who want immediate & good results. Consider the subjective tone of anyone who tells you that you can get "great" results "immediately" with a DIY setup. I continue to have a great time learning on my HG/BM and can produce results to my satisfaction (and have the ability to tweak heat input to play with profile times), but it's taken almost a year to reach this point and I've roasted, drank and burned through almost 60 lbs. of green, in addition to regularly calibrating my tastebuds against some well-regarded local roasters. Then again, I may be a slow learner .


*throws 2 pennies into the pond*

-s.

That's the truth! I just bought a 4 pound sampler pack and am almost through it already. I'm also seeing that even with a relatively small batch size, I probably need to roast through at least a pound of something just to figure out where it should be roasted, let alone tweaking the roaster. I should probably be buying bigger bags of beans.
I do have to adjust the temps most people talk about. I think I'm measuring air temp more than bean temp (or my thermometer is off). First crack usually comes at about 450F in my system.

Sherman is right about temperature measurements -- the first order of business is getting ones that are useful, not necessarily ones that are true. To be useful, they need to

• rise monotonically (i.e. no dips) as the beans heat (at least after the initial drop in/warm up)
• be at roughly the same temperature for the milestones -- brown beans, first crack, first pops of second -- roast after roast. But be aware the second crack comes at lower temperature in slower roasts.

In practice, your measurements are some weighted average of the beans' temperature, the heating device's and the ambient air's. As long as the weighting and your roasting procedures remain consistent, you're in business. If you reposition the sensor, the weighting changes, and the new readings do not compare to the old (although they can be better). If you change the heat gun settings or distances, it's the same story. In short, do not expect that the milestones will remain the same if you tweak your roasting setup; and give yourself ample time to judge the results of any roasting changes.

another_jim wrote:In practice, your measurements are some weighted average of the beans' temperature, the heating device's and the ambient air's. As long as the weighting and your roasting procedures remain consistent, you're in business. If you reposition the sensor, the weighting changes, and the new readings do not compare to the old (although they can be better).

Which brings my question: Where should I put that bean temperature sensor? My only reference for the question is the picture that Jim has posted on the Quest M3 thread

(Another airhead drums: Initial Impressions of the Quest M3)

In the M3 it seemed that the sensor was indeed inside the the drum but would only contact the beans occasionally. Given the fact that the drum is rotating there is not that many practical points, but I was thinking that the "ejection door" (for lack of the actual name) could be the spot where there would be the most actual contact with the beans.

Is this contact with the beans important? Can I correlate an internal temperature of the drum to a beans temperature?

Disclaimer: I am just starting the preparation work. I have not started to roast yet but I am gathering "stuff" so a little understanding of the actual important factors will help me.

If you feel that I have not read something that I should have, please just post a link and I will read on.

People contemplating home roasting have to decide exactly what it is that they want to accomplish.

This is such an important statement that I chose to put it in bold, italicized type.

If your goal is to get the sort of professional results that the most respected roasters obtain, with their ultra large and expensive equipment, then that goal is simply and clearly out of reach for 98% of the people who will home roast. In order to get that sort of result on a consistent basis you can just about forget using any of the popular, relatively inexpensive home roasting devices out there. You will either need to start with something at the upper end of home roasting equipment, and severely modify it, or you will need to buy professional type roasting equipment that will cost you several thousand dollars on up.

If on the other hand you want to obtain results that vary from acceptable to very good, but which are probably inconsistent, you can do this with upper end equipment, a focus on detail, and a lot of hard work. Home roasters obsess about a lot of detail, much of which they can't really control, and using the sorts of equipment that they own, it doesn't matter all that much anyway.

So decide what you want to accomplish and then go from there. The most accomplished professional roaster in the world would have great difficulty producing world class roasts from a bread machine or a Stir Crazy or a Hottop, or ________________ (you name the popular home roasting device).

This is not to say that you shouldn't home roast, or to say that you should accept that you will produce crap. But it is to say that unless you have the requisite level of equipment, and a lot of time and money you are willing to devote to the process, professional results are going to elude you and perhaps the focus should be more on getting good to very good results, with reasonable consistency, then it should be on some pipe dream that if only you can control your measured temperature to within 0.01C, that the results will magically appear.

ken

On Ken's post: This is somewhat inaccurate. It's not about the professionalism of the roaster, but about the characteristics of the coffee. You can roast some coffees, for some uses, even on the poorest equipment. Harars, Yemens, and Brasils to a rolling second crack, or Indos to a Vienna or French roast, can be done with just about any roaster. Check the homeroaster's list from a few years back, and these will seem like the "best" coffees.

The lighter the roast, or the more acidic bean, the better the gear has to be, to get the most out of the bean, i.e. a roast sweet enough not to flatten out the highlights that make that bean distinctive. Very few professional roasters, even among the very best, push this envelope; since most of their customers expect coffees that taste like coffee, i.e. medium roasts with lots of caramels and roast flavors. For espresso only, I could probably get away with less expensive gear and less measurements; the timing and precision constraints for roasting an auction coffee for brewing has the toughest constraints.

On Sylvain's Post: When youy measure temperature, you measure the air. To get a good value for a bean temperature measure, you are looking for air that is as close to the bean temperature as possible. By simple physics, this is the air that has been in contact with the beans as long as possible. So don't put your sensor insiude the bean mass where the air is entering it; put it in the spot where the air is just leaving the beans or has been in contact with them for longest.

In an air roaster, this is simple. You place the sensor just above the surface of the beans, where the air is exiting the mass. In a drum, this is usually close to the center of the drum (relative to the vertical view), and towards the end of the drum where the air is exhausted, which is usually the front, but not always. Sherman is still trying to figure out the airflow in a bread machine/heat gun set up. For those using a heat gun and dog bowl -- how good is your nose?

Thank you Jim.

I am looking at a setup with solid drum (sorta similar to the M3 but more archaic), thus the idea of the lower front portion of the drum where the door is to locate the sensor; most contact with beans but not necesseraly most contact with the air that has been in contact with the beans. The exhaust is forward and up, so the air flow will be minimum at the lower front portion of the drum.

Am I misunderstanding something?