HomeRoast Digest


Topic: Agtron tiles or chart (27 msgs / 830 lines)
1) From: Treshell
I would love to know of any tiles that were affordable in price.  Or a
really good chart.  Any idea?
Treshell Jones

2) From: Brett Mason
Tom Says...
So why don't I talk about degree of roast in terms of color? Isn't that what
the Agtron number system that pros use all about? Yes it is, but it requires
either an Agtron photospectrometer to automatically read the color of the
roaster, ground coffee. Or you need the $200 SCAA-Agtron Roast Color Tile
Kit. I have this kit, and I also have experience in digital color correction
...so let me tell you that there's a lot more involved with "eyeballing" the
color of the coffee and the color of the disks. You need balanced white
light, no glare, and the ability to offset for textures and light
absorption. What I am saying is ...it's so difficult to accurately judge
that is barely worth the effort. Ken Davids provides 4 color tiles in the
back of Home Coffee Roasting that help establish some basis of reference,
and I think that's about as far as color analysis by the naked eye should go
in terms of coffee roasting!http://www.sweetmarias.com/tiny_joy_html/sepoct02.htmlSo - well they may help you...  But maybe you'll also need an oil
measurement device, a moisture measurement device, and the ability to
guarantee the roast is consistent through the bean....  There's lots more to
roasting than the color of the skin of the bean...
Keep asking questions, and keep trying to roast...
Good roasting is a result of experience.
Experience is a result of bad roasting.
Brett
On Dec 8, 2007 10:12 PM, Treshell  wrote:
<Snip>
unsvbscribes) go tohttp://sweetmarias.com/maillistinfo.html#personalsettings<Snip>
-- 
Cheers,
Bretthttp://homeroast.freeservers.com

3) From: raymanowen
I suspect Agtron is a farce. Can one judge a bean by its surface color, any
more so than humans?
The interior of a bean is the overwhelming location of the majority of
coffee flavor and aroma. With any ramping of the temperature, the roast
level of the bean's interior will lag the surface, so what you see is mostly
not what you get.
I realize the Crack sounds are not surface events, any more than the
interior temperature is the same as the surface temperature.
The visible appearance is strictly Skin Color, and might be misleading. Red
traffic signals can be misleading too. If you approach a red light at
5,000,000 mph, the Doppler shift would shorten the wavelength to a pretty
shade of Green.
That's a blue shift, compared to the red shift of the most distant galaxie
in the expanding universe.
Cheers, Mabuhay -RayO, aka Opa!
Keep looking up! - -Jack Horkheimer, Miami Museum of Science and Space
Transit Planetarium
On Dec 8, 2007 9:12 PM, Treshell  wrote:
<Snip>

4) From: Joseph Robertson
Ray,
I suspect you suspect wrong. I say this because I'm not totally sure you
know that this has nothing to do with the surface color of the bean. Brett,
I believe has hit the nail on the head.
If you notice his post above he mentions ground coffee. The Agtron reads the
reflection from the mix or ground coffee. Now weather or not this
information is of any use for us home roasters is up for question. If you
don't mind the fee involved you can send a sample of your roasted beans to a
lab likehttp://www.coffeelab.com/Pretty steep fee though. Being a coffee geek I think it would be fun to own
an Agtron but as Brett points out that is just one of the costs of a serious
coffee lab. I am scheduled for the roasting course they offer so maybe I
will be able to speak with a full deck of beans when I get done with this
entry level program. Well hopefully a fuller deck anyway.
JoeR
On Dec 8, 2007 8:58 PM,  wrote:
<Snip>

5) From: Vicki Smith
When I first began home roasting using something like the tiles seemed 
very important to me. I even explored the confusing world of paint 
chips. Now though, even though it's only been a couple of years, I see 
them as not so important for someone like me.
I take notes during my roasts with the goal of being able to improve on 
(or if I hit one, duplicate) what I have done. As evaluating the 
finished colour using an Agtron tiles is a post roast measurement, it 
isn't really much use to me. In fact, the only thing I evaluate after 
the roast is done is the taste and how rest changes that.
If I have a good record of the roast profile that led to my great (or 
not so great) coffee, then the colour match of the Agtron tile doesn't 
give me much in the way of additional useful information.
I'd probably feel differently if I were roasting commercially and tuning 
in my roaster for a particular bean/blend.
Just one more take on the subject...
vicki

6) From: Rodney Winchell
Found this set for $20, haven't purchased.http://baristabest.com/color_tile_set.htmrod

7) From: Brett Mason
Let's ask the whole question here, and see if we can't get you some help....
Has anyone used Agtron color tiles (or similar) to help in your roasting, or
learning of roasting?
What did you specifically use?
How did these help you the most?
What do you feel could have added to your learning?
Having used these, what would you recommend?
Cheers,
Brett
On Dec 9, 2007 3:16 PM, Rodney Winchell  wrote:
<Snip>
-- 
Cheers,
Bretthttp://homeroast.freeservers.com

8) From: Rich
Being somewhat tight, I printed out the SM full sized photos that go 
with the descriptions.  I used high gloss photo paper.  seems to do the 
job and is no longer used either.
Brett Mason wrote:
<Snip>

9) From: Homeroaster
I have no use for color tiles.  If I needed complete uniformity from batch 
to batch, for a particular commercial account, or I roasted huge amounts of 
beans for sale, I could see the need for having a comparison color to match 
it to, from batch to batch.  For what I do, roasting to smell, time and 
temperature works better.
*********************
Ed Needham
"to absurdity and beyond!"http://www.homeroaster.com*********************

10) From: Scott Miller
Agreed.
Agtron sounds like a neat idea, but it is still after the fact information.
If you have good time/temp logs, it's possible to do adjustments to a
profile from that information.
cheers,
Scott
On Dec 9, 2007 6:56 PM, Homeroaster  wrote:
<Snip>

11) From: Treshell
<Snip>
Tried to order them a couple of months ago.  If you follow the order section
you find that August 12, 2005 they would be up in a week.  However still not
up.
treshell

12) From: Treshell
<Snip>
this format, some or all of this message may not be legible.
<Snip>
...
<Snip>
 or
<Snip>
Your right, I want them with out paying a lot because my friends the Monks
go by the agtron scale in their roast.  I take them some of Tomıs fancy
coffee and we roast and share them.  Gives the monks coffee they wouldnıt
have and gives me the use of their fancy roaster.  The first time I said I
wanted a city roast I just got an odd stare from father.  I just want them
as education tools.  I have found a chart that sort of helps but who is to
say my monitor is near correct.
treshell

13) From: raymanowen
"If you notice his post above he mentions ground coffee."
How utterly ridiculous is a roast measurement system that is non-functional
until the roast has been stopped, the beans cooled and ground.
Maybe I won't shell out $200 for a Standard Roast guide that doesn't do any
guiding until the roast is all done and in the can. An exposure meter that
gives shutter speed and lens iris information after the film is processed
and proofed, is only useful for glacier or evolution documentation.
A MacBeth or Cosar color densitometer may be had on eBay. They have their
own light source, are cheaper, more precise and objective, and the Cyan
density could be recalibrated to Near I-R for an in-depth look at the
roasting progress.
To quote W.C. Fields, anyone with a little perspicacity could make a killing
with the coffee roast evaluation gadgets and put Agtron back under a rock.
Cheers, Mabuhay -rayO, aka Opa!
That's fine, Watson- How does it taste?
On Dec 9, 2007 12:58 AM, Joseph Robertson  wrote:
<Snip>

14) From: Lynne
Ooooh - what monks? Please share - sounds so interesting!
Lynne
treshell wrote:
<Snip>
Your right, I want them with out paying a lot because my friends the Monks
<Snip>

15) From: Bill Hill
I have heard from my friend Fr. Glen Szczehowski (the new priest in
Powell) that the monks have a sweet sweet roaster, all computerized
and such.  If you have some time, could you tell me about it?  That's
awesome that they let you use their roaster in exchange for different
beans.  Totally sweet.
Peace
Bill
On 12/9/07, Lynne  wrote:
<Snip>

16) From: Homeroaster
I would rather roast for flavor than color.  There is no hard, fast 
correlation between the two.  A bean roasted fast to a certain color and a 
bean roasted slow to the same color will be totally different.
Agtron is for large commercial concerns.  Staub has linked it with laser 
color sensors that can read the color of preroasted individual beans and 
roasted beans to cull out the variants.  One machine I saw spits beans out 
like a machine gun, but reads every single one for proper color.
For a homeroaster to use Agtron color charts, they would have to sample a 
single roast at specified intervals near the end of the roast, then grind 
and cup the beans, and determine what the color of the beans were that made 
the best cup.  The color tile would be part of the quality control process, 
along with roaster temperatures, and timing of the roast.
Of course Agtron tiles could also be useful for comparing roast colors in 
conversation about coffee, so possibly two homeroasters in different parts 
of the world could compare colors with a degree of objectivity.  That would 
not assure that flavors would be the same though.
*********************
Ed Needham
"to absurdity and beyond!"http://www.homeroaster.com*********************

17) From: David Schooley
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I did some experiments a year or so ago where I was taking pictures of  
roasts to incorporate into my logs. The pictures were of a few whole  
beans and a small mound of grinds. The idea was to compare colors when  
doing multiple roasts of the same bean. I gave up after 4 or 5 tries.  
As Tom mentions on the SM website, the white balance and lighting have  
to be consistent, and making that happen was way too much work when  
taking pictures with a digicam and tripod while the beans were sitting  
on my dining room table. Even if the white balance is set using a grey  
card, the lighting in the room can still throw things off. I was using  
my iRoast at the time, so I was spending 15 minutes roasting the  
coffee and another 20 taking pictures.
As for why I even bothered, I was playing with iRoast profiles at the  
time. If I roast a bean twice to the same degree of roast as measured  
by the color but with different profiles, then any taste differences  
should be due to differences in the profiles. If I roast a bean twice  
with the same profile and get different tastes, then a comparison of  
colors might explain difference, i.e., the degree of roast was  
different. Does the color of a single roast tell me anything, perhaps  
not, but when compared to other roasts, it does. To expand on the  
photography analogy below: the mythical post-processing exposure meter  
applied to a single picture might not tell you anything useful, but if  
you apply it to a whole bunch of similar pictures, it might tell you  
why the good ones were good and the bad ones were bad and if the  
differences were due to exposure or processing.
For most of us, variations between roasts are not a big deal. They can  
even be interesting. If I was a commercial roaster and my reputation  
and livelihood depended on my ability to deliver consistent beans day  
in and day out to demanding customers, then some sort of color  
matching would be part of my quality assurance process.
On Dec 9, 2007, at 9:09 PM, raymanowen wrote:
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I did some experiments a =
year or so ago where I was taking pictures of roasts to incorporate into =
my logs. The pictures were of a few whole beans and a small mound of =
grinds. The idea was to compare colors when doing multiple roasts of the =
same bean. I gave up after 4 or 5 tries. As Tom mentions on the SM =
website, the white balance and lighting have to be consistent, and =
making that happen was way too much work when taking pictures with a =
digicam and tripod while the beans were sitting on my dining room table. =
Even if the white balance is set using a grey card, the lighting in the =
room can still throw things off. I was using my iRoast at the time, so I =
was spending 15 minutes roasting the coffee and another 20 taking =
pictures. 
As for why I even = bothered, I was playing with iRoast profiles at the time. If I roast a = bean twice to the same degree of roast as measured by the color but with = different profiles, then any taste differences should be due to = differences in the profiles. If I roast a bean twice with the same = profile and get different tastes, then a comparison of colors might = explain difference, i.e., the degree of roast was different. Does the = color of a single roast tell me anything, perhaps not, but when compared = to other roasts, it does. To expand on the photography analogy below: = the mythical post-processing exposure meter applied to a single picture = might not tell you anything useful, but if you apply it to a whole bunch = of similar pictures, it might tell you why the good ones were good and = the bad ones were bad and if the differences were due to exposure or = processing.
For most of us, variations = between roasts are not a big deal. They can even be interesting. If I = was a commercial roaster and my reputation and livelihood depended on my = ability to deliver consistent beans day in and day out to demanding = customers, then some sort of color matching would be part of my quality = assurance process.
On Dec 9, 2007, = at 9:09 PM, raymanowen = wrote:
"If you notice his post above he mentions ground = coffee." How utterly ridiculous is a roast measurement system = that is non-functional until the roast has been stopped, the beans = cooled and ground. Maybe I won't shell out $200 for a Standard = Roast guide that doesn't do any guiding until the roast is all done and = in the can. An exposure meter that gives shutter speed and lens iris = information after the film is processed and proofed, is only useful for = glacier or evolution documentation. A MacBeth or Cosar color = densitometer may be had on eBay. They have their own light source, are = cheaper, more precise and objective, and the Cyan density could be = recalibrated to Near I-R for an in-depth look at the roasting progress. = To quote W.C. Fields, anyone with a little perspicacity could = make a killing with the coffee roast evaluation gadgets and put Agtron = back under a rock. Cheers, Mabuhay -rayO, aka Opa! That's = fine, Watson- How does it taste? On Dec 9, 2007 12:58 AM, Joseph Robertson <theotherjo > wrote: Ray, I suspect = you suspect wrong. I say this because I'm not totally sure you know that = this has nothing to do with the surface color of the bean. Brett, I = believe has hit the nail on the head. If you notice his post above = he mentions ground coffee. The Agtron reads the reflection from the mix = or ground coffee. Now weather or not this information is of any use for = us home roasters is up for question. If you don't mind the fee involved = you can send a sample of your roasted beans to a lab like http://www.coffeelab.com/Pretty steep fee = though. Being a coffee geek I think it would be fun to own an Agtron but = as Brett points out that is just one of the costs of a serious coffee = lab. I am scheduled for the roasting course they offer so maybe I will = be able to speak with a full deck of beans when I get done with this = entry level program. Well hopefully a fuller deck anyway. = JoeR On Dec = 8, 2007 8:58 PM, <raymanowen> wrote: I suspect Agtron = is a farce. Can one judge a bean by its surface color, any more so than = humans? The interior of a bean is the overwhelming location of = the majority of coffee flavor and aroma. With any ramping of the = temperature, the roast level of the bean's interior will lag the = surface, so what you see is mostly not what you get. I realize = the Crack sounds are not surface events, any more than the interior = temperature is the same as the surface temperature. The visible = appearance is strictly Skin Color, and might be misleading. Red traffic = signals can be misleading too. If you approach a red light at 5,000,000 = mph, the Doppler shift would shorten the wavelength to a pretty shade of = Green. That's a blue shift, compared to the red shift of the = most distant galaxie in the expanding universe. Cheers, Mabuhay = -RayO, aka Opa! Keep looking up! - -Jack Horkheimer, Miami Museum = of Science and Space Transit Planetarium On = Dec 8, 2007 9:12 PM, Treshell <treshell> wrote: I would love to know of any tiles that were = affordable in price.  Or a really good chart.  Any = idea? Treshell = Jones

18) From: Justin Marquez
It is not ridiculous at all if:
A) You have a roaster that can be "adjusted" somehow to reliably produce a
repeatable roast level
AND...
B) You roast a lot of coffee and want to have it all turn out the same.
A commercial roaster will roast some batches to refine what he is getting
and then "fire for effect".  The Agtron tiles help him to refine the roast
level and to quickly check the results after a batch.
They probably don't have much use for us homeroasters, particulary for the
zen-style roasters amongst us where the roast levels vary a bit from batch
to batch.
Safe Journeys and Sweet Music
Justin Marquez (CYPRESS, TX)
On Dec 9, 2007 9:09 PM,  wrote:
<Snip>
--

19) From: miKe mcKoffee
Indeed, quality control is ridiculous (the purpose of the Agtron Process
Analyzer and cheaper Agtron/SCAA Tiles). Oh wait, unless some Roast Masters
actually care about consistency in their roasts batch to batch going out the
door.
 
Kona Kurmudgeon miKe mcKoffee
www.mcKonaKoffee.com
URL to Rosto mods, FrankenFormer, some recipes etc:http://www.mckoffee.com/Ultimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/	From: homeroast-admin
[mailto:homeroast-admin] On Behalf Of
raymanowen
	Sent: Sunday, December 09, 2007 7:10 PM
	
	"If you notice his post above he mentions ground coffee."
	
	How utterly ridiculous is a roast measurement system that is
non-functional until the roast has been stopped, the beans cooled and
ground. 
	
	Maybe I won't shell out $200 for a Standard Roast guide that doesn't
do any guiding until the roast is all done and in the can. An exposure meter
that gives shutter speed and lens iris information after the film is
processed and proofed, is only useful for glacier or evolution
documentation. 
	
	A MacBeth or Cosar color densitometer may be had on eBay. They have
their own light source, are cheaper, more precise and objective, and the
Cyan density could be recalibrated to Near I-R for an in-depth look at the
roasting progress. 
	
	To quote W.C. Fields, anyone with a little perspicacity could make a
killing with the coffee roast evaluation gadgets and put Agtron back under a
rock.
	
	Cheers, Mabuhay -rayO, aka Opa!
	
	That's fine, Watson- How does it taste?

20) From: Joseph Robertson
Thanks Mike,
It is nice to see something can be explained in less than 5 sentences.
Based on the fact that it takes me many more to do the same thing I guess I
will a grasshopper for some time to come.
Cheers,
JoeR
On Dec 11, 2007 8:08 AM, miKe mcKoffee  wrote:
<Snip>

21) From: Homeroaster
Mike,
 Didja get your new roaster yet?  Roasting with it?
As to color of the roast, I'll bet it's more important to you now than it 
was earlier! Your customers are going to want that 'same thing I got last 
week', and they will tell you if it's the slightest bit different.
The whole process of taking multiple samples near the end of a roast and 
comparing it to multiple samples of several other roast profiles gets very 
complicated and involved for someone roasting maybe a half pound at a time 
in a Hottop, Behmor or GenCafe.  I'm not aware of a home roasting device 
that allows easy samples to be taken from one roast.  I can do it, with 
difficulty through the open end of my 5 pound drum, and I have used that 
technique from time to time to 'nail' a roast, but generally, I don't find 
the need to take precision quite that far.  And color of the bean is not one 
of the primary criteria I use for judging a roast.  Color of the chaff in 
the crack of the bean, oil spotting or no oil spotting, end of roast in 
relation to second crack, smoke generation and smell near the end of the 
roast are generally more helpful than comparing my roasted and ground beans 
to a color tile.
Don't get me wrong.  There is a place for Agtron reference tiles, but I 
think their usefulness to a homeroaster is very limited.  BUT!  If having 
and using the tiles helps someone become a more competent roaster, then by 
all means, get them and display/use them proudly!
(I'm on pain meds due to surgery this morning.  I'll spare the details, but 
I've deemed it the Star Trek maneuver--going where no one has gone before 
and blasting/cutting things with a big 'ol laser.  So if this post doesn't 
make as much sense to you as it does to me, just chalk it up to the meds!)
*********************
Ed Needham
"to absurdity and beyond!"http://www.homeroaster.com*********************

22) From: Brian Kamnetz
Best wishes for a speedy recovery, Ed.
Brian
On Dec 11, 2007 1:26 PM, Homeroaster  wrote:
<Snip>

23) From: Verdova
Get well soon ED

24) From: miKe mcKoffee
I agree with you 99.99% Ed. (Don't have a clue what the 0.01% disagreement
is, but just had to disagree a bit:-)
Nope, still waiting of build completion which should within a week or so.
Then shipping and installation. Likely another month 'til install and
operational.
Typed while 2x 332gr loads Aged Sumatra roasting, 2x WP Yirg' batches
already done while eating dinner, 2x MM batches to go tonight. (30% elements
of 12# our main Ohana Blend.) Of course done after 12 1/2hrs at the Kafe
earlier today! Have 20 SO 330+gr CCR HT batches this weekend... (Won't be
going into the Kafe to "work" tomorrow, just to go over food & supplies
inventory for early Monday morning shopping. Oh and pick up this week's
timesheets to do payroll for my 3 employees for Monday. And Sunday 8am be
their to work with the guy I hired doing back end remodeling work in-between
making a bunch of batches or cranberry orange, pineapple mango macadamia
nut, and apricot walnut scones. (Pre-make the scone dough and individually
wrap then freeze for later baking during the week.) Next week will be
working on our custom chai blend. Two new black teas on the way, single
Estate Assam and Darjeeling's plus bulk of the 6 whole spices will be using.
But crap, the end of the month is creeping up with various sundry Federal
and State taxes to do! And we still are not quite decided on the main Kafe
interior paint color, though maybe. Painting the bathroom with the color we
may use...
What? This was Agtron tile discussion? Oops, I ramble. I'm not using them
either actually though may in the future. Or may not! Which does not mean I
dismiss their potential usefulness.
Wow, while busily rambling two HT's just dumped their batches of Aged
Sumatra seconds apart! At least that makes it a wee bit easier to HOME ROAST
small boatloads of coffee weekly with pretty decent automation and
consistency. (As well it should easily pushing $5k, actually a bit more, for
the tandem act:-)
Time to empty the cooling trays, vac 'em out and fire off the Malabar...
Have a Great weekend.
Pacific Northwest Gathering VIhttp://www.mcKonaKoffee.comUltimately the quest for Koffee Nirvana is a solitary path. To know I must">http://home.comcast.net/~mckona/PNWGVI.htmKona Konnaisseur miKe mcKoffeehttp://www.mcKonaKoffee.comUltimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/
<Snip>

25) From: raymanowen
"...linked it with laser color sensors that can read the color of preroasted
individual beans..."
Interesting concept- a device that employs Light Amplification by Stimulated
Electromagnetic Radiation- a source of monochromatic light that can be timed
with knife edge precision, used to "read the color of preroasted individual
beans."
An monochromatic electric light that "can read the color of preroasted
individual beans."
Ronco's ultrasonic transducer that can read the pitch of a cricket's chirp.
Makes a great gift...
The laser color separators do indeed use laser light sources- to expose film
on rotating drums. The colors are read quite separate from the laser, but
next door to it in a dark chamber from which the original artwork is
illuminated on a congruent drum by a white light source.
The individual colors filtered by gel filters and photomultipliers trigger
the lasers to produce the halftone color dots.
The technology of ceramic bathroom tiles of the 20's thru 40's has morphed
to keep abreast of 60's technology. Or the story has...
Cheers, Mabuhay -RayO, aka Opa!
On Dec 9, 2007 11:02 PM, Homeroaster  wrote:
<Snip>
-- 
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976

26) From: Allon Stern
On Dec 15, 2007, at 3:36 AM, raymanowen wrote:
<Snip>
LASERs are not necessarily monochromatic. I have a very nice argon  
laser which will run multimode.
Anyway, doing some patent searching does show that measuring narrow  
portions of spectrum is used in this sort of color matching.
US Patent 6106877:
Method of terminating roasting of bulk materials in real time on  
basis of objectively determined color of materials
which reads, in part:
In such a reflectometer, monochromatic, e.g. laser, light is directed  
towards the beans being roasted and into an observation area (or  
volume) thereof. The remainder of the instrument is configured so  
that the amount of light reflected by the beans and detected by it is  
independent of the relative position of any given bean in the  
observation volume by placing a photo or radiation detector of the  
reflectometer at the infinity focal point of a lens. The lens  
diameter, its focal length, and the effective diameter of the  
radiation detector are selected and arranged so that they define the  
desired observation volume on the side of the lens opposite the  
detector. Laser light reflected off a bean at any place within the  
observation volume will have the same light reflection  
characteristic, e.g. intensity.
Other instruments adapted to accurately determine the color of the  
beans during roasting independent of the relative positions of the  
beans and/or as a result of their motion can of course be substituted  
for the reflectometer described in the preceding paragraph. However,  
the latter is believed to be particularly suitable and cost effective  
for this purpose.
In a preferred embodiment of the invention, a continuous or  
intermittent flow of coffee beans of the batch being roasted is  
directed past a convenient location, say proximate a window which  
permits viewing of the roasting machine interior from the exterior  
thereof. The reflectometer is positioned exteriorly of that window so  
that the observation volume of the reflectometer intercepts the flow  
of beans.
It is presently preferred to choose a light source for the  
reflectometer which emits light of a wavelength at which the light  
reflected off the beans exhibits maximum activity. For example, most  
coffee beans are roasted to a color which lies in a range between  
approximately 720-760 nm. For such an application a light source is  
selected which has a wavelength at which maximum rates of change  
occur in the light reflected by the beans. For coffee bean roasting,  
an infrared laser lasing at a wavelength of about 790 nm has shown  
optimal results.
As the color of the coffee beans approaches the desired color of,  
say, 730 nm, increasing amounts of the infrared laser light are  
absorbed, decreasing the intensity of the light reflected by the  
beans correspondingly. Such a marked drop in the intensity of the  
reflected light is relatively easily and accurately detectable and  
facilitates the determination when roasting should end. When this  
point has been reached, the reflectometer generates a signal which is  
used to instantly terminate roasting.
Changes in light reflections not associated with bean colors can be  
caused by oil films which typically form on the surface of the beans,  
especially coffee beans, during roasting. To neutralize such  
reflections, a linearly polarized light source such as a diode laser  
is used in the reflectometer, and a cross polarizer is placed between  
the lens and the radiation detector. As a result, the reflectometer  
is sensitive to only the linearly polarized light reflected off the  
beans.
-
allon

27) From: Allon Stern
On Dec 15, 2007, at 12:03 PM, Allon Stern wrote:
<Snip>
correction: in this sort of application.
I had originally found a couple of color matching patents which used  
lasers, but then I found the roasting patent, so I changed my email  
that I was composing, but didn't change the statement above....this  
patent shows lasers being used for determining when a desired color  
is reached, but is not useful for matching arbitrary colors.
-
allon


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