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Drum material: which is the best
I would like to hear your opinion about the best material to use for a drum roaster.

I quote from a roaster manufacture document:
"..... we use carbon steel because it contains the best of these metallurgical properties, is durable longterm
and cost effective. Many people think stainless steel or cast iron is better however this is not the
case in regards to "evenness" of retaining and disbursing heat across the entire drum and transferring
that evenly inside the drum to the bean. This is also a fallacy as stainless steel is not as effective because
it is a reflective metal that dissipates the heat differently and cast-iron is a porous metal that has uneven
Since cast iron is "poured' in to a mold, the density is not consistent throughout and therefore the
thermal dynamics of heat transfer is not even. Carbon steel is rolled and the density is consistent in its
thickness - the result is "evenness" in the thermal dynamics of heat transfer. Please note however, the
steel used and the engineered design of the drum is only one element of consistency in a ... roaster."

Thanks for your opinion.
I like carbon steel, it's cheap easy to and work with. Stainless is great, just expensive and harder to find. When I built my drum I used a piece of steel pipe and am happy with how it roasts. I would not use cast, hard to work. This is a controversial statement but I think any heated metal will roast beans the almost the same. One will gain heat and give up heat a little different than the other but you will adjust to these differences as you run the roaster. So use what you can find and what you can weld.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
Plain steel, either hot- or cold-rolled is fine. I see no reason to spend more for carbon or stainless alloys unless you find a good buy on them. CRS (cold-rolled steel) is your most likely bet for perforated metal.
This is a complex question to properly evaluate. In addition to the items mentioned here , I like the insurance of a stainless drum because if any corrosives or contaminants (ie plastic, rancid build-up,mold spores,other organic contaminants)( many molds can withstand the temperatures of roasting and can contaminate the product) start to taint the taste of the product coffee. ss can be cleaned to like new condition to remove the taint and get back clean conditions with less risk of corrosive damage to the surface of the drum. Many claim that seasoning of the drum is very important to the taste of the product. I have found that to be a non-issue with a ss drum. There are thermal performance differences and cost differences for sure. The thermal differences are no as important to me since most of the roast heat transfer is convective (in drum roasters) but they can be a bother if you are starting the roast with a high preheat or employ steep temperature transitions within the profile due to scorching concerns. Is ss worth the difference in cost? If you encounter tainting of your roasts due to contamination, it provides some flexibility to recover without damage to the drum. For me tast is king so I gladly pay the premium for this flexibility All other problems notwithstanding.
best material totally depends on if you have the tools to work any of the three materials.

Steel or Iron will be your easiest to work with,

Stainless steel unless your willing to pay out some really high bucks, all your getting is some iron with a high nickel ot chrome precentage, and your going to pay big time of that percentage,
Cast Iron depends on who poured the iron and will likely take a lot more heat evenly then either of the other two, as far as the density of the cast, depends again on who poured it.

If I was going to build a drum roaster larger than 12 inches and I could get it poured I would use a cast iron drum.

Its also as easy to clean as stainless steel

If I was building a 300 kilo commercial machine I would probably have it made out of stainless steel to get around a bunch of goverment health regs.
I pour Iron and roast Coffee BeansThumbsUp
If life seems normal your not going fast enough Mario Andrette
I agree that the material isn't a huge factor except for how difficult it will be to fabricate with your tools.

Since the beans are moving around at quite a clip the heat exchange rate differences due to casting irregularities (cast iron) or differences in other metals is much less of an issue compared to the thickness of the drum. Going too thick can cause challenges due to slow response when trying to follow a profile with steep curves.

1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Plain steel is carbon steel. For a drum roaster Mild steel also called plain steel or carbon steel is the way I have gone. Cast iron is probably too difficult to get in the size you want and for little gain. There is IMO no practical reason to go for SS.
VBM Minimax 2gp, 1gp Reneka Techno, 2 gp la Pavoni Pub, la Cimbali M28, SJ Maz, FB 6kg HM roaster and other stuff


allenb wrote:
I agree that the material isn't a huge factor except for how difficult it will be to fabricate with your tools.
Since the beans are moving around at quite a clip....

Well, what are your thoughts about copper?

I read all the mentioned metal and alloys properties on wiki...and it looks like copper is the best for thermal transfer rate, it is a metal and not an alloy and is easily recyclable (sustainable material)

I'm Italian and you know how we love food: let me tell you that the same food cooked on different pan (copper, aluminum, stainless steel, ceramic, teflon, etc) will taste fairly different. The most upscale restaurants use copper pans!

But I'm here with an open mind to hear your thoughts.

well I hate to say it but if your planning on copper I hope you have a very large build budget.

Copper is one of the most expensive materials that a builder of homemade coffee roasters could think of for the drum, in thin sheets for the outside skin I would say yes. But copper will not stand up to the abrasive action of the beans sliding on it.

somemore info on what your wanting to build might help other in your search for a drum material, there have been people on here that have build everything from a 1/2 pound roaster to a 20 pound drum. Most are made of what is termed Mild Steel or A-36 if your talking plate, steel is simply Iron that has had most of the carbon removed and additives added to change the grain structure of the material to aid in the tensiel strength of the material and other properties such as abrasion resistance.

RK Drums used perferated stainless steel in there drums, a small 5 lb drum from them cost in the range of 250 dollars I belive I haven't checked their prices lately.

Are you able to do the Fabrication work yourself, if not then the cost of your roaster just went up by a factor of 5 or more.

Copper works great for making white sauce, but so does cast iron or stainless,

some idea of what your wanting to build would help?
Edited by dja on 01/16/2011 9:30 AM
I pour Iron and roast Coffee BeansThumbsUp
If life seems normal your not going fast enough Mario Andrette
I'm not sure why some are saying iron is easy or a practicle solutions for the DIYer. Unless you know how to make foundry patterns (I do) and have access to a foundry, you aren't going to be making a homemade drum with cast iron.

If for some reason you really want to to with iron, then check out ductile iron round tube. It is used a lot for well casings and sewer pipe, although you'll need a large metal lathe.

Your best bet is low-carbon steel sheet. You can get a sheet metal shop or metal fabricator to roll it into a tube for you.

Koffee Kosmo


I would like to hear your opinion about the best material to use for a drum roaster.

My preference is carbon steel as noted above


Well, what are your thoughts about copper?

Join 2 old but thick copper pots together and you have a drum


I home roast and I like it. Designer of the KKTO
Roaster Build information
Blog -

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
What about this for copper?
Edited by allenb on 01/03/2017 8:29 PM
Depending on size drum, you can buy a piece of copper tube 6"x12" for $140 or 8"x12" for about $260. Anything larger than that and you can probably buy a drum roaster already build cheaper.

I kept thinking about copper for a .5K to 1K drum roaster but since I happen to have a 8ft long section of 6"dia stainless pipe that has about a 1/8" wall, most likely it's drum will be SS.
Not to hijack a post but quick question.
If I cut that piece of SS into lengths and sold on ebay for drum roaster projects, what would be a good length to make the pieces? I've had it for 20 years just laying behind a shed and I think it goes for over $100 per foot now.
Smokin Joe
So if someone say wanted to go the double wall route... and feeling especially masochistic, in the pursuit of perfection, was considering an iron outer drum with a carbon inner layer then what kind of thickness ratios would one be looking at layer wise? The suggestion for the ductile iron round tube seems like a good starting point and then fabricating a carbon tube to fit inside the iron tube.

How much of an air gap, if any, would one want between the iron tube and steel tube? Would one go thinner than 12 gauge steel thickness since the iron is there as a heat shield of a sort? Would going thinner help keep the inner drum more responsive in spite of the outer drum's mass? Would one go thicker to help offset the thickness and mass of the iron layer, counterintuitive? Would the air layer be more dependent on the outer drum thickness or the inner drum or is there a nice conceptual ratio of iron to air to steel that encompasses all three.

In the few pictures I've seen it looks like the outer iron layer is much thicker than the inner layer but my eyes are not what they used to be.... is this an optical illusion?
Edited by Smokin Joe on 10/20/2018 12:03 AM
Carbon inside an oven... please can you detail ?
Which purpose, and how you apply the carbon stuff ?
I have experience with carbon fiber layup only, and I don't think it apply in this case... :confused:
Carbon steel has about 3X the thermal conductivity of stainless in the 200C range. You would think it would provide more even distribution of temperature.
So many beans; so little time....
Ah, steel, not fiber Grin got it...
For my project I'm using a 3mm carbon steel drum and have cut some 0.7mm stainless sheet to wrap around it with some packing as an attempt to replicate the dual skin effect. At least that's the idea - it's probably overkill.
Partly it's also as I don't intend to implement a flame baffle.


dmccallum wrote:

For my project I'm using a 3mm carbon steel drum and have cut some 0.7mm stainless sheet to wrap around it with some packing as an attempt to replicate the dual skin effect. At least that's the idea - it's probably overkill.
Partly it's also as I don't intend to implement a flame baffle.

If your talking about ?packing? as insulation; wouldn?t it defeat the intended purpose? Coffee-Tech Engineering builds several different layered drums, one has copper and some with perforated layers.

Wouldn?t it be easier to build a heat shield? I recently saw a 1k roaster with ribbon burners and a heat shield that works great. He?s done quite a bit of experimentation with burners and drums, a lot of time consuming work vs going with a more standard type construction.
I know this is an old post, but my question seems to fit here the best and i cannot ind the answer elsewhere. I regards to the type of material, which would be the easiest to maintain? I have a friend who is and awesome fabricator and can fab any of the options other than cast iron.

Im looking to build roughly a 1 kilo maybe 1.5. I rost mainly on my back porch and im worried about rust build up on regular steel. However i dont want to spend on SS we can probably build the drum out of regular steel for free.
Cast iron rust too... if not conditioned, as the frying pans are seasoned with oils Grin
In a coffee roaster the oils inside the beans will do the drum conditioning after 5-10 roasts.
so mild steel shouldnt have many rut issues as long as it is used occasionally?


BeefTips wrote:

so mild steel shouldnt have many rut issues as long as it is used occasionally?

It will be ok after you season it. I used a piece of well casing for my drum and after 5 two pound batches it has a nice patina on it.
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