Revised: September 27, 2015
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About Coffee: Home Coffee Roasting

Quick Guide to Home Roasting

Outlined below are instructions for two home roasting methods:
  • Using a Hot-Air Corn Popper
  • Using a Gas Oven
Kenneth Davids covers other home coffee roasting methods in his book, Home Coffee Roasting: Romance & Revival including: Stove-Top Roasting with a Crank-Type Corn Popper; Roasting in a Convection Oven; and Roasting in ovens Combining Conventional and Convection Functions.

Roasting with Recommended Designs of Hot-Air Corn Popper

  • Somewhat simpler than other methods. Roasting temperature, for example, is already established.
  • Produces more consistent and uniform roast than other methods.

  • Only units with recommended popping chamber design should be used to roast coffee. Other designs are potentially dangerous when employed for that purpose.
  • Roasts considerably less coffee per session than stove-top and oven methods.
  • Roasting smoke tends to be more difficult to control and vent than with oven methods.
  • Regular use to achieve very dark roasts (black-brown and shiny with oil, common names Italian or dark French) will shorten life of popper. However, can be used to produce moderately-dark to dark roasts usually called French or espresso.

Taste Notes

Hot-air poppers roast relatively quickly, thereby emphasizing bright, acidy notes in medium roasts and pungency in dark roasts. Taste tends to be clean and straightforward compared to more complex taste of beans roasted in gas oven or stove-top corn popper.

What You Need
  • Hot-air popper of recommended design only. Other designs may be dangerous when used to roast coffee.
  • Large bowl to collect chaff.
  • Sample beans roasted to style you prefer.
  • Green beans (same volume per session as volume of popping corn recommended by manufacturer of popper, usually about 4 fluid ounces or 1/2 cup).
  • Colander for cooling, large enough to accommodate about twice volume of green beans you intend to roast.
  • 2 oven mitts or pot holders.

  • Position popper under kitchen exhaust fan or near open window to dissipate roasting smoke. Can by positioned out-of-doors, but only in clement weather; low ambient temperatures (under 50F) may prevent coffee from roasting properly.
  • Place in popping chamber same volume of green beans as volume of popping corn recommended in instructions accompanying popper. Do not exceed this volume.
  • Make certain plastic chute (hood-like component above popping chamber) and butter cup are in place. Do not operate without chute and butter cup; they assist in maintaining proper temperature in popping/roasting chamber.
  • Place large bowl under chute opening to catch chaff.
  • Place sample roasted beans where they can be easily seen for color comparison to beans inside popper. Make certain cooling colander and oven mitts are at hand. If you wish to accelerate cooling of beans by water-quenching have pump spray bottle ready.
  • Plug in or turn on popper.
  • In approximately 3-4 minutes dark, coffee-smelling smoke will appear and beans will begin to crackle. Turn on kitchen exhaust fan if indoors.
  • About 1 minute (for light to medium roasts) to 3 minutes (for moderately dark to dark roasts) after smoke appears and crackling sets in, begin checking color of beans by lifting out butter cup with oven mitt and peeking into popping chamber.
  • Continue checking color of roasting beans against color of sample beans at 30-second to 1-minute intervals.
  • Roast develops relatively quickly with hot air poppers: typically 5-6 minutes to medium roast, 7-8 minutes to medium-dark, 9 to dark.
  • When roasting beans are same or slightly lighter color than sample beans unplug or turn off popper and using oven mitts, immediately lift popper and pour beans out of popping chamber through chute opening into cooling colander.
  • Carry colander outside or place under kitchen exhaust fan and stir or toss beans until warm to touch. To accelerate cooling, water-quench.

Problems and Refinements

Hot-air poppers can be easily fitted with metal candy thermometers to monitor approximate inner temperature of roasting beans. This modification permits the use approximate internal temperature of beans to determine when to conclude roasting session. Kenneth Davids outlines this process in his book, Home Coffee Roasting: Romance & Revival.

Getting Out the Chaff

Removing the chaff using the hot air popper is no problem because the moving air removes the chaff during the roasting process. In other methods, tossing or stirring the beans in a large colander facilitates cooling, and rids the beans of most of their chaff. Any amount that is left in the beans will have little to no effect on flavor. The single most important piece of advice to home roasters in regard to chaff is not to be obsessive about it.

Roasting in a Gas Oven

  • Temperature in roasting chamber (i.e. oven) is easily controlled and repeatable.
  • With most gas ovens roasting smoke is effectively vented.
  • More coffee can be roasted in given session than with other methods.
  • Control over temperature enables those who experiment to roughly compensate for differences in density of green beans and broadly influence taste of roast.

  • Hot spots inside some ovens and lack of strong convection currents may cause beans to roast unevenly: some beans lighter, some darker, some between. Solutions to this problem may require patience and experiment.
  • Timing roast can be difficult because color of beans may not be uniform and beans may be difficult to see inside oven.
  • Precision in roast style may be difficult to attain owing to uneven roasting.

Taste Notes

Somewhat uneven roast brings out complexity and depth of taste, since a range of roast styles may be present simultaneously in any given sample of beans. Gas-oven roasting probably produces best results for those who like medium-dark (full-city) through moderately dark (espresso) styles. It probably should be avoided by those who prefer either light or very dark roasts.

What You Need
  • Ordinary kitchen gas oven. (Do not attempt to use microwave ovens for coffee roasting. Conventional electric kitchen ovens can be used following these instructions, but typically produce roasts too uneven for most tastes.
  • One or more flat, perforated pans with raised edges. Palani Plantation produces inexpensive foil pans especially designed for oven coffee roasting. Some baking pans designed to crisp bottom crusts of breads or pizzas also work well. Perforations should be relatively close together (no more than 1/8" apart) and small enough to prevent coffee beans from falling through (maximum about 3/16" diameter). Pan should have raised lip around edges.
  • Sample beans roasted to style you prefer.
  • Enough green beans to uniformly cover surface of baking pan(s) 1 bean deep.
  • Colander for cooling, large enough to accommodate about twice volume of green beans you intend to roast.
  • 2 oven mitts or pot holders.
  • Flashlight (necessary only if interior of oven is not illuminated and remains dark when you peer through window or crack open door).

  • Virtually all gas ovens will produce a reasonably consistent and very flavorful roast, but success may require patience and experiment. If your first roast emerges uneven in color, don't give up.
  • For Palani Plantation pan: Follow instructions accompanying pan. Preheat oven to 425F to 450F. For brighter, more acidy taste in medium roasts and more pungency in dark roasts try upper range of temperature; for more body and less acidity/pungency use lower end of range.
  • Preheat oven to 500F/260C to 540F/280C depending on condition of green coffee and desired taste characteristics. For brighter, more acidy taste in medium roasts and more pungency in dark roasts try upper range of temperature; for more body and less acidity/pungency use lower end of range.
  • Spread green beans closely together, one bean deep (no deeper) across entire perforated surface of baking pan. Pat beans down with flattened hand until they are densely but evenly distributed, touching or almost touching, but not piled atop one another. Make certain all of pan is covered with single layer of beans.
  • Place baking pan charged with beans on middle shelf of preheated oven.
  • Place sample roasted beans where they can be easily seen for color comparison to beans inside oven. Make certain cooling colander and oven mitts are at hand. If you wish to accelerate cooling of beans by water-quenching have pump spray bottle ready.
  • In about 7 to 10 minutes you should hear crackling from inside oven and smell coffee-like scent of roasting smoke.
  • About 2 minutes after crackling begins (for lighter roasts) to 3 minutes after crackling begins (for darker roasts) peek inside oven, with flashlight if necessary. If oven has no window, crack open oven door only as long as it takes to compare color of beans inside oven to sample of roasted beans.
  • Continue peeking at about 1 minute intervals, making comparison to sample beans. When average color of roasting beans is approximately same as sample, pull baking pans out of oven using oven mitts and dump beans into colander.
  • Over sink or out-of-doors, stir or toss beans in colander until cool enough to touch and until most loose roasting chaff has floated free. To accelerate cooling, water-quench.

Problems and Refinements
  • Actual temperatures in ovens may differ from control settings. Compare the actual temperature as indicated by an oven thermometer to control settings before first roasting session. Compensate for any difference when setting temperatures thereafter.
  • Beans always will roast somewhat unevenly. Nevertheless, they may taste as good as or better than uniformly roasted beans. Try them. If you don't like flavor complexity, or if range between dark and light beans is too great (if darkest beans are almost black and lightest beans medium-brown, for example), one or more of following adjustments may be needed:
  • Make certain beans are uniformly spread one bean deep but no more over entire surface of pan.
  • Use middle shelf of oven. If results on middle shelf are unsatisfactory, experiment with higher or lower placement.
  • Place one or more cookie sheets on lower shelf of oven to break up flow of hot air through oven and thus dissipate "hot spots." Arrange pans charged with coffee beans on upper shelf above cookie sheets. Situate cookie sheets in relation to bean-charged pans so as to break up pattern of hot spots revealed by previous roast sessions. In other words, if beans in middle of roasting pan emerge darker than beans at sides, position cookie sheet directly below roasting pan. If darker beans are at back of pan, position cookie sheet somewhat farther back in oven than roasting pan, etc.
  • If beans take longer than 15 minutes to reach a medium roast or 20 minutes to reach a moderately dark (espresso) roast, or if they taste bland or flat, start with higher temperature on subsequent sessions.
  • Keep records of oven settings and elapsed time of roasts while roasting same amount of similar green beans. When you achieve a roast you enjoy use same oven setting and set kitchen timer for 2 minutes or so before termination of roast. You still must make final decision when to stop roast based on visual observation.

After-Roast Resting

Freshly-roasted beans are at their best anywhere from four hours to a day after roasting. Coffee fresh out of the roaster is still superb, however, so don't deprive yourself of enjoying it owing to gourmet obsessiveness.

Purchase the Swissmar A8200
Bravi 8-Ounce Rotary Drum
Home Coffee Roaster

  • Roasts from 2 to 8 ounces
  • Temperature- and time-controlled
  • 15 different roast settings
  • Quiet operation
  • Dishwasher-safe parts
  • 1-year limited warranty

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