After reading the extremely interesting and though provoking 2-part blog post from Maxwell Colonna-Dashwood of Colonna & Smalls coffee shop in Bath UK, I decided to have a play around with heating up beans before grinding!

Here are Maxwell’s articles, in summary he wondered why he had to change his grind settings throughout the day at his cafe. The result is seems was not that the grinder was heating up but more that the beans were heating up and changing their properties and as a result fines production was reduced, very interesting!

Grinding – The Dark Matter of Coffee – A Think Piece

The Heat is On – More Grinding Puzzles

So my kitchen is usually really cold and I store my roasted coffee beans in there next to my grinder. So if grinding them cold means more fines and less consistent particle size then that’s what I’ll be getting which is not ideal. My first experiment a couple of weeks back was to take a portion of beans in a metal container and heat it over the gas hob for a short while until the beans felt warm to the touch. So I heated my first batch and ground them up. I noticed a couple of things, firstly there was next to no static on the beans, secondly there was next to no visible chaff, thirdly there were no clumps visible….. I pulled an espresso and the flow was much faster than without heating too.

I tried the same method on a filter grind and tested on my batch brewer and the chemex, draw down was quicker and seemed more even.

Something’s going on for sure.

Since heating in metal tubs over a gas hob is less than ideal and completely non-repeatable I turned to the microwave. I had serious reservations about putting my lovely coffee beans in such a device however I needed to know what would happen. I heated 20g of beans for 30s on full power (1000W) in an airtight plastic tub. The beans came out warm to the touch. I ground them up with exactly the same results as before, less static, less chaff (visible) and fast flow on the espresso than the cold beans…

From Maxwell and Chris’ explanations we could be seeing the beans becoming more pliable as they warm, this results in a much more even breakup when ground. This is really interesting and something to investigate further, however, I have seen no information with regards to whether this is actually affects the taste of the resulting coffee and I’ve not had chance to test the two side-by-side at the same brew ratios. Maybe one for the weekend…..

4 Comments. Leave new

  • I agree heating the beans before grinding effects the timing of the shot. Has anyone concluded an appropriate temperature range for heating espresso beans before grinding.
    I have tried microwaving beans which seems to work. The beans do not absorb a lot of the RF energy so the timing of the heating is not critical. Just wondering how far to go the heat? My observation on the taste is that bitterness is reduced. Any updates on this technique?

    • Hi Bill,

      I don’t think that there has been too much more research done in this area. I think that the main schools of thought are that cooling beans increases fines, fines make espresso therefore this is more desirable. The other school says that heating beans reduces fines which in turn increases clarity but lowers body and this is more desirable. Obviously the third camp is just leave them be 🙂

      I’m in the camp of leaving them alone at this point but it was interesting to have a play and understand what a simple thing like this can change if required.



  • Bill Barrett
    March 24, 2016 1:38 pm

    I have a K10 WBC and warming the beans allows me to grind finer to keep the same shot timing. Wondering if this reduces boulders? The shot seems smoother.

    • I believe that the current thoughts are that the finer you go, the more even the grind and the smaller the particle size distribution.


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