Beyond getting my first fairly decent espresso machine (a Krups Novo Compact), my first real introduction into how good coffee could be has to be the day I discovered I could home roast with nothing more than green coffee, a hot air popcorn popper, and a metal colander.
Tools Needed for Home Roasting
The tools required for home roasting are those that won’t break the bank, even if you go all out. At the very minimum, you need the following:
Hot Air Popcorn Popper. While there’s some debate on this, it’s preferable if you get a model that has side vents inside the machine, at the base of the interior funnel. Some models have a grate on the bottom, and are generally not recommended.
Mesh colander One big one should suit, but two are better. You need these to cool down your beans as quick as possible – tossing the sizzling hot beans from one to the other is how you do it. Alternatively, you can use an extra large cookie baking sheet – the large surface area will quickly “leech” away excess heat from the beans.
Large Bowl: really, any bowl will do; but it has to be big. You place the bowl in front of the popcorn popper’s air chute to collect all the chaff that will blow off your coffee as it is roasting.
Oven Mitts: to handle the hot popper as soon as you unplug it and want to remove the top and dump the beans out into your colander or cookie sheet.
Green Coffee: These days, there’s dozens of sources online for amazing quality green coffee.
Popcorn Popper
Colander
Chaff Bowl
Oven Mitts
Before You Begin Roasting
I can’t stress enough that this how to is a “do at your own risk” type instructional. Using a popcorn popper to roast coffee definitely voids the product’s warranty. Also, most current-day popper will burn out within 4-6 months of roasting coffee, because of the maximum stresses put on the machines – way beyond what they normally do for popcorn.
Home roasting is also extremely hands on. You must never leave the popcorn popper while it is roasting coffee. At temperatures as high as 475F, things can spontaneously combust and catch fire. It rarely happens, so you shouldn’t worry too much about this, and I’ve never heard of anyone setting their kitchen on fire while actually paying attention to the roasting process. Fires have happened, but in almost every case I’ve read about, it was through negligence – the home roaster left their appliance alone, and the coffee was roasted beyond a dark roast, and eventually ignited. While the danger is almost non-existent if you’re hands on, having a fire extinguisher or bucket of water nearby, or roasting out doors is definitely recommended. IF you do see a fire start inside the popper, unplug it and douse it with the fire extinguisher or water.
Oh and the chaff. It’s going to get everywhere!
With the scary stuff out of the way, you also need to know the following:
- Roasting in a popcorn popper typically takes about 5-7 minutes for a light roast, 7-8 minutes for a darker roast.
- Most popcorn poppers on the market today roast about 75-85 grams of green coffee per batch – or enough coffee for a 10 cup pot. You can usually do 2 or 3 back to back roasts, but this will shorten the popper’s life.
- Your ears and eyes and nose will tell you how your roast is progressing. It’s not something that we can really fully train you on in this how to – it comes with experience. You’ll soon be able to distinguish between first and second crack (explained below), and the different smells during the roast.
- Even with the dire warnings above, home roasting is very safe – I’ve roasted at least 1,000 or more batches in popcorn poppers over the last 10 years, and have never had anything beyond a slowly melting plastic lid.
- Coffee loses up to 20% of its weight during roasting (and also increases in physical size by about 30-40%). So 85 grams of green can deliver as little as 70 or less grams roasted.
- Coffee needs to rest 2-5 days after roasting, as it degases. But you’re welcome to try the coffee right after roasting, a day after, and two days after, if for no other reason to discover how coffee matures, peaks, and then declines after its roast date.
- And one more caveat – I’ve read that the some recent models of popcorn poppers now have a heater cutoff fuse that will shut down the heating coils once the temperatures get above 400F. I’ve not experienced this myself, but if you buy a popcorn popper and it can’t seem to roast past first crack, this may be the reason why. Caveat emptor.
Popcorn Popper Roasting Step by Step
01 85g of Coffee
02 Pouring the Beans
03 Stirring Early On
04 Chaff Collecting
05 First Crack
06 Temperatures
07 Second Crack
08 Dumping the Beans
09 Sifting the Beans
Optional Tools
The above is really all you need to roast coffee at home; that said, here’s some optional choices to make the roasting job more educational, less seasonal, and more consistent.
Digital Scale: Popcorn poppers typically roast about 75-85 grams of green coffee – roughly enough to produce a 10 cup pot of coffee – though some can roast more, others roast less. A digital scale helps you be more accurate in not only doing consistent roasts, but also finding out what the ideal green bean starting weight you need is.
Candy Thermometer: Most of the needle thermometers you see out there are designed for baking and meats, and measure up to around 220, 250F, but there is a special type of needle thermometer that can measure up to 550F or higher (but costs about the same as the other meat thermometers – around $10-$15). You need the higher temperature one to measure your roasts, which can get as high as 475F.
Big Brown Box: If you want to roast outdoors and live in a colder climate, get a box big enough to fit both the popper and your big bowl for the chaff in. Even in temperatures as low as 0 Celsius, the box acts enough as an insulator to keep the area around the popper warm so it doesn’t screw up your roasting times. Poppers do not like cold weather. Just don’t burn everything down.
You can use the thermometer in several different ways. Many people literally drill an angled hole in the side of their poppers so that the needle sits right in the middle of the rotating coffee, and can easily be read while the roast goes on. You can also drill a hole in the plastic lid of the popper, but I’ve found the thermometer gets so hot there, it slowly melts the plastic, deforming it.
Use the thermometer to chart things like at what temperatures 1rst and second crack occur, when you want to stop the roast, etc etc.
Lastly, if you want to modify your popper like I’ve done for this how to, here’s what you need.
Candy Thermometer
Drill Time
Therm in Place
Needle Placement
This how to was originally written in 2006, and updated in 2012. We consider it a retired how to, but is presented for your information.
