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How does the humidity affect the length of time required to reach a good light roast in a gas fired roaster.

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I believe heat and humidity play a key role in the role of energy transference in the roaster. I roast (professionally)in a very dry climate and find it easier (more forgiving) to roast in a climate that generally has a more humidity.

Here is a link to a conversation about heating and humidity that hopefully will help answer your question.

I think the 3rd answer is the most appropriate in its relation to heat transfer and "other" objects in a room (i.e. Coffee beans).

How air humidity affects how much time is needed for heating the air?

  • From the tired answer it sounds like we can we logically conclude that in a humid environment you'll use more gas. Do you agree/find that to be true? Do you think humidity makes a lick of difference for someone who is using infrared? – Nick Dec 1 '16 at 2:18
  • Difficult to say in roasting. – roasterbob Dec 2 '16 at 15:56
  • it's very tricky to answer because you are not only worrying about the humidity in the environment in the roaster you need to worry about the humidity/moisture content of the actual green bean. But yes, It should take more heat at higher humidity, but the energy transfer should be easier. I am not certain about the infrared option, but I don't think it should be an issue. heat is heat. – roasterbob Dec 2 '16 at 15:59
  • But with infrared you would predominantly not be heating the air. Yes the air would get hotter as the mass in the chamber absorbs and gives off heat. But in theory it should be less sensitive to variations in humidity, right? – Nick Dec 3 '16 at 0:19
  • you are still heating the air mass between the flame/heat source and the drum (if using a drum roaster). the heat source no matter what never comes in direct contact with the beans. you are always heating the air which is a huge component in roasting. Convective heating the major form of heat transfer in the earliest part of the roast so having differences in humidity will greatly affect how things progress. – roasterbob Dec 5 '16 at 15:54

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