HomeRoast Digest

Topic: Drum Roasting Problem--Need Advice (27 msgs / 833 lines)
1) From: DeCambre.Peter
I will be out of the office starting  11/26/2002 and will not return
until 12/02/2002.
I will respond to your message when I return.
homeroast mailing listhttp://lists.sweetmarias.com/mailman/listinfo/homeroast

2) From: Gary
Hi Everyone,
I am having some trouble with larger roasts on my drum roaster.
I usually roast 1/2 lb batches and get to first crack in 10-12 minutes.
If I am going for a FC, I run it about 1-1.5 minutes past the finish of
first crack.
I have tried to roast a 2 lb batch twice now and have had the same problem
twice. I can't seem to get them to first crack even though I keep them in
over 20 - 22 minutes. The beans seem to be baked but not burnt. I use a Zass
169G to grind my beans and both times when I have done the 2 lb batches, the
beans are very hard to grind. I find that beans roasted to a FC+ or longer
are usually softer when grinding.
I would be happy for some advice.
My set up is as follows:
Weber 3-burner genesis gas grill
Digital thermo-couple from Sweet Maria's, so I know my temps are ok. The
probe is located at the centerline of the drum, near the end.
35 rpm motor
Home made drum from perforated brass, 6" diameter by 14" long with 4 each,
3/4" vanes inside
I always preheat to 500 degrees
Load beans and monitor temp to get to 470-480 in 5-7 minutes and then hold
in that range until first crack starts.
Like I said, with the 1/2 lb batches, no problem with first crack.
I can't seem to get the 2 lb batches to first crack even after 20 minutes at
Any suggestions would be appreciated.

3) From: Aaron
Gary one thing when I was experimenting with my home brew roaster 
earlier this year is, even though the outside temp is up to par, 
sometimes it don't make it to the inside of the drum with the beans very 
A small screen size (to keep the beans in) will kill a lot of the heat, 
(at least I have found in my setup) and while yes the metal itself may 
get up to temp, the air / atmosphere inside the drum might not, so only 
the beans actually touching the sides are getting the heat for the short 
time they are touching before it rotates and they tumble.
I ended up using a bit of convection in my make up, and putting vents on 
the sides for the hot air to blow in to heat the entire process up.  If 
you don't have convection by forced means, ie a fan or something of that 
nature natural convection can help too.
To be honest, I have absolutely NO idea if this is making a difference 
with your setup or not, Id have to see it and take a good look to get 
any ideas, but am throwing this out as a possibility of something to 
look into that might help your setup.
Also, yes, the 'baking' the beans is exactly what I had happen, and they 
eventually did get up to temp but did so too slow I am assuming and 
well... I didnt hear many first cracks at all and came within a 
heartbeat of hitting 3rd crack when I took the thing out after 22 
minutes and put it in front of a fan to cool down. 
I ended up making ammends for more circulation and sticking to smaller 
batches to solve my problem.

4) From: Eddie Dove
Never thought about it that way ... thanks for the insight, Aaron.
On 11/24/06, Aaron  wrote:

5) From: Gary
I'll see what I can do about more air flow or possibly a higher temp to
start out.

6) From: Jeff Oien
I'm eventually at 600 degrees to get to first crack in
12 minutes with 1120g or so to end up with a 2lb batch.
I know that's a lot higher than what other
people have posted in their profiles for the RK drum but
that's what I need to get there. I have a Charbroil grill,
can't remember which model at the moment. My thermometer
is right in the middle of the grill as prescribed.
Gary wrote:

7) From: Connelley Barton
This is basicly where I end up in temperature on my RK.  550 deg. for 16 
min. 1^st crack, and 570 deg. for 14 min. 1^st crack.  I have roasted 
for my wife's small coffee shop with my RK for the past 2 years, and 
customers are very enthusiastic about our coffee.
I don't think the indicated temperature is as important as the length of 
time it takes to get to first crack.
Jeff Oien wrote:

8) From: Matthew Evans
I have almost the same set up as you, and run about the same tem=
ps too, except I try to get my 470-480 established in 2-3 minutes.  The onl=
y other difference is that I have a 60 RPM motor.  I started out with the 6=
 RPM standard rottisserie motor and was able to get 1/2 pound barely roaste=
d, and it took a long time.  When I found my 60 RPM motor, it made a huge d=
ifference.  I could do 1/2 pound batches in 8 to 12 minutes and 2 pounds in=
 13-17 minutes.  I found that the ability to get an even roast had everythi=
ng to do with how fast I was turning the drum.  Not sure what the differenc=
e between 35 rpm and 60 rpm would be.... but it might matter.  Hope that he=

9) From: Ed Needham
Your thermometer is giving you false readings.  Crank that puppy up on high 
and let it warm up for about 10 minutes, add drum and see where the cracks 
occur.  Cut back heat to give you a roast that finishes in 15 to 20 minutes 
to second crack.  That will be a good starting place.  Note where the 
thermometer reads doing it this way and use those readings as benchmarks, 
ignoring the numbers.
Ed Needham®
"to absurdity and beyond!"http://www.homeroaster.com(include [FRIEND] in subject line to get through my SPAM filters)

10) From: Scott Marquardt
You're not getting proper agitation at all. Not with that drum size, those
vane dimensions, that RPM, and that quantity of beans.
If your temps are high enough, you're just not getting sufficient exposure
of each bean to the BTUs you need to transfer to 'em. That's not even in
doubt, really.
A rolling mass of beans will take forever to heat compared with a nicely
flailing, flying, aerborne spray of beans.
If you succeed with improved agitation, you'll find your interior air
temperatures a lot lower than they are now, with your current temps. That'll
be the first sign that your revisions are successful!
- Scott
On 11/24/06, Gary  wrote:

11) From: Ed Needham
I think taller vanes might help, but I've made drums with vanes that small 
and I did not get the result Gary was getting.  I'd expect a very uneven and 
scorched roast if the vanes were not doing their job.
30 RPM worked fine for me for quite some time, and I got little from going 
to a 57 RPM motor except for a little time off the length of the roast.
Ed Needham®
"to absurdity and beyond!"http://www.homeroaster.com(include [FRIEND] in subject line to get through my SPAM filters)

12) From: Gary
Hi All,
Thanks for the great advice and suggestions. Here is an update.
I am quite sure my thermocouple/ thermometer is working correctly. I checked
it in boiling water and it has been very consistent with each roast. I am
pretty sure this is a heat transfer issue with the larger batch sizes.
I forgot to mention in my first post that I have a cookie sheet on the lower
grate acting as a heat diffuser.
Also, when I built the assembly, I spoke with Ron Kyle and he suggested
either the 35 or 60 rpm. I opted for the 35, didn't really have a reason.
I did try another 1.5 lb roast today and it worked out pretty good.
I used the following technique.
	I Removed the cookie sheet.
	Preheated to 520-530
	Loaded up the hot drum and dropped the beans in and put it back in the
	Kept the temps at 480-510 rather than 470-480 like I normally would; temp
control was a little more sensitive without the diffuser.
Got to first crack at 16:25, opened the lid and turned down the heat. Pulled
the beans at 18:15. They looked pretty good and they taste good too, tried
an aero press this evening.
The first crack was a rolling crack like I had been expecting earlier.
I then turned around and roasted a 1/2 lb batch like I normally would,
preheat to 500, load and ramp to 475 in 3-5 min and hold at 475.
My take away from this is the larger loads are not getting the heat
transfer, either because the temps in the grill are not high enough or the
beans are not in contact with the outer surface of the drum long enough or
they are not being agitated and thrown around inside the drum. A higher rpm
would increase the stick time due to the added centrifugal force. Seems
reasonable as I get a little concerned about roasting at 500-515 due to
possible scorching of the beans. If I wanted that I could just go to the
local Charbucks.
it may be that larger vanes would keep the beans in the air more and allow
for a quicker heat transfer.
I know that I can push the beans to first crack by turning up the heat. I
think I will make the vanes about 1.5" and see if that takes care of the
I will also order up a 60 rpm motor and see how it compares.
Thanks all, I'll keep you posted.

13) From: Bob
Needed to do a couple of 2# roasts today which I do rarely.
Preheat to a solid 550 F, load and recovered to 500F within 2 minutes. 
500-505F roast, rolling 1st at 13:00, end of 1st 14:30. Pull and cool 16:00. 
City+ to full city. I think my diffuser plays a big part in quick recovery 
time, leading to a less extended roast if that's what you are after. 
Followed RK's advice to the letter when building the diffuser and believe 
its heat sinking ability leads to faster recovery and a stabilization of 

14) From: Jeff Oien
I think it's simply a matter of turning up the heat. It sounds like
you're over thinking this. I don't think you'll scorch the beans in an
RK drum unless the flame is way up into the drum.
My 600 degrees first crack in 12 minutes figure is with a 60 rpm motor.
Gary wrote:

15) From: RK
Tuned in late on this one, I was all day building a 10X14 shed.
Gary, its all about the heat, although 3/4" vanes do seem a bit small for 2 
lbs loads. But if you get the heat right it still should produce a good 
roast in a time frame of 14 to 16 min. There are two things that can happen 
doing larger batches.
If you use the same temps as smaller batches the roast times will lengthen 
and if the temps are too low the beans will bake instead of roasting.
Larger loads need more heat to keep times near the target.
Smaller loads require less heat to get to that same target.
I really like 50 to 60 rpm motors especially with larger loads.
Ed had a great suggestion. CRANK_ER_UP.
Temps are relative to various things. The thermometer you use, the grill you 
use, and most important is the placement of the thermometer. The further you 
go away from center of your drum effects the temps, resulting in the need 
for higher temps. I have mind dead center of the drums length and diameter. 
I do 1 lb at 430, (8 to10min), 2lbs at 460, (12 to14min), 3 lbs at 490, (15 
to17min), and 4 lbs at 510.(18 to 20 min)
I use a 36K fiesta grill and a 12 gauge sheet metal diffuser with 1.5" of 
space all around for air movement.
I have one customer whose temps are abut 40 degrees higher then mine to 
achieve the same results, so temps are just a guide line and you have to 
experiment to find the correct temps for each size batch that will get you 
to your target.
I stop a city roast right after 1st crack is complete,  I know the time for 
this, say 14 min.
I stop full city just at the first hint of 2nd, say 17 min.
 I judge this by knowing that when first stops so does the smoke and when 
the  smoke starts again 2nd will happen 15 to 20 sec. later.
A city+ is dead in the middle of the time for city and full city, in this 
example that would be 15.5 min. This will change with temps, batch size and 
the bean I'm roasting.
It takes practice and notes as each grill, is unique.
each bean is unique and it depends on how fussy you are with your roasting. 
Profiling is a learned technique that takes lots of practice and lots of 
Generic roasting is easier but does not give you the best results for a 
particular bean, although it will still be good to great coffee, and if the 
truth be kown is the method most home roasters and even a lot of 
professional roaster use.
CRANK-ER-UP Gary and start taking notes.

16) From: Scott Marquardt
I'll chime back in to argue, in a friendly way, that raising the ET isn't
the ideal way to deal with this. An ET should, itself, be a goal -- not just
a means. More effective agitation to preserve ET and yield a good profile is
a superior approach, IMO, to letting the ET drift with a need to make it
work with whatever agitation a large batch of beans happens to experience
with a given physic in the drum.
The question is whether ET matters. I think it does. My expertise and
experience with drum roasting doesn't approach yours, but I've existentially
decided that ET is going to be less negotiable in my roasts than I once
thought it might be.
two cents.
- S
On 11/25/06, RK  wrote:

17) From: Ed Needham
I would be very confident to say that the thermometer you are using is not 
accurately reflecting the heat inside your drum.  It may need to be shielded 
better from direct heat or maybe re-positioned.
I preheat to 350F as measured by my thermometer, then let temps rise to no 
higher than 470F.  I can roast five pounds in less than 20 minutes to second 
I'd get rid of the cookie sheet and if diffusion is needed on your grill, 
then use something a bit more porous.
Ed Needham®
"to absurdity and beyond!"http://www.homeroaster.com(include [FRIEND] in subject line to get through my SPAM filters)

18) From: Ed Needham
I'm pretty sure, with the results reported, that the ET is severely low, 
regardless of the temp readings.  Higher ET will allow him to go through the 
roasting benchmarks, then he can note where they are in relation to the 
thermometer readings and go from there.
It's all about the bean.
Ed Needham®
"to absurdity and beyond!"http://www.homeroaster.com(include [FRIEND] in subject line to get through my SPAM filters)

19) From: Aaron
Also the ET is the easiest variable to control or change in the 
process.  He already has had some satisfactory results, so this tells me 
that he CAN tweak ET for what he needs.  or at least until he 
understands it a bit better gets it stable then can tweak other factors 
to fine tune it.
As was said earlier, each roaster has it's own quirks, just like the I 
roasts many of us own, there is no set ... do it at *this* temperature, 
because they all act their own quirky ways.
The beans themselves vary enough that 14 minutes to xx temp might work 
with one type of bean but it might take 15 for the next bean to hit that 
temp... all other things considered similar.
Also I am thinking, the beans have some moisture in them, it's going to 
take a lot of latent energy to steam them off prior to first crack... 
that's heat that will have to pass through the barrier of the metal 
drum, the atmosphere inside the drum, into the bean and do it's thing... 
more beans means much more energy needed.. what is the heat transfer 
rate through the drum material??  if it's lacking then more heat will be 
needed outside to get enough of it inside, hence  higher temperatures.  
I can't remember my formula's but I believe he said his drum was 
brass??  a bit different heat properties than stainless of the RK drum I 
am thinking. BTU's are very important, with proper insulation I can get 
that grill up to 600 degrees with a sterno can sitting inside it, but 
once we start using that heat to actually cook it's going to drop 
terribly fast and the can will no longer be able to provide enough heat 
to support the cooking process.  I might get away with cooking a beenie 
weenie but a ham now, good luck... ie bigger load, more heat needed.
While it is the easiest to measure, the heat outside the drum is not 
what is critical here, the heat on the bean is what ultimately matters.  
We use the ET as a gauge as to what we hope is happening internally and 
work from there.
I second the notion, crank the heat on bigger batches.

20) From: RK
This is a multi-part message in MIME format.
roasting 1 # of Malalbar. Heard first crack very well, then it really =
slowed down. I could hear a crack about every 15 seconds, then smoke =
started and rolling cracking started (I assume that was 2nd crack). I =
pulled it out and it was a fairly dark roast. On my fourth batch and I =
have not noticed much smoke during 1st crack. Is that unusual?
Smaller batches produce less smoke especilly during first crack. You =
will notice smoke even outside in the wind as 2nd starts.
Shoot for 4 min between the begining of first to the finish of your =
roast, getting this requires the correct temp.
If you are going from end of first then into 2nd almost immeaditly after =
the end of 1st your heat is to high.
Lower the heat as first gets going should help this situation.
I have ET for 1 to 4 lb loads. These are just bench marks and allows me =
to adjust the heat to get to these.
1lb  8 to 10 min
2lbs 12 min
3lbs 14 min
4lbs 16 min
these are times to first crack as it reall gets going not the 1st =
My target is 4 to 5 min from the start of 1st to the desired finish. =
This is less on city and city+ roast. 
The 4 to 5 min is when I go to Full City 4min and vienna 5 min and =
french 6 min.
I don't always hit this but I am really close most of the time.

21) From: RK
This is a multi-part message in MIME format.
The grill has been warmed up to what temperature? Has the drum also been =
warmed up? I am using a heat diffuser (12 gauge steel plate with 1.5 =
inches free around the edges). Is this slowing it up? I reached 1st =
crack around 11 minutes and that is with the grill pre-warmed up to 490.
This seems OK, I preheat my drum and grill to 500 and of course it drops =
to about 430 when I load the drum. Try reducing your heat as first crack =
gets going about 30 degrees. lower your controlls or raise the lid about =
2" I think you are close and only a bit of tweaking after first crack =
starts will get you the desired results.

22) From: Gary
This is an update to my drum roasting issues.
I removed the four 3/4" vanes and replaced them with three, 1-3/4" vanes.
Roasted 1 lb batch tonight and it came out just fine, very even color on the
beans. I started at 520, no heat diffuser, and then held it between 490-500.
Got to first crack at 16:20. Opened the lid for a bit and turned down the
heat. Pulled at 19:15, no sign of 2nd crack. I'm thinking this is about a
full city roast. I will let it rest and brew it this weekend. The temp was
hard to hold steady without the diffuser. I will put it back in for the next
I noticed that the sound of the beans in the drum was very different with
the larger vanes. I would describe it as the beans being thrown more and
tumbling less, if that makes any sense.
I will also pick up a 50-60 rpm motor and see how that affects the process.
Thanks everyone for your insights.
This list is terrific!
So much coffee, so little time.....

23) From: Brian Kamnetz
I look forward to hearing how the coffee tastes after some rest...
On 11/29/06, Gary  wrote:

24) From: Les
Roast was a bit on the long side.  You need to shoot for about a 15
min. total roast time.  Your faster motor will help a lot.  I would
give you my opinion on how the roast is going to taste, but I will
wait until your report.
On 11/29/06, Gary  wrote:

25) From: Scott Marquardt
I'll chime back in to argue  ;-)   that sufficient agitation to result in
efficient transfer of BTUs is more important than brute-forcing the ramp.
IMO, adjustments to roasters (where possible) should generally be in the
direction of increasing the latitude one has with variables -- not (where
not strictly necessary) in the direction of living with narrow limits on
Think of it this way -- if you want to brown your turkey when it's nearly
done you don't peel back only 1/4 of the foil and crank the oven to 700
degrees. You peel it all off and use a much lower temperature.
Heat on the bean isn't as much an issue as BTUs on the bean. If you had
rapid transmission of energy to the bean, you could probably have only a wee
lead of ET over bean temp. Not that that's what's desired -- but with great
agitation you could pour BTUs into the burner and have a low ET and the pace
of the roast would show it.
Yada yada.
- S
On 11/26/06, Aaron  wrote:

26) From: Jeff Oien
Scott Marquardt wrote:
However, if someone is trying to brown their turkey at 150 degrees,
wouldn't you tell them to crank er up as Ron Kyle said?
Unless there is something specific the original poster can
do to make his system more efficient.

27) From: miKe mcKoffee
Naw, 150f would be fine for the first 3 or 4 hours for a turkey. Especially
after a good 2 day herb and spice apple cider brined bath. On the smoker
that is before raising the temp to roasting temp:-)
Kona Konnaisseur miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:http://mdmint.home.comcast.net/coffee/Rosto_mod.htmUltimately 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.

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