How might I roast coffee at home without investing in an expensive roasting machine?

Hot Air Popper

The cheapest and simplest is to use a (cheap) electric hot air popper. The old favorite is the West Bend Poppery, but you can use anything as long as the vent holes (where the hot air comes in) are on the sides rather than the bottom.

I've roasted a lot of coffee this way. It works, but there are a few downsides. The biggest problems:

• The circuation is designed for popcorn, which expands a lot more than roasted coffee beans. I've needed to stir the beans manually in order to get an even roast. They don't have to be stirred constantly, but you can't just drop the beans in and walk away.
• The capacity is pretty low, especially when you take the circulation into account. I can only roast a half a cup at a time, which is pretty slow.
• The temperature doesn't get quite high enough to really bring the flavors out. The roast is good, but it's really mellow.

[source: Chris g Collision, Flickr Creative Commons]

I've read about modifications you can make that will improve these: changing out resistors, modifying the airflow, and even hooking up an Arduino to control the heat a lot more closely, but it seems like more work than I've wanted to invest in the process.

Heat gun / metal dog bowl method

My brother's moved on to this approach, and I'm soon to follow. The benefit of a heat gun is that the temperature is high enough to get a good roast, and the airflow is high enough that you can roast a few cups of coffee at a time.

[source: Ocell, Flickr Creative Commons]

More Insanity Sweet Maria's sells green coffee beans, and lists a huge amount of home roasting methods, including Weber Kettle conversions. The sky's the limit, but I'd start small with the air popper or the heat gun first.

I'd do this outside Some methods have you roasting the coffee in your kitchen - in the oven, on the stove, etc. I wouldn't want to do this myself, for two reasons. The beans have thin husks on them, which come off as the beans are roasted. They're messy, and I wouldn't want them flying around my kitchen. Also, roasting coffee doesn't smell as good as you'd think it would.

Sources of more info:

• http://www.ineedcoffee.com/section/roasting/
• http://www.sweetmarias.com/articles.php#roastAndBrew
• http://www.sweetmarias.com/homemade-homeroasters.php

You could use a drill and soup can.

http://lifehacker.com/5494207/roast-coffee-with-a-drill-and-a-soup-can
_{(source: gawkerassets.com)}

Other life hacker tips for roasting coffee at home on the cheap

http://lifehacker.com/226925/diy-coffee-roasting

http://lifehacker.com/365235/roll-your-own-coffee-roaster-on+the+cheap

I just use in any pan. Put in a single layer of beans (don't overcrowd them) and heat it to medium heat. Keep shaking the pan from time to time, so the beans turn and will be roasted from all sides.

After a few (3 or 4) minutes you will hear the beans starting to "crack". At this point, they will be lightly roasted. You could stop now or keep going, if you like a darker roast. The cracking will stop and the beans will stay quit for a few more minutes.

Then the beans will crack a second time. At this point, they will be medium roasted. If you want them darker, just keep going. I usually stop just after the second crack. But you can stop at any time after the first crack. You just have to keep experimenting how dark you like your roast.

I roast 'em in a basic cast iron skillet, but really anything will do. You can put 'em in the toaster on a pan, you can put 'em on a baking sheet in the oven. Give 'em a good shake every now and then so they don't only toast on one side, and don't set the temperature so hot that they burn.

They sell these pans with holes for air circulation, if you're a hard core oven roasting person. I don't much care for doing it in the oven myself because they tend to get more done on one side. Some people like the taste that results though, so you can try it. Lot of people will tell you to put your oven up to 500+ degrees (!!) but 500 is really about as hot as you'd ever want your beans. Roast them at that temp for 15-20 minutes.

I've heard that you can roast them in a hot air popcorn maker. You need to listen for the 'crack' to know when they are done I believe. I'll look for a reference...

EDIT: found one

It is ridiculously easy to roast coffee beans that will produce delicious coffee. Fresher than anything you can buy in a store (even Starbucks). A paritcular model of hot air popcorn maker, the Westbend Poppery, is considered by many to be the best for roasting coffee. It's not made any more but you can find it on eBay. Be sure it's the Poppery and NOT the Poppery II. The latter uses fewer watts and doesn't roast beans as well. There are many good YouTube videos showing how to roast this way. Definitely do it on a porch or terrace because roasting coffee makes smoke and the beans' hulls (chaff) go all over the place.I started roasting this way and then got a home coffee roaster (the Behmor 1600) that makes superb roasted beans. Be bold and do it!

My brother-in-law brought home some fresh coffee beans from Ethiopia and roasted them with a heat gun.

Good step-by-step here.

Find an iRoast 2. This is very similar to a pop corn popper but is purpose built. So larger roasting volume, ability to create and store profiles, chaff collector, connector to attach piping to pipe fumes outside etc.

If you are in an apartment, a fluid bed roaster is probably your only real choice. Other roasting methods can generate a massive amount of smoke.

A fluid bed probably generates smoke too, but the relatively high speed fan (to circulate the beans) dissipates it quite quickly. You probably want to get some concertina tubing and pipe the smoke outside anyway though.

I use the popcorn popper as noted by other answers and get good and consistent results. However, I've always wanted to try the Corretto method (search for posts on Coffee Snobs) which involves a bread maker, heat gun, a fan and maybe a fire extinguisher...

Contrary to what the other answers are suggesting, I think it is a bad idea to home roast your coffee. Generally speaking, the single most important factor behind how your coffee tastes is the "freshness" of your coffee beans. i.e. you need to (a) use coffee that has been roasted very recently, ideally in the last few days, and (b) grind the coffee just before you brew it.

Further, roasting a coffee is not a perfect science. And its best left to professionals (its kind of like blending different wines..). You are far better off trying to find a local store (or on-line supplier) who has a supply of fresh-roasted beans.

Corby Kummer, author of the widely respected "Joy of Coffee", agrees with me.

Another article on building your own home (small batch) coffee bean roaster: this uses a propane burner and screwdriver-powered boil of stainless-steel screen.