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Roast Color Nerdy Stuff
renatoa
Top  #41 Print Post
Posted on 02/20/2023 1:51 AM
Is the color really relevant? ... not enough to read the darkness only ?
How many hues could have a "coffee brown" to change the judgment, compared to a monochrome image ?
In colorimetry, brown is an mix of red and green. The coffee brown seems to be an equal balance of the both, I am unable to see any red or green hue in a coffee bean roasted of any degree. Many decades photographer eye...

The guy from Roast Vision sell for 300 his device made using a $5 pulse oximetry sensor, able to distinguish only 36 levels of gray... not even fifty Grin
And SCA quote him as innovative... Shock
Edited by renatoa on 02/20/2023 6:29 AM
 
HarryDog
Top  #42 Print Post
Posted on 02/20/2023 6:16 AM

Quote

renatoa wrote:

If would be mine, according to graph, this would be medium roast.


The Color chart I have, I have no idea how accurate it is but putting the beans on the card they are Full City to Dark.
The Chew taste test dark!

Now the artisan log shows my temps and I think they are low, using my guess at temps Medium?

Using the meter? Because they are positive numbers.

L= lightness
a= (red-green) or redness
b= (yellow-blue) or yellowness

So using the meter reads of the chart I have, the only one I have.

L- 27.38 (How light or dark) puts it at Full City
a=5.82 (How Red) puts it between Full City and Full City+
b=7.62 (How Yellow) puts it between Full City and Full City+

How relevant is the color? I don't know but visually using the chart I put the beans in between Full City and Full city + and I think the meter reading backs that up. Based on eating a bean (Blindfolded) I would say it was a Dark roast.

I'm sure some beans will present darker or lighter then others and the Sumatra is a darker earthier tasting bean?

Do you think I went wrong with comparing the bean to my created color chart?
 
ACEMBL
Top  #43 Print Post
Posted on 02/20/2023 6:18 AM
I’ve been keeping an eye on progress with this thread. Very interesting indeed. Within the visible spectrum Renatoa is spot on with the red green thing, it’s often used in agriculture for detecting ripeness of fruit and veg although not so good for brown.

From a little research it seems the best data might be found in the NIR range so I’ve ordered some bits to make a cheap colour spectrometer. There’s a chap on YouTube with instructions and code on GITHUB.

There are also some nice cheap, visible and NIR spectrum sensors on Sparkfun - plenty to ‘waste time’ on.
 
renatoa
Top  #44 Print Post
Posted on 02/20/2023 6:34 AM

Quote

HarryDog wrote:

Do you think I went wrong with comparing the bean to my created color chart?


No idea, especially on the chew test...
For my roast I am using mainly the weight loss to judge their roast level, regardless of any color and taste.
But weight loss judgment is valid only if related to greens humidity, else...
If you want an evaluation during roast, then color seems the way to go. For me is development time.
 
HarryDog
Top  #45 Print Post
Posted on 02/20/2023 7:11 AM
With my current roaster it's not so easy to check the beans during the roast so just checking after as one more data point.

Weight loss is 16.98%, so the sweet maria chart puts this at Burnt?
Other sites put this at high end of Medium.

What are some trusted numbers for roast levels based on temp and or weight loss? A site I should consider correct values to use as guidelines?
 
renatoa
Top  #46 Print Post
Posted on 02/20/2023 7:32 AM
17% loss is definitely FULL ! Shock You are good at chewing beans Grin
My roasts are mostly around 14%

Trusted number depends on your green moisture, is it in the 10-11% ballpark, at best ? Or 8-12%, at the worst...
My actual greens is 9.8%, measured in the shop at the moment of buy.
Depending on the storage conditions, you can experience severe loss, even 1% per week during summer and open bag.
 
HarryDog
Top  #47 Print Post
Posted on 02/20/2023 7:37 AM

Quote

ACEMBL wrote:

Within the visible spectrum Renatoa is spot on with the red green thing.


That's only part of it but yes. Info from the wiki.

The CIELAB space is three-dimensional and covers the entire gamut (range) of human color perception.
L* is the lightness value
a* axis is relative to the green–red opponent colors
b* axis represents the blue–yellow opponents

This link is a color representation of my result on this roast.
https://www.googl...=%234e3d35
 
renatoa
Top  #48 Print Post
Posted on 02/20/2023 8:00 AM
For those non familiar with the figures above...
CMYK is the color mode intended for printing with ink, i.e. reflected light, i.e. subtractive color model.
RGB is the color mode intended for screen displays, i.e generated light, i.e. additive color model.

CMYK should be used when evaluating real beans color (in the trier for ex.), under a neutral white light.
RGB should be used when looking on a display, a picture of those beans, taken under ideal conditions of exposure and white balance.
 
ACEMBL
Top  #49 Print Post
Posted on 02/20/2023 9:14 AM

Quote

HarryDog wrote:

Quote

ACEMBL wrote:

Within the visible spectrum Renatoa is spot on with the red green thing.


That's only part of it but yes. Info from the wiki.

The CIELAB space is three-dimensional and covers the entire gamut (range) of human color perception.
L* is the lightness value
a* axis is relative to the green–red opponent colors
b* axis represents the blue–yellow opponents

This link is a color representation of my result on this roast.
https://www.googl...=%234e3d35


Oh I agree CIElab is a good way of describing what’s seen. I was mainly pointing out the fact that the main change is observed in the red green axis. However, from what I’ve read (allowing for some companies not sharing their IP) most sampling equipment uses selective NIR wavelengths for the ‘agtron type’ scales as theres greater quantifiable difference across the roast range.
 
HarryDog
Top  #50 Print Post
Posted on 02/20/2023 9:36 AM
Yes from what I have read 880nm wavelength is used on some Agtron type units (Much more separation), I think I seen this on a spec sheet for an Agtron model as well. If I see that again will post the info, I just can't say for sure.

I was scanning that info to see what color space would be best to use on this cheap meter. So far samples of Hunterlab and CIElab were close. I just thought CIElab would be better at sampling more yellows? Then Hunterlab that expands in the blue area, but claims to be more uniform. Probably just a toss up.

Renatoa posted that paper from HunterLabs comparing 640nm to 880nm.
Edited by HarryDog on 02/20/2023 9:43 AM
 
oldgrumpus
Top  #51 Print Post
Posted on 02/21/2023 6:03 PM
In keeping with the title of this thread, here's some very nerdy stuff. It's a study that delves into time spent in the development phase and color or degree-of-roast, and how both influence the results in the cup.

https://www.mdpi....710/6/4/70
 
MaKoMo
Top  #52 Print Post
Posted on 03/05/2023 9:37 AM
More nerdy stuff on roast color: Understanding Roast Color
 
CK
Top  #53 Print Post
Posted on 03/06/2023 3:39 PM
What a great, detailed, and professional presentation of the topic. A shout of thanks to Artisan for publishing these findings and research.
 
oldgrumpus
Top  #54 Print Post
Posted on 03/08/2023 5:59 PM
I also read the article posted here by MaKoMo. Lot's of info and very nerdy indeed. Grin I recommend it highly for those who enjoy the deep-dive.

It's interesting to me that so much effort is put into accuracy and precision of reading color, which I understand, especially for high production commercial roasters to get something close to repeatability, but we are dealing with an agricultural product that on many levels, varies widely, not only in a single-year's harvest, but also geographically, by genetics and so on...

It would be interesting to see how much variation in the degree of color measured by a professional-level color reading device is actually detectable in cupping tests.
 
Piotrkurak
Top  #55 Print Post
Posted on 03/17/2023 10:46 AM
Just to stick in my $0.02: which bean do you select? I have probably several different levels of color in my last batch, not including the kind of green beans when I forgot to hit the start button on the new to me Behmore as it beeped for attention at the 70% roast point.
 
oldgrumpus
Top  #56 Print Post
Posted on 03/17/2023 9:36 PM
Typically, roast color evaluation is measured using a typical random sample comprised of enough beans for the sample, then ground and leveled before measuring. The odd bean in the sample should be measured with the rest if the others are left in and not removed.
 
ACEMBL
Top  #57 Print Post
Posted on 03/23/2023 9:31 AM
OK, so a single spot sample will throw up all sorts of issues. Indeed, different lighting, variances in bean, any refraction … will all add to differing results. So multiple sampling controlled lighting and data regression seem to be necessary.

I’m having a little play to see whether I can identify the matching average colour to trigger an event (different method but similar result to ColourTrak). There are a couple of different methods I’m exploring so we’ll see whether either is suitable! My poor little Raspberry Pi is going to be busy! Just a shame my coding ability is almost non-existent.

Great little thread!
 
Piotrkurak
Top  #58 Print Post
Posted on 03/23/2023 10:41 AM
I now can see why bean temp is a criteria, that is something you can measure on the fly without so many variables.

Since the maillard reaction is a function of sugar/starch carmalization might co relating sugar content in the raw bean to roast color be more appropriate? Not sure how to determine starch quantity
Edited by Piotrkurak on 03/23/2023 10:50 AM
 
randytsuch
Top  #59 Print Post
Posted on 03/27/2023 2:37 PM
Thread on HB about a diy color meter.

https://www.home-...86508.html

github info seems to be a work in progress, but looks like it has potential to me.

To bad I don't have a 3d printer or I'd try it now.

Randy
 
ACEMBL
Top  #60 Print Post
Posted on 03/28/2023 3:57 PM
If you don’t have a printer there are lots of project boxes out there. I’m doing something similar and am using a small electrical junction box. A bit of plastic putty, A sharp craft knife and you should be good to go!
 
oldgrumpus
Top  #61 Print Post
Posted on 03/28/2023 11:14 PM
Also, depending on where you are, there may be very inexpensive places to have the printing done. Where I live, Craigslist, Shapeways, 3dhubs, and others....
 
renatoa
Top  #62 Print Post
Posted on 03/29/2023 1:52 AM
Still I am confused about the usefulness of such methods... if they aren't able to tell you degree of roast during development, and tell you with enough precision: Drop ! 3, 2, 1 ... NOW !

Assuming the grounds measurement is reproducible enough... discussions on HB shows they aren't... will ask those following here, generically, not only the thread author Grin :
How reproducible are our roasts ?
If we decide a roast give us the right Agtron, are we able to reproduce it within the same limits as the Agtron measurement ?
 
Piotrkurak
Top  #63 Print Post
Posted on 03/29/2023 10:18 AM

Quote

renatoa wrote:

Still I am confused about the usefulness of such methods... if they aren't able to tell you degree of roast during development, and tell you with enough precision: Drop ! 3, 2, 1.......
How reproducible are our roasts ?
If we decide a roast give us the right Agtron, are we able to reproduce it within the same limits as the Agtron measurement ?


I agree:too many variables to control for with too many solutions. Not easily feasible from an instrumentation techs point of view.even with computer control
 
oldgrumpus
Top  #64 Print Post
Posted on 03/29/2023 11:19 PM
I think the confusion comes from the fact we sometime try to combine two different methods (philosophies). One uses degree of time in development phase. This method does not account for roast color. The other does not account for time in development, but prioritizes the color of the roast instead.

What I have just said above is most definitely an oversimplification, which I am using to clear up the confusion. Getting into it deeper, you may want to look at this video. It has answered a lot of questions for me, and since using this recent change in roast philosophy, I've been getting better results. I'm speaking for myself. Others have their preferences. No right or wrong here....

I would agree with the notion that 80 percent of our priority should be color and 20 percent pre-first-crack temp inputs. Time in development is important too, but one can achieve the same color in development even though one can spend more or less time there depending on the rate of rise. Staying there longer will give the dreaded "baked" flavor, and speeding up too much will give more acidity and fruitiness, but going too quickly will end up with it's own issues. Minimum time after first crack 1:20, and mid point between first-crack and second-crack, about 3 minutes... which is where I'm dropping with excellent results. For those going for fruity, 1:20 is better. Main target is first crack at 9 minutes.

Too much to say here. Probably already lost some of you reading this... sorry.

https://www.youtu...U&t=6s
Edited by oldgrumpus on 03/29/2023 11:32 PM
 
allenb
Top  #65 Print Post
Posted on 03/30/2023 8:32 AM

Quote

I think the confusion comes from the fact we sometime try to combine two different methods (philosophies). One uses degree of time in development phase. This method does not account for roast color. The other does not account for time in development, but prioritizes the color of the roast instead.


Interesting point you've made. In watching experienced roasters on mid sized shop drum roasters over the years, I was able to see what they used for sensory input to control this final stage of the roast. They knew from lots of experience about where to set the gas valve when getting near 1C. Most of them would have a sample tray of roasted beans and a good light for color reference and as soon as the first audible snaps of 1C started, they would start pulling the trier every few seconds. I think they were able to sense the rate of the cracking of 1C and could tell by how fast or slow the color was changing and by these two sensory inputs, knew when to end the roast for a given roast level.
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
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