20% Development Time \ % loss \ Roast Level Question

I have a question re: the relationship between development time and % loss.

I’ve read Hoos on 20% dev time being a sweet spot to roast profiles. I also have been really honing in on tracking my start weight - end weight to calculate % loss in determining targeted roast levels.

If I roast FC (according to % loss) then i’m always around 18-20% dev time and am happy to be sure with where those roasts end up and taste. If I roast City/City+ (according to % loss) then I’m usually only around 10% dev time.

Here’s where I am confused. If I stretch out dev time on my lighter roast profiles then they fall outside of the % loss range for City/City+ even if they look like a lighter roast color-wise. Most recently, I was shooting for a City+ Guji and the dev time got stretched out accidentally to about 20% but in the cup the beans tasted baked and dull.

What am I missing here when assessing targets for development time vs % loss?

The big thing I’ve learned is that development time (and time spent in each phase, for that matter) varies based on your desired roast level. For your lighter roasts, you pull a lot of your flavor in your yellowing and caramelization phases; your development phase is not as crucial. For me personally, I don’t follow those specific percentage “sweet spots” because I see it as an ever-moving target based on bean.

I would try another roast where you shift some of that development time to your caramelization/lead-up into development phase. This will give you a shorter development phase, which I’ve found much better for your light roasts.

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So I know that the SCA considers % loss as a way to determine the roast degree as well as color and flavor profile, but I have never met anyone actually use it in oppose to the color. However, it is confusing because am pretty sure i can do dark roasts with lower %loss than lighter roasts simply by maxing out the energy and ending the roast in shorter time, 5 minutes for instances.

As to your confusion, losing coffee mass is a product of time+heat. I speculate that you got light roast and high %loss by roasting for long time with low heat?
and the baked and dull taste was because your dev time was too long? because despite the dev time % ratio, in my experience, dev times over 3 minutes tend to produce this kind of results.

I hope you can share the roast profile in the post for a more clear perspective.

I apologize, but I must say that you got everything wrong. SCA considers % loss as a way to determine the % loss. The roast degree is determined by colour, which in turn is determined with a colour metre. If you max out the energy and do a roast in 5 minutes, be sure that you’ll have a higher % loss than a normal 10-12 minutes light-medium roast. The end temperature in your 5 minute full heat roast would be 220C°, while the others would range from 200°C to 215°C. Just to give you an idea look at these 2 roasts, where longer roast loses less because the heat is applied differently.



There’s no possible way to lose more if you apply less heat.


It’s not that simple. The loss percentage will depend on how your roast went. Let’s just say that 20% DT with a delta of 10°C won’t be the same as 20% DT with delta sitting at 6°C. And let me be clear here, you can only look at your delta temps once the roast is done, so you know if you went in too fast or too slow for the next one. The delta itself is just an indicator of what you’ve done during the roast, so you can only affect it during, and not at the end of the roast. In short, the loss percentage doesn’t really mean anything. You can’t extrapolate anything for your future roasts from it. Focus on colour as it’s the only true indicator of how the roast went. You say that they look like light roasts, but have you measured them with a colour metre? Because of time and many measurements I’ve taken during the years, I can pretty much tell, within 5 points on a gourmet agtron scale, what the result will be. You can’t pass the SCA exams without that, as you are asked to come within a given result with your roast. I have my doubts that this is possible without a lot of practice. I know those things are expensive, but if you have time, which is money, you can build one yourself. Here’s a link to that thread.

Hope that helps.

% Loss has been used to estimate the degree of roast. Here’s an old Sivitz chart showing the correlation and Artisan software has coded % loss to correlate to roast degree as well in their software.

Now that roast color meters are more available and affordable, I see this changing.

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I tried searching for reference that SCA do consider %loss a way to measure roast degree but I could not find, although it is defiantly there.

Think of two pots full of water A,B. Pot A above a stove turn on to full flame for 2 minutes, pot B above stove turned 20% flame for 2 hours. what would happen? it is a time+heat chemical reaction.

Also why would DT be determined only after the roast? you can practically control it at the end of the roast by keeping your bean temp flat for as long as you want!

I tend to agree which. I had been using a method of % loss to get relatively consistent results and useful parameters for increasing consistency for the same beans. It was just a curiousity that struck me after I rant into consistency/irregularity issues after the aformentioned deep clean. Thanks for your reply.

I was using a color/%loss chart from Sweet Maria’s as my referent not SCA guidelines. I’m a tenured homeroaster not a professional roaster with certifications from SCA and/or Roaster’s Guild.

Some of these baked roasts were pushing that 3min dev time so I am in agreement with you there.

I understand the process, the chemistry (in theory not entirely), and the adjustments with heat, time, air, etc. The reasons I’ve stayed away from color as an indicator to assist in helping me consistent roast profiles and cup results are: (1) color meters are expensive considering my hobbyist situation (2) I tend to roast dry process coffees (Ethiopians in particular) and so variation in bean color isn’t as uniform as most washed coffees (3) color analyzers are freaking expensive!

An additional question I have would be why would a very reputable supplier such as SM’s offer color/% loss charts for assisting in determining roast degree if it was so off base?

@yakster thanks for sharing this Sivitz chart! I’ll look into your Arduino post – thanks!

Well, I can only help so much, but I’ll try one last time, since you haven’t stopped to wonder how I would know what it takes to pass SCA exams and how they determine roast degree. Nor have you stopped to look at the roast profiles to see how your “theory” doesn’t hold water, as your pots. And I will tell you that I avoid thinking, because I know. So, instead of pots with water, try something a bit closer to the roasting process. Stick a potato in the oven at 300°C and at 150°C. Please do this with a fire extinguisher handy. There’s nothing wrong in not knowing. I have made mistakes, and when someone on this forum told me that what I wrote was not correct, I just accepted and told everyone to disregard the post. Feel free to do what you want.

As for DT, because you have not read what I wrote, it is not determined at the end of the roast. To reiterate, it is determined by your actions during the roast and it can help you understand if you went in too fast or too slow. If you try to correct that when you’re into development phase, you’ll only get bad roasts. I’m sorry, but this is the best I can do as far as explaining goes, so I can’t see myself replying again.


I can only tell you that Sivetz and us are not using the same machine. They sell a fluid bed roaster. 221°C is “tan”? 238°C “dark”? It would seem to me that you would be playing with fire, literally, if you tried to bring the beans to those temperatures inside the Bullet. I only went a bit far on seasoning roasts, but I don’t recall the exact temps, since I haven’t connected the roaster for those. Anyway, judging from the temps, it is highly unlikely I’d trust a percentage estimate from 1991 to determine the roast degree. Also, I think they’re talking about commodity coffee.

@thewildcup Well, they offer it as info. The roast degree is determined by measuring colour. They’re just saying how much weight they’ve lost. You can’t know how much you’re losing while roasting, but you can see the colour. As for Ethiopian naturals, you might want to take a look at this photo.

Yeah, some beans might seem inconsistent to the naked eye, but the colour metre will give you the right results and won’t get confused by it. You’ve spent almost 4k on a roaster, but the 700 for a tonino seem too much and you won’t build your own? OK, your choice. Feel free to disregard everything I wrote.

I hear you. Although I’ve seen that post before thanks for sharing it again. One trouble I have with many/most of the recipes shared are right around the 500g charge weight. My charge weight is always 775g. It’s what I formulated my recipes around and that’s the data I’m working from. I tend to get to P5/F5 by the end of the roast otherwise my ROR drops to like 1-2*. I would love to compare recipes at higher charge weights but so far haven’t come across them in any Bullet forums here or elsewhere.

Also, I’m not disregarding what you’re saying. Yes, I bought a $4k roaster back when I had the money, $700 now would be pretty tight for me to casually dropping it on a color meter isn’t as clear cut as you make it seem. I will look into the DIY route or the Tonino but for now I’m just trying to learn about what metrics to adjust and track to produce consistent and solid cups of coffee.

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bow bowing GIF

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Trust me, I would not be saying this to you if I didn’t think it was important. To me, the colour metre is the most important thing that I have. I’d dare say that I think that I’d have better results on a cheaper roaster with a colour metre, than on an expensive one without. I do understand the problem with the money and I did not want to seem arrogant. I apologise as I do realise I came across that way. Unfortunately, the only way to have a Roast vision (Espresso Vision) is to build one yourself. Maybe someone is selling a used one somewhere. You never know if someone upgraded and doesn’t need it anymore. The company no longer exists, but DIY is cheaper than what they were selling it for. The tough part is the calibration, as you can read in billc posts in that thread. You can see that it is a reliable little thing in this Rob Hoos post.

A tale of two color meters… — Hoos Coffee Consulting

Once again, I apologise if I came on too strong about the money. I would take it back if I could.

No worries, I’ll check out the Tonino and DIY options for analyzing color.

I suppose one last question to throw into this thread is how does analyzed color post-roast influence adaptations made to the roast. For example: if the ROR curve is within acceptable parameters for the specific roast but the roast ends too light/dark based on analysis where does one start when it comes to making any changes?

As I have done many times on this forum, I’ll leave a link to Münchow’s course that is free for Bullet users. There you will also find the study about how colour influences flavour, learn about adjustments and the futility of the ROR.

There is a link to a thread that has all of the information for building a color analyzer for about $140.00 US