Posted by: Andre | November 6, 2009

Homebuilt Sample Roaster

A few months ago, I decided it would be a good idea to try to build a low cost but effective sample roaster. My intention was to try to get something capable of producing samples for cupping, as well as be controllable enough for espresso roasting. After looking into Turbo Oven options and popcorn poppers, I decided to head over to the Aussie coffee boards (coffee snobs) and check out the popular “Corretto” named after it’s creator (or HG/BM). It’s basically an evolution of using a simple heat gun and stainless steel bowl (with wooden spoon to stir the beans). Instead of the stainless bowl, a bread machine is used only to stir and provide insulation (no heating element on the BM is used). You can check out the beginnings here:

The main points about this roaster that are attractive to me is:

  1. Low cost – this means it can work as a sample roaster in PNG for the office. At the farm a more simple drum (can) over a fire may work in a pinch.
  2. Hands free operation with a stand for the Heat Gun.
  3. Excellent thermometry if probe is placed properly.
  4. Very easy to control roast temperature by moving the height of the heat gun

A couple notes is that without a thermocouple or some temperature device your roasts won’t be repeatable and you could be more or less shooting in the dark if you’re planning to reduce heat between 1st and 2nd crack. I ended up drilling all the way through the front of my bread machine into the removable pan itself, this means that whenever I remove the pan I must remember to pull the probe first.

Bean charge size is dependent on both your Heat Gun output as well as your bread pan rated size. I experimented and ended up with 400g being my optimum. This charge size allows me a controllable ~8m to first crack with the ability to reduce heat as it approaches and extend 2nd crack 4-5m later.

These are just the guidelines I try to stick to, and so far have been working really well. Cupping sessions and notes will come in later posts.


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