How to Roast Coffee

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Tuning Your Roaster

HTR 1.09 Recap and Glossary


  • As a rough guideline, for every additional 500 kilograms of coffee you plan to roast per week, add another 50 square metres of floor area to your facility.
  • It’s essential that you set up your roaster correctly before first use. Don’t rely on the manufacturer to do a proper setup. Even small changes to the machine’s tuning can dramatically affect the way your coffee roasts.
  • The ideal drum speed depends on the size of your roaster’s drum. The correct drum speed enables maximal contact between the beans and the roasting gases, without risk of scorching or burning the beans.
  • Verify the drum speed on your machine by counting the number of times the drum rotates per minute.
  • The optimal airflow setting maximises convective heat transfer and minimises conduction. The easiest way to tune airflow is by means of the cigarette lighter trick.
  • Avoid changing airflow settings during the roast. If the airflow has been correctly tuned, additional changes are rarely necessary.
  • Ensure that the gas supply in your roastery’s premises has adequate pressure and can deliver enough power for the burners in your roaster.
  • Before roasting, adjust the gas-to-air ratio such that the burner produces a bright blue flame.
  • For temperature probes, we recommend using ungrounded J- or K-type thermocouples of approximately 3-mm diameter.
  • Position the bean temperature (BT) probe such that the probe tip will be immersed in the bean pile of the smallest batch you plan to roast.
  • Position the tip of the environmental temperature (ET) probe in the path of the airflow leading from the drum to the exhaust.

New Words

Creosote A black or brown residue that builds up inside roasting flues. The exhaust gases from a roaster contain tar and particles of smoke and chaff. As the gases pass through the chimney, they cool and the tar condenses onto the walls of the flue lining, forming a sticky surface that traps smoke and chaff particles.