Roasting coffee in an unmodified bread machine is about as easy as it gets. I've demonstrated it to a number of people, many of them folks who have never roasted coffee at all, and they all seem to catch on quickly. People who learn about it over the web have been contacting me with questions, so I thought I'd write up a little FAQ that answers the most common questions.
As the conversations about this method of roasting develop, this FAQ is changing, so check back from time to time.
WARNING: BREAD MACHINES AND HEAT GUNS WERE NEVER DESIGNED TO ROAST COFFEE. YOU ARE USING AN ENORMOUS AMOUNT OF HEAT AND APPLYING IT TO A SUBSTANCE THAT CAN, AND WILL, CATCH ON FIRE IF YOU ARE CARELESS. IF DONE CAREFULLY, AND WITH YOUR FULL ATTENTION, IT SHOULD BE SAFE, BUT DO NOT DO THIS IF YOUR MIND TENDS TO WANDER OR IF YOU ARE JUST PLAIN STUPID.
THIS CAN BE RISKY, AND THE RISK IS ALL YOURS. IF YOU BURN DOWN YOUR HOUSE, IT IS YOUR OWN DAMN FAULT. IF YOU DECIDE TO TRY THIS, PLEASE UNDERSTAND THAT WE WILL TAKE NO RESPONSIBILITY AT ALL FOR ANYTHING ROTTEN THAT HAPPENS TO YOU, YOUR PROPERTY, OR ANYONE ELSE.
What equipment do you need to roast coffee in an unmodified bread machine?
You will need a bread machine, a heat gun, a fan or other cooling device, a pot-holder or heat resistant mitt for lifting the bread pan out of the bread machine housing, a colander or wire basket in which to dump the beans, and a fire extinguisher (just in case).
This is an outdoor activity. Roasting coffee produces lots of smoke and lots of blowing (and sometimes glowing) chaff. Do not do this indoors.
Can any bread maker be used to roast coffee?
There are a few things you want to watch for when choosing a bread machine to use as a coffee roaster. You want an all metal stirring assembly and you want the bottom of the pan to be solid. Some bread machines have plastic pieces holding the stirring thing-a-ma-bob in place, and the heat gun could melt the plastic. Do not use any bread machine that has a plastic stirring assembly or if the receptacle in which the pan sits is plastic, rather than metal. In some machines, the bottom has a hole in it, and coffee beans will fall out when you lift the pan to dump the beans for cooling. Not good.
I understand that some bread machines have Teflon coated bread pans. It is probably wise to avoid those as the off-gassing of Teflon in high heat conditions is a health hazard. Watch for Teflon stirrers/paddles as well. You can remove Teflon with a solvent or by sorta sandblasting it, but it's apparently not all that easy. My machine once had Teflon on the paddle, but it has disappeared.
As more folks try this, it is also clear that some bread machines have thermostats that turn the whole machine off when the bread pan gets really hot. You can either reach into the guts and disconnect the thermostat, or head back to the thrift store and try another machine. It seems that at least for some of the bread machines with thermostats, the sensor itself can be seen in the housing of the bread machine, in the inner wall. When shopping the thrift stores, it is better if you can find one without a thermostat, so pull the pan and look to see if you have a sensor embedded in there.
My friend Carole, from the Sweet Maria Home Roast List has provided pictures and a narrative explaining how she got the thermostat out of the way on her Panasonic 2 pound bread machine. It won't be exactly the same for every bread machine, but this may help you if you need to work on your own machine.
I use a Sunbeam 5891. It's cheap and does not need any sort of modification.
How big/deep does the pan have to be?
In part it depends on the size of the roast. My bread machine is designed for a two pound loaf of bread. It doesn't make a horizontal loaf, so the pan is deep enough for two or more pounds of beans, even after they have expanded.
How much should you roast at a time?
I don't know that there is a should, but even though I found I can roast almost a kilo (2.2 pounds), my roasts seem to come out better if I stay below 1.5 pounds. I've never roasted less than 3/4 of a pound in it, and my "normal" batch these days weighs a bit over a pound.
What cycle do you use to roast coffee?
You use the dough cycle. All bread machines seem to have one. And if your machine is designed to produce a 2 pound loaf of bread, there should be more than enough time on the dough cycle to roast your coffee. If you use a bread machine with a short dough cycle (fewer than 20 minutes or so), try stopping the machine at 5 or 6 minutes, well before first crack, for a few seconds. The cycle should reset, and then you can start again. My experience has been that you can not immediately start again if you let the machine complete the cycle. It could be a real problem to wait for a few minutes at that point in the roast.
You will NOT be using any of the cycles that bake bread. All of the heat comes from the heat gun.
What kind of heat gun is best?
You want a heat gun with at least two settings, a high and a low. The high should be in the neighbourhood of 1500 watts. You will use that setting to get the beans up to, and part way through, 1st crack. The lower setting is useful when if you want to prolong the time between 1st and 2nd. I paid $34 CAD for my heat gun. I think it's just plain silly to spend big bucks on one, unless you are planning on using it to strip paint off wood, too. The cheaper heat guns weigh less, and that is an advantage as it keeps you from getting tired as you wave it around the bread pan.
Note: After about 120 roasts, my heat gun died. The fan gave out. It came with a three year guarantee, so it has been sent to the Heat Gun Abuse Judgement Board to see if it only qualifies for repair or if it will be replaced. Whilst waiting, I bought a new one. I decided to go with the same Mastercraft model, but this year it only came as part of a kit with a case and various tools and cost me $54 Canadian. These are the specs:
I immediately noticed that with the new gun, I could keep the nozzle further from the beans and still get the same roasting times. I assume that means that it loses some oomph as it ages. I wonder what the Mastercraft people (assuming they actually look at it) will think of all the chaff in my heat gun? One person I know puts some nylon hosiery over the air intake to keep the chaff from entering the heat gun innards. I haven't tried that.
I brush chaff away from the air intake vents as I roast, but it still collects in there. The housing for the heat gun is held on with four screws. Taking it apart and cleaning out the chaff periodically is probably a good idea.
How far away from the beans do you hold the heat gun?
The distance between the business end of the heat gun and the coffee beans controls the speed of your roast. If you are too close, you risk scorching the beans on the outside whilst the inside of the beans stay "green". If you have the gun too far from the beans, you risk baking them and stalling the roast. I've found that maintaining whatever distance seems to get one to 1st crack somewhere between 8 and 10 minutes on the high setting works well. I maintain that distance throughout the roast, but that means moving the heat gun *higher* as the beans expand.
Can you use something to hold the heat gun in place, or do you have to keep it moving?
You can keep the heat gun in one place, but I'm not convinced it's a good idea to do it. You can use some sort of grippy vice like thing, a stand meant to hold a hair dryer, or even an upright chicken roaster, perched over the bread machine pan. I'm not at all sure it's good for the pan to have all that heat applied to one spot. You also risk having beans hit a metal surface that is just hot enough to produce some scorching. And remember, as the roasting beans increase in volume, you will want to adjust the distance between the end of the heat gun and the bean mass.
How adjustable is all of this, can you profile?
It is very adjustable. And yes, you can profile. In fact, you can even drill a hole though the bread machine housing and into the pan, through which you can place a thermocouple or some other thermometer like device. I don't do it, but you can. Of course then it's not really an unmodified bread machine, right? You can vary the heat gun settings and the distance from the beans. With practice, those two things alone will allow you to control your time to 1st crack, how quickly 1st crack ends, and your time between 1st and 2nd.
Can you give an example of a more or less typical roast?
Begin the roast with the heat gun on high. Your bread machine might begin the dough cycle stirring fairly slowly for a minute or two. Don't worry, it's fast enough. It also may pause every 30 seconds for a brief time. Not to worry, that's fine, too.
Move the heat gun around the inside edge of the bread pan. You don't have to go quickly; just keep it moving.
You should notice some colour change and some bready smells about 2-3 minutes in and you should have some definite tanning by 4-5 minutes. Chances are, you will then hear the tentative beginnings of 1st crack at about 8 minutes+. Don't forget to move the heat gun as the beans expand.
When 1st crack is really tooling along, about 9-10 minutes into the roast, decrease the heat to the lower setting. If 1st crack peters out, but you are pretty sure you still have beans that "should" pop, but haven't, increase the heat again. You don't want to stall the roast.
You can stop the roast, and dump the beans to cool, any time after 1st ends.
Depending on how long you think you should have between the completion of 1st and the beginning of 2nd, you may want to increase the heat again about a30 seconds to a minute before you want 2nd to begin. Keep it there until you end the roast, but be sure that you do not have the heat gun so close that you risk setting everything on fire. Remember, you can pull the heat gun further from the bean mass, you can go back to the lower setting, and you can turn the heat gun off and aim a fire extinguisher at the beans. Pay attention, you could get yourself in big trouble if the beans decide to mimic a wild fire.
Can you roast in cold weather?
Yes, you can. If you keep your bread machine outdoors, you will have to warm it up if the temperature goes below freezing. I do this by aiming the heat gun at the empty bread pan, whilst it is in place in the bread machine housing. it only takes a minute, and I have roasted at -20C. My heat gun seems to fire-up at any temperature, but yours may not, in which case, keep it indoors until you are ready to go. I store my bread machine and heat gun in our unheated garage. I have also roasted in the garage, with the garage door open. It's messy and the garage stays smoky for a fair amount of time.
How do you cool the roast?
When the roast is done, you will want to cool the beans in under two minutes. Until the temp comes down, the beans will continue to roast. I dump the bans into a wire basket, and place the basket over a strong fan, with the air going up. This blows the chaff out, and cools the beans quickly. I shake the basket over the fan. Within 30 seconds or so, the beans are cool enough so that I can stir them by hand.