Food safe roasting surfaces

[BlueChicago]

Hi Everyone,

I have been tinkering with the idea of building a small (1kg) gas fired roaster for a little while now. I have been intrigued by a number of roasters in this size range, but can't get past the desire to "knit" my own.

I have been digesting bits and pieces of information from the GCBC site as well as others, and have been unsuccessful in finding much information on food safe metals for coffee roasting (at least information that I could make sense of).

I understand that stainless is generally a safe material, but from a cost and workability perspective, can anyone suggest other options? 

Sorry for lurking for so long.

-Loren

[Ringo]

Normal steel is fine, stainless is fine, cast if fine.  I would never use any galvanized and would try to not use aluminum.  The coffee oils coat the roaster surfaces so the beans will not pick up the flavors of steel.  www.homeroasters.org If you have not been here go.  Lots of people building lots of roasters. You will see mine under Ringo Drum Roaster.

Ringo

[Tex]

Normal steel is fine, stainless is fine, cast if fine.  I would never use any galvanized and would try to not use aluminum.  The coffee oils coat the roaster surfaces so the beans will not pick up the flavors of steel.  www.homeroasters.org If you have not been here go.  Lots of people building lots of roasters. You will see mine under Ringo Drum Roaster.

Ringo

Why would you not use aluminum? As a conductor of heat it's hard to find a better material, although it's not so good at retaining heat. Steel & cast iron are good at retaining heat, but not so good at conducting it. Stainless is a poor option for either.

If I was designing a drum roaster I'd use 1/8" thick perforated anodized aluminum sheet.

[Ringo]

Just my personal preference, I would hate to try to defend the position.  I do not use aluminum pans or cups. For me I can not weld aluminum at home so that would be a problem for me.  Steel is cheap, strong, and easy to work.  I did make the outside skin of my roaster aluminum but no beans touch it.  I do drink beer that comes in aluminum but its ok to loose a few brain cells to get the Beer.

[Tex]

Just my personal preference, I would hate to try to defend the position.  I do not use aluminum pans or cups. For me I can not weld aluminum at home so that would be a problem for me.  Steel is cheap, strong, and easy to work.  I did make the outside skin of my roaster aluminum but no beans touch it.  I do drink beer that comes in aluminum but its ok to loose a few brain cells to get the Beer.

There are worse things to lose than a few of the little gray cells. Doesn't BPA lead to impotency?

[BlueChicago]

Ringo, I spent time going through your build photos and posts. Very nice roaster!

I've considered a number of items that could be used for a roasting drum, but an eight inch diameter schedule 40 pipe was not one of them. Very inventive. It is nice to know that it roasting well for you.

I am trying to get my arms around what types of normal steel I should consider. I see hot rolled, cold rolled, high carbon, mild, a variety of ASTM standards, and an alloy composition on some of these that kinda makes me nervous.

Does anyone know, outside of the cast iron spoked ring that I see on many of the commercial units, what type of steel they are using in their drums?

Thanks everyone for your input.

-Loren

[sea330]

I to have had concerns of roasting surfaces. Been roasting on a SC/TO for about 2 years now and in the first 6 months I roasted on the teflon surface of my Stir Crazy. it was starting to get burnt kinda bad, that stuff I am sure was contaminating my coffee so I decided to remove all the teflon with glass very fine grit blasting media and it pealed off in a few minutes then I polished the surface the best I could with steel wool and high grit sand paper worked perfect. I have researched Teflon and aluminum allot and Teflon is definately not for me and I hope you guys think seriously about doing the same thing I did. Aluminum as log as it isn't porous and polished up it should work well. I think if you were cooking 700 Deg and up on aluminum  may not be very good for you over the long haul. This is kinda serious stuff when we roast our coffee in our home made roasters. I apologize for my spelling errors and structure I am by no means a tech writer. Rich

[Tex]

I to have had concerns of roasting surfaces. Been roasting on a SC/TO for about 2 years now and in the first 6 months I roasted on the teflon surface of my Stir Crazy. it was starting to get burnt kinda bad, that stuff I am sure was contaminating my coffee so I decided to remove all the teflon with glass very fine grit blasting media and it pealed off in a few minutes then I polished the surface the best I could with steel wool and high grit sand paper worked perfect. I have researched Teflon and aluminum allot and Teflon is definately not for me and I hope you guys think seriously about doing the same thing I did. Aluminum as log as it isn't porous and polished up it should work well. I think if you were cooking 700 Deg and up on aluminum  may not be very good for you over the long haul. This is kinda serious stuff when we roast our coffee in our home made roasters. I apologize for my spelling errors and structure I am by no means a tech writer. Rich

Since Teflon on cooking surfaces is safe to 672°F, there's little danger from fumes. Some consideration might be given to ingesting Teflon, since the abrasiveness of the beans will cause some of the Teflon to rub off. But there are medical implants made with Teflon, so I doubt there a problem in that area either, or they wouldn't have gotten FDA approval.

Would I remove it if I had access to a sand-blaster? Sure, but I'm not getting OCD about it!

[Tex]

Ringo, I spent time going through your build photos and posts. Very nice roaster!

I've considered a number of items that could be used for a roasting drum, but an eight inch diameter schedule 40 pipe was not one of them. Very inventive. It is nice to know that it roasting well for you.

I am trying to get my arms around what types of normal steel I should consider. I see hot rolled, cold rolled, high carbon, mild, a variety of ASTM standards, and an alloy composition on some of these that kinda makes me nervous.

Does anyone know, outside of the cast iron spoked ring that I see on many of the commercial units, what type of steel they are using in their drums?

Thanks everyone for your input.

-Loren

I would bet the farm that not one metallurgist was consulted in the design of any roaster. If anything they consulted the sales staff of their supplier. I can almost guarantee they used the cheapest stuff they could find: low-carbon cold rolled steel; it's easy to form & weld.

[BlueChicago]

Not very comforting.

But, more justification to "knit" my own!!

[Ringo]

I think Tex is right, use what you can find.  Anything will work.  There are differences in heat transfer in different metals but you will adjust your roasting to how your machine roast.

[BlueChicago]

Ringo,

If you don't mind, could I ask you another question?

Based on your experience, what have you concluded is a "comfortable maximum" amount of beans to roast in your roaster (in pounds, roasted)? My understanding is that the drum on your roaster is: ID of 8" x depth of 12".

Thanks

-Loren

[Ringo]

I am just a home roaster, sell nothing but give a good bit away.  I like to have 4 or 5 different beans roasted at any time so I usually roast 1 or 2 pound batches.  For the first roast of the night I roast 2 pounds or less but after that every thing is heated up I can roast 6 pounds comfortably.  I have never tried more than 6 pounds but the way the beans move in the drum I think that is my limit.  I would say the best roast, easy to control the profile is 5 lb.  I have roasted 1/2 pound, but you really have to be careful with that.  Add a little too much heat and the roast goes too fast.  I will say if your metal working skills are limited like mine a smaller size would be harder to build.  Tighter places to weld.
Ringo

[BlueChicago]

That really helps. Thank you.

[jspain]

That really helps. Thank you.

Ringo is the MAN!!!!