Coffee Roasting by Weight Loss in Real Time

If a coffee roaster is light enough and small enough to fit on a scale, can I roast using green coffee weight loss in real time? Here’s my no frills trial …

Here’s some back porch coffee roasting experimentation with an air popcorn popper… can coffee roasting by weight loss actually work? Meaning… can I decide to roast to 13% weight loss, watch the green coffee lose weight to that point as I roast it … and stop the roast when I hit that 13% weight loss figure?

Playing around with this machine and coffee roasting some gadgets, I realized that my lightweight popcorn popper can fit on a gram scale. So how about taring out the whole “roaster” and try to do a roast using coffee weight loss, in real time.

This was more of an ad hoc experiment to see if it’s viable using low cost stuff I have laying around.

It also features a peek at my new project, which is a sleeve that fits in a specific air popper type and turns it into a very effective air coffee roaster for 120 gram batches! 

What I fail to mention in this video is that I only achieved 9% weight loss! I mention targeting 13% but since I started with 110 grams I have to do a little math to get weight loss as a %. If I lost 10 grams, so my roasted batch weighed 100 grams, thats only 9% weight loss.

(Quick weight loss formula refresher: Subtract the post-roast batch weight from the pre-roast green weight. Divide that number by the pre-roast green weight. To make it a % multiply by 100. See our “How to Calculate Weight Loss in Coffee Roasting” article for more!)

This isn’t a perfect test … just something fun to try. I was thinking about this simply because the popcorn machine I am testing with for my “coffee sleeve” project is so light, and has a compact footprint, I thought it would fit on the basic cheapo gram scales I use. It does … but the fit is tight.

What I tried after this … maybe even more silly, was to hot glue the popper to the scale. It worked well actually! I am interested to see if I can set this up better when the actual air poprcorn popper plus sleeve actually arrives from the factory (code name: Poppo!)

7 Responses

  1. Home Depot sells small chimney’s for oil lamps. I outfitted my Poppery 1’s with them. It will prevent the beans from flying out…the chaff will still escape. Just a thought. For a bit more development, you might think about raising your temperature about a minute prior to 1st crack, then lowering it back. You’ll get a more even roast.. I roast with an SR800 these days. Prior to that, I was one of the original Behmor 1600 beta guys.
    Good luck!

  2. I’ve been using an old Freshroast for about 20 years. It isn’t what it used to be. The original fan broke and it’s now being driven by its second rotary tool, whose speed controls the temperature. What surprised me most was not the idea of using a digital scale (the best kitchen tool) but that the popper is only drawing 95 watts. Amazing. I’m sure I’ve been using 1500 all these years.

    1. If I am reading you right – you modified the Freshroast and use a rotary tool to drive the fan – that’s amazing, and 20 years of use too! 95 watts sounds like just fan alone with no heating element. The one I am using is rated at 1400 watts and usually I see it using about 1250 total – most of that is going to be heating element.

  3. Thanks for this idea, I’ve been trying it with my SCTO setup. My rig is heavier, so I have to use a 5kg scale. The real time weight is a little different from the before/after weight of the beans, so I’m not getting exact weights in real time. But it still helps me monitor the roast, and better decide when to end the roast.

    I’m going to tweak my setup some more, only used the real time weight during 2 sessions so far, so a work in progress for me. Will see if I can get more accurate real time results.

  4. Hi,
    I bought raw coffee beans back in 12/21 and am just now looking to roast them. Are they still good?

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