How to Roast Coffee

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Tuning Your Roaster

HTR 1.05 Tuning the Burner

Once your roaster is installed and you’ve verified that the gas supply is adequate to power the burner, you need to tune the burner to ensure that it burns the gas as efficiently as possible. To do this, you have to adjust the ratio of gas to air passing through the burner.

If there isn’t enough air in the mix, the gas will not be able to burn completely, resulting in an orange or yellow flame. The yellow colouration is the result of small carbon particles (soot) in the flame, which glow at high temperatures in the same way the filament of a lightbulb does.

A yellow flame releases soot and smoke into the roasting gases and also reduces the power available from the burner. Blue flames burn much hotter than yellow flames: natural gas burns at around 1950°C (3540°F) if there is sufficient air available, while incomplete combustion with a yellow flame produces a temperature of only 1000°C (1830°F).

Adjusting the gas:air ratio may be as simple as turning a screw on the burner, or it may be a more complicated operation requiring the assistance of a technician. While the burner is lit, you should adjust the amount of air coming into it until the flame appears bright blue. A small amount of orange visible at the flame tips is acceptable, but the flame should be 90% blue.

Using more air than needed will reduce the amount of gas available to the burner, so adjust the valve until there is just enough air to ensure a blue flame, but no more.

Once the gas:air ratio is set up correctly, you may need to adjust the gas valve to ensure that you have access to the full gas pressure at the maximum setting and that you have as much control as possible over the gas pressure at low settings. The method for adjusting the gas valve depends on the type of roasting machine you have. Check your instruction manual or consult your roaster manufacturer for advice on tuning this setting.