The Fresh Loaf

A Community of Amateur Bakers and Artisan Bread Enthusiasts.

WFO coffee roaster

dsoleil's picture

WFO coffee roaster

I just had to share my latest WFO development.  I designed a coffee bean roaster for the oven.  While I'm waiting for the coals to cool off a bit to bake my breads, I started roasting coffee.  I used two stainless steel colanders from Target, some hose clamps and stainless steel wire.  So, for those who want to add coffee to your breads, this was a fun way to use the oven.


Roo's picture

I am in the process of building ours, and hve wondered about roasting coffee in the oven and how to do it. 

Can you share the process with us?  What type of beans, how long it took ect?

tomsbread's picture

How long did it take to get to the second crack? Got to try this in my beehive oven someday. I have not been able to get an even roast on my wok and the smoke is killing me when I do it in my kitchen. The steel colander is a great idea to jiggle the beans as they roast.


asicign's picture

I'm about to embark on the construction of a WFO, so this  thread is of interest.  I also roast my coffee beans, using the 'HDDB' (Heat Gun Dog Bowl) method. Roasting is a pretty tricky business, because the beans need constant movement to ensure even exposure.  Timing is critical: the beans in the photo look overdone to me, but that's a matter of personal preference.  I don't know if you could hear the beans if the oven were closed, and getting rotation of the roasting container would be a challenge.

SylviaH's picture

Great invention for roasting your coffee beans...thanks for sharing!


dsoleil's picture

Wow. Great questions.  Fun to find other roaster/bakers on TFL.  Let me see if I can address all the questions...

First, I get all my green coffee beans from Sweet Maria's.  They also have a ton of information on how to roast.  Kinda like the TFL of coffee roasting.  The roast pictured looks dark because it is an espresso roast and is great anywhere from a full city+ to vienna roast.  I did this one first because I knew I would probably over-roast the first time out.  I read that generally you want somewhere between 400-500 degrees of heat for roasting.  

A few of the reasons I wanted to roast in my WFO are:

1.  When the oven is hot, the heat is reflected from all directions giving the possibility of a more even roast.

2.  The oven stays hot with the door off.  This is the big problem with roasting in your kitchen oven.  It doesn't retain any heat if the door is open.  In a WFO, the you can roast with heat coming from all directions AND the door open.

The trick then was to design something that could rotate and keep the beans moving.  I admit this was little more than chewing gum and duct tape, but it worked surprisingly well.  

Here is a detail picture of the attachment point:

These are two 8" stainless steel colanders from Target.  Two hose clamps.  One three foot dowel rod and some stainless steel wire.  Total cost was around $20.

It took me about 5 minutes to roast the beans but it should have taken more like 10.  My oven was a bit too hot, but a little more practice should fix that.

With this design, I can turn the handle and the colanders will rotate around the handle axis giving the effect of a drum roaster.  Keep those beans moving!  I generally went back and forth, left to right and back to left.  Doing a 360 with the colander is a little clumsy.  However, to my surprise, you can also toss the beans like they are in a pan too.

When you want to check your roast, you can pull the thing out quickly and get a good view of the color through the metal mesh.  You can then stick it back in for longer or if the roast is done, you can stop it very quickly by tossing or rotating the beans in the cool air outside the oven.  

Can you hear 1st and 2nd crack?  Yes.  My recommendation though is to make sure your fire has burned down to coals or you have removed the coals.  Fire wood snapping sounds very similar to 1st or 2nd crack.  You want to eliminate any confusion.  

There are a few disadvantages to this design.  First, I used a wood dowel rod which is starting to char.  I will eventually need to replace that with a metal pole or another wood pole.  Second, when the colanders are cinched tight to the pole, it slightly warps the flat top of each colander meaning that they don't fit perfectly together leaving just enough space for small beans to fall out.  That's why I used a few inches of stainless steel wire like a twist-tie to close the gap on either side and one on the colander handles.  It is inconvenient to work with metal wire to keep the thing perfectly shut.  But for the 1st generation design, I'll take it.   

I too stopped roasting in my house because of the smoke.  Now that it is all outside, it is a real pleasure to roast again.  

I roasted four different kinds of coffees yesterday (all decafs) and was very happy to see that there was no scorching of the beans.  The roast turned out very even in all the batches.  

Feel free to ask more questions or even make suggestions if you have them.  Designing this contraption took a lot of people's ideas, even the old guy at the hardware store!



SylviaH's picture

might help them from catching fire or burning up so fast.  Sometimes I poke my wfo coals around with a wooden stick instead of my metal wfo utensils..If I soak them in a little water first it helps to keep them from catching fire.  Metal is best won't shrink.  You have a great start and soon I bet you have the whole thingy perfect. 


Mini Oven's picture
Mini Oven

and the feet from the colanders and roll it around like a ball in the oven?

Minnow trap?  (They probably stopped making them out of metal years ago!)


audra36274's picture

  But the minnows keep getting to much of a buzz from the coffee and won't stay on the hook !

dsoleil's picture

Yes, water soaking the pole is a good idea.  I will have to try that.  

As for the feet and handles on the colanders, these colanders didn't have feet but rather a round ring to serve as a foot.  The handles don't detach because the handles extend to become the top frame of the colander that holds the mesh.  Although rolling would be a fun experiment in a colder oven.

I do have a laser thermometer.  Because this was the maiden voyage, I was more concerned about my design than the temp in the oven.  The roast was definitely too fast but still produced a quality cup.  Sweet Marias has such great beans.  They are hard to mess up too badly.  I'm guessing the oven was 500+ and pushing 600 degrees.  Much too hot.  I had just finished pizzas and was down to small glowing coals.  This is also the first time I've cooked anything above the cooking surface, so there's that X factor too in getting a half-way accurate temp.  

Next time, I plan to shoot for the low 400s in temp and try to get a more typical 10 minute roast.  My first roast I completely missed the first crack!  Skipped it and went straight to second crack.  I guess that's how we learn...




dsoleil's picture

Just thought I'd share my latest progress.  The wood pole has been replaced with metal conduit... the long hard metal piping that usually holds electrical wire.  I cut a piece down to 6' long.  Interestingly, only the part that goes in the oven gets hot.  The heat does not travel down the pole.  I'm planning to add "grip tape" to the bottom of the pole for easier handling.  

I also figured out that the best heat for my oven to roast coffee is VERY low coals.  You know, the tiny glowing embers, maybe no more than an inch long.  More than that roasts too fast and just ambient heat from an empty oven is too slow.  Very low coals gives me a roast in 8-10 minutes.  I'll get some temps for you next time.  

More next time.  Happy roasting and baking!


dsoleil's picture

Hey All,

My coffee roasting is getting better every roast.  I found a technique that seems to be a winner.  I roast when my oven is between 600 and 700 degrees F.  I also keep a heap of hot coals in the back of the oven now rather than roasting over low coals.  The difference between the heat next to the coals and the heat near the door can be close to 200 degrees.  It gives you a great deal more control over your roast.  If you want more heat on the beans, push your pole in further.  If you want less heat, pull your roaster out closer to the doorway.  I get very distinct 1st and 2nd crack now with a roast taking from about 7-10 minutes.

You can also throw more wood on the coals if the oven cools down too much.  

With this technique, I produced my first 5-star coffee roast (in my opinion).  I can count on one hand the number of coffees I have rated 5-stars in my roasting experience going back about 7 years.  

Give it a go.  We're now drinking great coffees roasted in the WFO.