Chemical bitterness after sanding Mahlkonig EK43s

Grinders are one of the keys to exceptional espresso. Discuss them here.

#1: Post by bzhang33 » Aug 01, 2019, 8:43 am

Hello everyone, this is my first post, and sadly it's me looking for help. :cry:

Recently, I followed the Hale method for sanding the grinder ( ... ur-grinder). But after this, all the coffee tasted bitter, it tasted like it was from some kind of chemicals. I suspected that it was either the Goo Gone or the multipurpose oil. I tried cleaning all parts and ground a bag of cheap coffee beans just to get rid of the strange bitterness. But it persisted and I was really frustrated, I'd really really like to hear suggestions on what to do next.


#2: Post by expy98 » Sep 12, 2019, 7:35 pm

Hey Boyang,

Did you resolve this issue yet? I haven't done so myself yet...

I'm also near Irvine, sent you a PM...


#3: Post by blkswn » Sep 13, 2019, 12:23 pm

Does this taste persist even in cuppings? (Just to ensure it's not a brewing error.) I would wipe the burrs and grinding chamber down really well with a damp cloth. Also would completely clean the rotating shaft, smaller rear chamber and spacer/spring. Maybe re-lube and clean it off again for good measure. I haven't had any off flavors post sanding, but did clean everything very thoroughly.

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#4: Post by truemagellen » Sep 13, 2019, 9:52 pm

Denatured alcohol, clean all of it with this. Get at hardware store.

You will need to run coffee through it almost immediately as burrs could rust as it will no longer have oils on it. Go ahead and run 5lbs of junk coffee through it.

If it doesn't resolve by then chemicals have impregnated info the plastic or began dissolving the plastic. If chemicals got into the motor although unlikely they could move their way into the grind path or give off fumes with the heat of the motor that could make their way into the bean taste. This will stop eventually but there is not much you can do if this is the case. The plastic might be harder to resolve.l and I'd suggest replacing parts if it doesn't go away.

These chemicals you used are so thin they can hydraulically make their way into every nook and cranny of the grind path.

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#5: Post by Terranova » Sep 14, 2019, 6:07 am

Another issue of the sanding method can be that you just transmit the run out of the burr carrier onto the chamber.
The alignment doesn't get better and warranty is void.
On the S version / newer version the chamber is CNC machined and much more accurate than the burr carrier itself.

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Randy G.

#6: Post by Randy G. » Sep 14, 2019, 1:22 pm

As a side note, I would never recommend using GooGone on anything that would be used for food. Whether that is the source of this problem I have no idea.
Espresso! My Espresso!