Charcoal Grill Coffee Roaster




Introduction: Charcoal Grill Coffee Roaster

About: Designer. Thinker. Doer. Hiker. Lover.

It’s not exactly common to come across green coffee beans at the grocery store, but there’s a whole store in Oakland that sells them. As soon as I learned it was possible I had to try.

There are two components, the roaster and the spacer. I ended up making two versions of the roaster itself, but the spacer has worked just fine.

Like pretty much all of my projects, I made this roaster at Techshop. It's also included in my challenge to myself to Make 100 Things.


Step 1: Version 1 & Lessons Learned

I purchased steel hardware cloth from Cole’s Hardware and several pipe clamps to hold the cylinder’s shape. A simple threaded steel rod and some pipe caps finished off the roaster. I fitted the metal pieces at Techshop, mostly because I love working there but also because they have nice tin snips that made the work much easier. This could easily be done at home.

After the first roast, we found that 1/4” squares in the hardware cloth were too big for many beans (half of the Ethiopian beans spilled out as we were just about ready to put them on the grill) so we improvised for the day by lining the cylinder with aluminum foil. This worked well but left me looking for a piece with smaller openings to improve the roaster.

The spacer was a less obvious piece but necessary in my situation as the grill we are using is brand new and the steel rod would damage the sides. Depending on your grill, this piece could be optional. I took dimensions of the grill and whipped out a plywood spacer on the CNC mill at Techshop that has a channel for the rod and sits nicely in the bottom of the grill. If you're making your own, I suggest the following:

- Cut out a ring with space inside and outside the rim of your grill's bottom layer
- Provide a groove for the bottom of the grill to sit in. This will stabilize the spacer and keep it in place while roasting.
- Cut a channel across the center diameter of the ring for the steel rod of the roaster to sit in as it turns
- I put in a groove in the top for the lid to sit on as well, and I'd recommend against that. The lid will sit still on its own and if the lid is thin metal on the end like this one, if the lid sits in the groove it'll actually get in the way of the threaded steel rod spinning.

The wood, not surprisingly, browned due to heat exposure within the first two roasts so I wrapped the wood in foil for protection. The next improvements will be finding the hardware cloth with a smaller grid, possibly attaching a slow-speed motor, and protecting the wood. V1 also left me looking for a sturdier solution for the end caps as the fit was excellent with these pieces but the small beans finagle their way out.

Step 2: Version 2

Fun fact: Did you know as coffee beans roast, they lose water and
increase in size? Check out the photo of the green coffee bean and roasted coffee bean from the same batch above.

This second version has served us well for many roasts. Below is a list of improvements to the roaster, though the spacer has stayed the same with the addition of protective foil.

1. New wire cloth.

The first wire cloth had larger openings and some of the beans fell through the openings, so we lined the inside with aluminum foil. Functional solution, but it made checking the color of the beans throughout the roast more difficult and also kept the natural chaff from falling off during the process.

2. New end caps.

Stronger, longer, and much easier to drill into. I fixed one end cap to the steel rod and the other floated so that it was easier to remove and get the beans out quickly.

3. A window crank from my hardware store.

Simple solution (window crank and epoxy) that made the whole process a lot more enjoyable.

4. We put aluminum foil over the plywood cutout on the grill.

This was to protect the wood from the heat and seemed to work really well.

We also learned some things about roasting.

A. It’s darn near impossible to get the heat even in the grill, but after two roasts we got the idea to pick up the whole roaster and shake up the beans a few times throughout the roasting period to make sure all beans are heated more or less evenly. The photo above shows a person holding the roaster before it's hot but make no mistake - you'll want work gloves or at the very least kitchen mitts when you shake the roaster. Before we thought of this, the roast was all over the place - check out the photo above and you’ll see the whole spectrum of roasting from one of our first batches.

B. The grill should be level, or all the beans will end up falling to the low end of the roaster. (Seems quite obvious now.)

C. Roasting in a windy place can be handy. After we emptied the beans into a metal colander, I stirred the beans to cool them down and the excess chaff floated away. So with the help of my two viking gentlemen, we had a productive and relaxing afternoon of roasting. The high temperatures over four roasts left the little roaster that could with a gold tint, but it’s still seems perfectly in tact for future roasts.

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    15 Discussions

    Great tutorial. I've also been experimenting with roasting outside over campfire, charcoal grill and even a Coleman propane stove. I totally agree with your statements about inconsistent heat. I'd love to hear your results from putting a metal box above the charcoal to even out the heat.

    My roasts have been lacking in "brewability" and I believe what I've found is when the white line remains on the bean it shows a failure to crack occurred. (most likely 1st crack). Although the bean looks good on the outside I believe what is happening is the internal bean temperature never gets hot enough due to too much external heat. For me this means my coffee (even dark roasts) don't brew as dark as I'd expect and the flavor is subtle instead of bold and coffee-like.

    Check out "Roaster school online" by Mill city roasters on YT probably WAY to much info but it does a good job of explaining what is going on with the bean.


    2 years ago

    Try McMasters and Carr (Internet) for small mesh wire cloth. Call them and a rep will answer your questions as to screen openings sizes. A 1/8inch mesh size will contain any coffee bean.

    Nice. I've got a nice little fire bowl, so i'm going to have to try this over that :D

    Just need to make a roaster :)

    1 reply

    Great! Please share what you come up with here :-)

    Figuring out how to make this roaster took some doing. Hopefully, if you follow the steps here, you'll be roasting in no time! I could churn out a new one in an hour or so now if I had all the parts on hand.


    1 reply

    Hi Vlad, I completely understand. I think this project is doable with traditional woodworking tools. You could get handy with a router and do something fairly similar - the groove for the steel rod is the most important part and that's a straight line.

    If you do end up making your own without a CNC, please share what you come up with!

    This is a great idea. Have you thought about using different types of charcoal like lump, mesquite or even different types of wood chips.As for heat distribution maybe make a rectangular steel box at Tech Shop. Ooh, Ooh and then hook up a small motor. I wish I had a tech shop near me.

    2 replies

    I second the use of a motor, perhaps even set it up with an arduino so that you can spin it at different speeds for different time periods, like really fast for 20 seconds then slow for 5 mins. Just a thought

    We do use different types of charcoal. Friends have suggested smoking tobacco leaves in the grill to give the beans a different aroma. All good things to try! I like the idea of the rectangular box to sit under the roaster to control the heat, too.

    As for the motor, this would certainly make the process more automatic and might be exactly what some want out of this. We've found it really relaxing to turn the beans with the little crank and we usually do this in a backyard with a group of friends, so there are different 'jobs' that we rotate around between batches and everyone seems to enjoy being hands-on, so I probably won't add a motor to ours. There are some other notes - the roaster is fixed with a lock nut on one end cap, but the other end cap floats to add and remove beans, but while the roaster is spinning different things can happen and with a person actively spinning you get instant feedback if something feels odd instead of accidentally letting a batch burn. That likely points to other things that can be improved if we wanted to invest more time into it.

    Very cool idea. I do hope you're using stainless steel and not galvanized steel: the zinc/zinc oxide fumes from galvanized will get into your freshly roasted coffee and could cause you health problems over time.

    1 reply

    Good note - I should have mentioned being careful about food safe materials in the instructable. In addition to stainless steel, you should watch that the wooden spacer is solid wood or "E0" grade plywood as some plywood uses formaldehyde based resins or glues, which is also not great to have near coffee beans.

    Thanks! Let me know if you have a go at your own roaster and if you think of any improvements.

    I love coffee and that includes making it myself and roasting it good job man good job

    1 reply

    Thanks! I love the ritual of drinking coffee and now that ritual includes knowing about where the beans come from and roasting them with friends. Didn't seem useful as part of the instructable, but we make an afternoon of roasting with good friends and food in the backyard. It's been a lot of fun.