Density and Roasting - Page 2

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
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keno
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#11: Post by keno »

Dave,

Not sure about the video, but I remember reading this article that Joe wrote about density:

https://joemarrocco.com/2016/10/24/coff ... t-matters/

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Boldjava (original poster)
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#12: Post by Boldjava (original poster) »

This is not the piece I was looking for but is a cute one from Joe when he was still working for Mill City:

http://www.youtube.com/watch?v=rilpdy7o7Tw
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GC7
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#13: Post by GC7 »

Boldjava wrote:This is not the piece I was looking for but is a cut one from Joe when he was still working for Mill City:

http://www.youtube.com/watch?v=rilpdy7o7Tw
That was a cool demonstration that illustrates the point somewhat. I'm not sure water may be more insulation then density but it did make the point.

I have a question or theory for roasters with small capacity and perhaps a bit underpowered roasters. I consider my HotTop in that category. What if you took the 227 gram (1/2 pound charge) and put it in a jar in a microwave for 30 seconds to heat up and "activate" the moisture in the interior before charging into the hot drum. I have done this as an experiment and it obviously changes the turn temperature and the dry time. I've actually seen good results with softer naturals where I want to charge lower but not drag on the roasts too long.

Is this relevant?

Rickpatbrown
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#14: Post by Rickpatbrown »

Boldjava wrote:Absolutely, but let's not the achievable suffer for the perfect. We are home roasters, seeking to add to the knowledge bin, or that's how I look at it.
Ok. So channeling Mr. Wizard, I was curious as to how far off I actually was.

In method 1, I used a $4,000 scale which reads 0.0001g
Method 2, I used a $10 scale that reads 0.1g, but the last digit is uncertain.

I did not calibrate either, but the lab scale has been calibrated in the past few months.

The idea is to fill both containers to a very repeatable point. The narrower the glass at that point, the more reproducible it will be and the greater your accuracy. Google volumetric flasks for an ideal container. Obviously, you'll need to be able to get beans in there.

1st) I filled the container with water to my mark and then weighed it.
2nd) I put in some green beans and the water level rose. I weighed again to get the weight of the beans.
3rd) I removed exactly enough water to return to the mark where I started. Weighing again will give me the weight of the water that I removed.

Water at room temperature is 1g/mL (thank you metric system :wink: ). Accurate scales can measure weight way more accurately than I can measure volume. The best I can do is try to get the bottom of the water meniscus exactly at the mark I choose on my container. Estimating the volume based on scale markers is really tough. Large measurements can rectify this, but I dont want to dunk 250grams of beans in the name of measuring density.

I used about 10g of beans for each measurement, so 30-40g for a triplicate measurement.

Method 1 gave me a densities of
1.2175
1.2034
1.2369
Average is 1.2193g SD of 0.0168

Method 2 gave me densities of
1.20
1.19
1.47
Average is 1.29g SD 0.16* see comment below.

My technique was not perfect. When putting beans in the water, they tend to form air bubbles. Trial 3 in method 2 included shaking and tapping to release the bubbles. In this case, it released 3 trials worth of air bubbles ~0.27mL of space. Also, I did complete replicates for method 1, meaning I dumped out everything, added fresh water, etc. Method 2, I removed water to return to the mark and just added more beans. I'm not sure how this propagates error, or if the water absorbs into the bean over the couple of minutes I took to measure, but if sure was easier. *The SD given above should have been much lower had I removed the air each time. In the end, I think I scienced the s$%@t out of this enough and could just go on with my life.

What's the take home message? Idk. What are the differences in density that would lead you to roast differently? What is the difference in density as a bean dries out of a year of home storage?

I kind of liked how easy the home method was, though.

Method 1


Method 2


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Boldjava (original poster)
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#15: Post by Boldjava (original poster) »

Rickpatbrown wrote:What's the take home message? Idk. What are the differences in density that would lead you to roast differently?
...

You have no idea how much fun I had reading thru you post.

Others with gas burners, fans, PIDs, charts, etc., have more tools with which to approach density and how it impacts a particular roast. In my case, my take home is a very loose spit ball knowledge of "how well can this bean handle heat compared to the other beans I roast?" I don't even have the tools to ramp as many of you guys do (I roast on a Gene now). But it is great to learn, even on a modest level, that which I can and apply it and put the best shine I can to the bean.
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Almico
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#16: Post by Almico »

GC7 wrote:That was a cool demonstration that illustrates the point somewhat. I'm not sure water may be more insulation then density but it did make the point.
Scott mentions in his new book that although higher moisture content should promote heat transfer, its evaporation retards heat to the point that moister coffee requires more heat to roast.

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GC7
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#17: Post by GC7 replying to Almico »

Every Sumatran coffee I've had was above average in moisture content. They all roast slower given the same heat/energy application to the bean. Perhaps this is an example of Scott's theory.

archipelago
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#18: Post by archipelago »

I use density (ISO bulk fill density method specifically) for my forecasting of fade. For roasting it's one indicator I take into consideration with moisture content and aw. Seems to influence how the coffee takes on heat before crack, in particular

Rickpatbrown
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#19: Post by Rickpatbrown replying to archipelago »

Sorry, I dont understand all these words :|
Fade?
Aw?

Please enlighten me.

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