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My Whirley Pop so far and a potential future mod.
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Discussions > Coffee > Home Roast > My Whirley Pop...  
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TheoDickson
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Joined: 27 Apr 2014
Posts: 8
Location: Bristol
Expertise: I love coffee

Posted Mon Jun 16, 2014, 12:29pm
Subject: My Whirley Pop so far and a potential future mod.
 

I've got a Whirley Pop that I've been working.  
http://i.imgur.com/iZOYd23.jpg
I've got an oven thermometer set onto a wooden block to insulate it.
http://i.imgur.com/hUek7BA.jpg
It also helps to stabilise the probe.
http://i.imgur.com/rObM6SK.jpg
The cast iron pan generally stabilises the thing as I crank it, and helps with heat distribution.
This is giving me great roasts. Doesn't do so well with delicate beans/lighter roasts though. The roast doesn't even up until later on. I think if I was able to introduce some convection I could fix that. My plan is to figure a way to rig it to stand a few inches above the bottom of the skillet and then perforate the entire base of the Whirley Pop with small holes. Might this do the trick or would I be risking ruining what's currently a decent setup?
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z0mbie
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z0mbie
Joined: 26 Sep 2013
Posts: 346
Location: Online
Expertise: I live coffee

Posted Tue Jun 17, 2014, 10:25pm
Subject: Re: My Whirley Pop so far and a potential future mod.
 

I don't mean to be a naysayer, so please don't take it this way.. I think your plan is very problematic, IMHO.  First of all,  you've eliminated the conductivity of heat from the cast iron skillet to into your roaster by raising it off the skillet.  At half an inch (much less a few inches) I'd be surprised if the beans even get hot enough to roast to any noticeable degree.    Second, punching holes on the bottom will allow chaff to exit through on the bottom of the pan, and without being stirred the chaff will allowed to burn in place on the cast iron surface, even potentially igniting.

I think you've got a decent setup.  The keys to achieving an even roast are: 1) Stable high ambient temperatures for indirect heating of the bean (eg. high roasting temperatures that surrounds the bean). 2)Effective agitation (eg. tossing the beans).

I started out with WP, but quickly developed my own roasting hand roasting method (jiffy pop style roasting).  

If you're happy with your current setup, stick with it.  I think it's probably the best you'll get out of WP roasting.
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TheoDickson
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Joined: 27 Apr 2014
Posts: 8
Location: Bristol
Expertise: I love coffee

Posted Wed Jun 18, 2014, 2:42am
Subject: Re: My Whirley Pop so far and a potential future mod.
 

Thanks for the advice. As it turns out, I'm already part way through doing this! I figured if it didn't work, it won't break the bank to get myself another one. No reward without risk I guess. Anyway, I found a different cast iron pan (a thick old Le Creuset) in the garage that the Whirley Pop snugly wedges into, leaving roughly a 1.5 inch gap at the bottom. Hopefully the contact around the sides will solve the very valid problem you raise about the conductivity. You are right though, I'm going to have a chaff problem. Damn, did not think about that. If it's really that bad, I guess it's Whirley Pop no 2 or maybe just rig the lid to a different pan. Not a big fan of the aluminium one that comes with it anyway.

Edit: Also, what in particular will be so bad about chaff ignition? Just loads of smoke (and could this smoke taint the beans) or might it actually get dangerous?

Edit 2:

z0mbie Said:

I started out with WP, but quickly developed my own roasting hand roasting method (jiffy pop style roasting).  

Posted June 17, 2014 link

Funnily enough I came up with something very similar before I got the Whirley Pop and I was just experimenting with the oven and various pans. The iron skillet in the pictures is double handled and has a lid . Every 15-30 seconds I would hold both handles and press the lid down firmly while vigorously shaking the whole thing. Far better than stirring as you say in your thread about it.
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TheoDickson
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Joined: 27 Apr 2014
Posts: 8
Location: Bristol
Expertise: I love coffee

Posted Fri Jun 20, 2014, 8:17am
Subject: Re: My Whirley Pop so far and a potential future mod.
 

The mod is complete. It roasts amazingly evenly. No scorching whatsoever.  And very easy to control temperature. But the chaff does indeed fall through the holes and burn up. As a consequence I've detected a significant ashy note in the three roasts I've done so far, even though they were taken not far past FC. On the light side of medium for sure. I haven't been opening the lid at all during the process as I can profile pretty effectively by time/temp/sound/smell so perhaps opening the lid periodically to let the smoke out might help? Otherwise I'm going to cover the bottom with foil and try again... if that eliminates it I know my problem. In that event, the only idea I have to stop it while still keeping the current design would be fitting some sort of mesh screen to hold the chaff off of the cast iron surface. Can't see how it would hurt but obviously may not stop it either. Anyone else have any ideas?
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z0mbie
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z0mbie
Joined: 26 Sep 2013
Posts: 346
Location: Online
Expertise: I live coffee

Posted Fri Jun 20, 2014, 10:50am
Subject: Re: My Whirley Pop so far and a potential future mod.
 

TheoDickson Said:

The mod is complete. It roasts amazingly evenly. No scorching whatsoever.  And very easy to control temperature. But the chaff does indeed fall through the holes and burn up. As a consequence I've detected a significant ashy note in the three roasts I've done so far, even though they were taken not far past FC. On the light side of medium for sure. I haven't been opening the lid at all during the process as I can profile pretty effectively by time/temp/sound/smell so perhaps opening the lid periodically to let the smoke out might help? Otherwise I'm going to cover the bottom with foil and try again... if that eliminates it I know my problem. In that event, the only idea I have to stop it while still keeping the current design would be fitting some sort of mesh screen to hold the chaff off of the cast iron surface. Can't see how it would hurt but obviously may not stop it either. Anyone else have any ideas?

Posted June 20, 2014 link

That's great.. well let's take a photo and see what the whole thing looks like? I'm curious as to how far the pot is from the cast iron skillet.  As I stated in my post I was quite skeptical you could get enough heat to roast but apparently you're getting outstanding results.. So I want to see the distance.  I'm still doubtful it's "a few inches".

Anyway, regarding the chaff issue. The problem is the chaff does not receive agitation sitting in the heat and therefore burns. Whether it is sitting directly on the skillet or on the mesh makes no difference, so if you're getting roast-level heat transfer from skillet to the pot to roast the coffee, I don't see how the a mesh will help, but then again, try it maybe it would work, it's simple enough to do.. I don't mind ever being proven wrong as it is gained education :)

BTW, did you ever see my chaff collector method?  it's a shop vac and a plastic container with holes on the lid.  It's a wicked idea :)
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TheoDickson
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Joined: 27 Apr 2014
Posts: 8
Location: Bristol
Expertise: I love coffee

Posted Fri Jun 20, 2014, 2:45pm
Subject: Re: My Whirley Pop so far and a potential future mod.
 

z0mbie Said:

That's great.. well let's take a photo and see what the whole thing looks like?

Posted June 20, 2014 link

http://i.imgur.com/p2hsBww.jpg
http://i.imgur.com/Gpwpvw7.jpg
http://i.imgur.com/47dIDA8.jpg

The last one is the Whirley Pop held above the pan for reference. It's wedged in two inches and the pan is 3.5 inches tall so it's about 1.5 inches above its surface. As you can see it's likely that much of the heat is thus coming from the sides and not below - perhaps this the cause of the even roast not airflow?

Just did a few more batches. I propped open the lid to vent the smoke through. Before this I would hit first crack at 5-6 minutes/180C, clear it at 7-8 minutes/190C and pull the roast about a minute later at 190-195C. Lid closed the whole time.
Now with the lid open the temp is reading much lower. This fooled me the first time and I added too much heat, hit first crack at 4.5 mins/170C, finished the roast at 8 mins nearing SC. Tasted awful, still ashy. So the next one I had the lid really far open and the flame lower. Hit FC at 7.5 mins/148C. Cleared it at 9 mins/156 and pulled it at 10 mins/156. Here's a pic of this batch (80g Kenya Peaberry) and the burned up chaff left over - maybe someone will have an inkling as to whether this is enough to ruin the batch with its smoke!

http://i.imgur.com/4YtejIl.jpg
http://i.imgur.com/n91qHQ0.jpg

I need to figure out the cause of the lower readings/faster roasts. Is it simply that nothing much is changing about the roast as it's mostly conduction but I'm lowering the air temp, or is there airflow happening that's allowing roasting at lower temps. Maybe even a bit of both.

z0mbie Said:

BTW, did you ever see my chaff collector method?  it's a shop vac and a plastic container with holes on the lid.  It's a wicked idea :)

Posted June 20, 2014 link

No I haven't seen it but I'll check it out. Need a cooling system soon. Metal colanders seems to be sufficient for small amounts but I'm running a coffee society at my university next year so I need to be able to do big batches!

Update: Just cupped the pictured beans. Ashy and bitter, like a bad dark roast. Could that chaff really be doing all this? Seems increasingly likely. They roasted nowhere near as fast as previously and looked better too, but virtually no change in the cup.
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z0mbie
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z0mbie
Joined: 26 Sep 2013
Posts: 346
Location: Online
Expertise: I live coffee

Posted Fri Jun 20, 2014, 7:03pm
Subject: Re: My Whirley Pop so far and a potential future mod.
 

ahhh.. that explains it.. the first pic in the thread showed significant  diameter difference from the bottom of your WP with the skillet, so I assumed you were going to use the same skillet when raising it a few inches.   As such I presumed doing so will basically allow all of the heat to vent out sideways.  But in your actual revision, you swapped out the skillet with a cast iron pot with approximately the the same diameter opening as the bottom of your pot, thereby allowing a tight seal, retaining the heat transfer completely. Makes total sense now :)

Anyway, given the seal the smoke (and carbon) from the burning chaff has no where to escape but back through the holes in the bottom of your WP. As a consequence the carbon might have tainted your beans? Dunno but if so, that's a real shame because the roasts looks real nice.  Thing is, there's always smoke in roasts, so I'm a bit confused that the smoke from the burning chaff could foul up the roast.   I mean, my jiffy pop method is entirely enclosed.. so the whole roast is bathed in smoke the whole time.. but my roasts are fine.  OTOH, In my JP roasts nothing is burnt really, so perhaps it's not so much the smoke as it is the carbon from burnt chaff.  Really don't know.  Could just be that you roasted it too long?
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TheoDickson
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Joined: 27 Apr 2014
Posts: 8
Location: Bristol
Expertise: I love coffee

Posted Sat Jun 21, 2014, 2:54pm
Subject: Re: My Whirley Pop so far and a potential future mod.
 

Tried several more roasts, varying lengths, times, final roast level, lid quite far open. Managed to reduce the ashiness a good bit with one that hit first crack in 11 minutes, finished at 14, so that the result was just about drinkable but its not ideal at all. So I've shelled out for Whirley Pop number two. Will repeat with the new un-holed pan. I'm really starting to think the evenness is largely due to the wedged-in set up and not remotely related to the holes so I as well as eliminating the ashiness I'll probably retain the evenness anyway. Along side that I've got a few ideas for what to do with the spare lid. Will report back soon!
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TheoDickson
Senior Member


Joined: 27 Apr 2014
Posts: 8
Location: Bristol
Expertise: I love coffee

Posted Mon Jun 23, 2014, 7:48am
Subject: Re: My Whirley Pop so far and a potential future mod.
 

Well I've done three roasts with the new Whirley now and not much has changed. I've definitely got a lot to learn! Perhaps my beans are subpar too? I would really welcome any ideas on what causes roasts to taste ashy, thin and bitter when they are pre-second crack with no charring or chaff ignition.
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