(Hopefully) Useful Home Roasting Tips

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Ken Fox

#1: Post by Ken Fox »

I've been home roasting now for more than 6 years, with almost 5 years experience using variations of my present set up, a 1lb commercial sample roaster:

While I've made steady progress in the quality of my roast product, only in the last few months have I "put it all together" to the point where I'm genuinely happy with my results and seldom disappointed. To the extent that anyone can learn anything about roasting from an online post, I'm hoping that some people may find the following information useful in their own home roasting odyssey. Unlike most of my posts, I'm going to try to keep this brief and will list what I think are the most important points in order of their importance. These points if ignored will probably prevent you from producing a roast rivaling what you might buy from a good roaster, other than by chance.

(1) Use the best green coffee that you can afford for the intended use of the coffee. Not all beans will be good for all uses, but you cannot have excellent results with mediocre beans.

(2) Accurate and reproducible thermometry is absolutely essential to good and repeatable results. The thermometry probe must be located in the same place every time, or your measurements will mean almost nothing. And, you can't just look at the probe readings, you have to act on them!

(3) Final roast temperature is important, however the way that you get to the target temperature is just as important. 440F reached in 10 minutes will not be the same as 440F reached in 15. Some portions of the roast cycle will have more importance than others, and it pays to learn which are which, and you can only learn these by experience and by tasting your results!

(4) The speed of temperature increase that yields the best results will probably NOT be a constant uphill slope at the same velocity. There are at least two different portions of the roast that deserve different treatment. In my roaster, my experience is that the impact of what I do before first crack has markedly different results than what I do after first crack starts and before the roast is terminated.

(5) The natural tendency is to want to have things "happen," e.g. to experience first and second crack, but your best results might come from terminating the roast at a lighter roast level, e.g. before the onset of 2nd crack. In order to do this, you are going to have to learn the thermometry of your roaster past the onset of 2nd crack, in order to anticipate it and to end the roast before it starts.

(6) You must approach roasting as though it is a necessary skill that must be mastered in order to become a "complete coffee person." There is nothing that I do with coffee that has as much of an impact on the drinks I make, as the quality of the raw material I use, e.g. the roast products. Everything else, including barista skills, espresso machine temperature stability, grind setting, you-name-it, pales in comparison to what you produce as a roaster. If you approach roasting as a PITA (which I used to do) you will get only so far as a roaster and no further. If you constantly evaluate what you are doing by the criteria of your results, you can continually progress. In the end, equipment and beans permitting, you should get results that are good enough to rival a good commercial roaster, but these sorts of results do not appear out of thin air, they require a lot of effort on your part.

(7) Get in the habit of weighing your roast product, and comparing the before and after weights of the green and roasted coffee. You can learn a lot from this, and it will help to keep your roasting style more consistent. If you have a batch where there is a big difference in the weight loss, this points to the likelihood that something has changed -- either the beans themselves or something that you did.

As an example of number 6, above, I performed a little experiment with my roasting before Jim Schulman arrived for his most recent visit this past summer. I took several coffees and roasted them all in 2 different ways, to the same final temperature but with either 2.5 minutes or 4 minutes between the onset of first crack and the end of the roasts (e.g. the speed of temperature increase after first crack was altered). I hadn't always been consistent in the length of this "intercrack" period and wondered what impact it had. The results were extremely obvious; the 2.5 minute interval produced dull coffee that was usable only if disguised in milk. The 4.0 minute interval produced some of the best results I've ever had. We compared simultaneously made shots from these two types of roasts (same beans, other parameters constant) in a blind tasting fashion and Jim and I both picked the slower (4 minute vs. 2.5 minute interval) coffees 100% of the time. It was that dramatic, but I would never have learned that without testing it.

Here is a description of the roasting parameters that work best in my equipment and may or may not work well in yours. Even if my parameters don't work for you, knowing that these parameters exist may help you to experiment a bit with altering them in order to find what works best for you. I have a drum and therefore if you air roast you will need to extrapolate to your particular set up, as the processes are different even if the results can be similar.

(1) Drum is loaded when the air drum temperature is around 350F

(2) Precisely weighed bean charge load of 454g is used every time. You will need to determine what is the best charge weight for your particular roaster. With my roaster, using 500g rather than 454g (1lb) produces distinctly inferior results, presumably due to unevenness of the roast.

(3) The very beginning of first crack is reached at 8 minutes, never much less and never more than 9 minutes. The speed of temperature rise is not terribly important but needs to be relatively constant and adjusted during the process in order to meet this timing.

(4) The heat needs to be reduced as 1st crack approaches and is reduced further after the onset of first. There is generally a period shortly after the onset of first crack where the temperature does not go up much or may even remain constant (BUT DOES NOT DROP) for a period of up to 1.5 or possibly two minutes.

(5) I roast almost to but never past second crack (your taste may differ), and I try to keep the interval between onset of 1st and what would be onset of 2nd at around 4 minutes, never more and never less than 3.5 minutes.

This roasting paradigm has yielded the best results I have ever had for use in espresso (but also for drip, which is a secondary usage). The results appear to be highly repeatable. The weight loss percentage that I find with these roast parameters is around 16%.

You cannot have good and repeatable results in the absence of good thermometry. Roasting is not a spectator sport, it demands your constant attention if you are going to get the best possible results.

Hope this is useful to at least a few people.

What, me worry?

Alfred E. Neuman, 1955

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Randy G.

#2: Post by Randy G. »

Thanks for taking the time to put all that together, Ken. There is a lot of really great information there which can help folks advance in their roasting quality. One of the facts that rang so true with me is the extension (control) of the time between first and second which I was not able to experience until I got a roaster that was controllable.

For years I tried to convince Hottop that user control was critical, and their last two models (the P and B) seemed to reinforce that, giving me the best coffee of any of their roasters. Although the amount of time it takes to reach first is somewhat limited by the power of the heating element, being able to lower the heat at the onset of first to extend the time between the onset of first and beginning of second has dramatically improved my roasts.

I intend to use the info you put together to try to move to the next level of my roasting.
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Matthew Brinski

#3: Post by Matthew Brinski »

Ken, thanks for putting this up. You're the man ... even if you don't like the GS3.

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#4: Post by Martin »

Thanks, Ken
Excellent post! Both the specifics and the degree to which they are generalizable to other methods----and mine are about as far from yours as can be imagined. For example, I use no thermometry. I can't be bothered, and I do fewer than 3 roasts per week (under 12 oz) and I'm constantly playing with varieties and blends. The result, undoubtedly, is that my roasts are not as consistently optimal as yours. Doesn't matter! There's still much in these 7 "big" points and 5 parameters that translate to my experience.

Did I mention that I also appreciate the years of your posts and what they have contributed to the way I think about coffee? Consider it mentioned.


Ken Fox (original poster)

#5: Post by Ken Fox (original poster) »

Matthew Brinski wrote:Ken, thanks for putting this up. You're the man ... even if you don't like the GS3.
Where'd you ever get that idea?

If I didn't already own 2 commercial home machines, and were in the market for an espresso machine right now, the GS3 would be very high on my short list. The only negative is that it is a bit new, and I prefer more mature technology, as I have a fairly limited toleration for problems with equipment.

What, me worry?

Alfred E. Neuman, 1955

Matthew Brinski

#6: Post by Matthew Brinski »

Ken Fox wrote:Where'd you ever get that idea?
It was a comment made in jest since you never jumped on the "must have GS3" bandwagon (which I do understand your views from following your previous posts, and I also understand that you do regard it as a quality machine).

Seriously though, the information you and Schulman put up is great. Why don't you guys just write a book already?

Ken Fox (original poster)

#7: Post by Ken Fox (original poster) replying to Matthew Brinski »


You are extremely kind.

I think your comment, while true for Jim, is a bit much as applied to me. I do a fairly good job of testing other peoples' ideas, but unlike Jim I seldom come up with an original one.

What, me worry?

Alfred E. Neuman, 1955


#8: Post by Rainman »

Ken- thanks for "spilling the beans" with your procedure. That's fairly similar to the parameters I use in my sc/to and what I hope to approximate with my USRoaster 1 lb roaster when it arrives (hopefully in another month or so). I realize different roasters will differ a bit, but I'm hoping not to have to deviate too much from what I've nailed down already. Going from electric/convection to LP gas/fan has me wondering just how much different it will be, though. I'm still debating the thermometry and data logging equipment, and I'm going to wait a bit after playing with the roaster before settling on a unit (likely either a Fluke or Picotech)-- I just want to get a little physical familiarity with this thing to see if I can produce successful roasts with it, then start recording temp curves to gain better consistency.

Thanks for the tips.


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#9: Post by Fullsack »

Ken Fox wrote:(1) Use the best green coffee that you can afford for the intended use of the coffee. Not all beans will be good for all uses, but you cannot have excellent results with mediocre beans.

To take this a step futher, pick the defects out before roasting. Insect damage, fungus damage and broken or chipped beans can give your roast a dirty, sour or moldy flavor. These little varmits were plucked from only 225 grams of a blend supplied by a well regarded purveyor of green beans for home roasters.

Advantage home roasters: we have the time to do this kind of thing.
LMWDP #017
Kill all my demons and my angels might die too. T. Williams

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#10: Post by mrgnomer »

Thanks for sharing your experience, Ken. I've just been getting used to the roast control with a Hottop programmable and your points not only agree with what I'm experiencing I really think they'll help me better roasts.

I had an iRoast2 for about 3 years before the Hottop. The Hottop I've had for about a year now. I'm noticing there's a stage between about 370F to 390F depending on how steep the heating ramp is to that temp where there's a sweet smell that comes out. I never noticed it with the iRoast but it's very noticable with the Hottop. I'm assuming this is a caramelization stage. It's just before the start of 1st crack. I've tried reducing the heat to extend the smell/caremilazation(?) with mixed results. Into 1st crack I normally get the heat up to 100% for fear of stalling the roast if I don't keep the heat ramping up.

I'd really like to preserve that sweet smell in a roast to bring it out in a good espresso extraction. My rest from 1st to 2nd has been very short; usually under 2 min. From your points it looks like backing off on the heat at the start of 1st crack should bring the chamber temperature down to extend the rest without stalling the roast in 1st crack. You think I could get sweetness to come out more with a longer rest to 2nd?
LMWDP #116
professionals do it for the pay, amateurs do it for the love