My cleaning routine for the Aeropress used to look like this:
Use the device.
Discard the puck and wipe the plunger with a few sheets of kitchen roll.
Rinse the Aeropress under a tap and place in the dish rack, ready for use.
I would do a full clean of the device toward the end of the day, after I had consumed and enjoyed my last coffee for that day. This became my routine for months. I then started to think about the plunger. I am unsure what brought the plunger to mind but I got curious about how it should be cleaned. I put my nose close to the plunger, took in a breath, and realised that even after cleaning there was a smell of stale coffee. This, as you can imagine, was not a pleasant discovery.
Up until that moment, I had not read much, if anything, on the need to clean the plunger. Because the plunger is stuck onto the device more than the other pieces (i.e. the filter cap is easy to remove), I forgot about cleaning the rubber in the plunger. I set out to do a deep clean of the plunger to get rid of as much of the smell as possible. The concern was not just the smell: what if there were still oils inside the plunger that could leak into my brews?
To take off the Aeropress plunger, you need to use a bit of force. I was worried about tearing the rubber but this did not turn out to be a problem. After some pulling, I removed the rubber from the plunger and took a look. There was a bit of debris inside the rubber, almost like a slime. I am unsure how long it had been there but I know that I do not want slime near my brew.
I looked online for cleaning recommendations and I concluded the easiest way to clean the rubber was to wash it thoroughly in hot, soapy water, and then leave the rubber to steep in the water for some time. I did this and left the plunger for at least 30 minutes. I forgot that it was in the dish basin for a while. I went back and smelled the plunger again. There was still a somewhat off smell but: (i) it was not nearly as potent as the last one and; (ii) all of the slime inside the rubber that had built up was gone. I could maybe have used a cleaning product like baking soda but I did not want to risk damaging the rubber.
I pushed the rubber back onto the plunger—it was somewhat odd seeing the plunger without the rubber on the bottom—and my Aeropress was ready for use.
In short, I'd like to remind you that you need to clean your rubber plunger. I am not sure how often you should clean the device but I got away with waiting over six months—with use twice daily almost every day—before needing to clean the plunger. Keeping your equipment clean is in the best interests of your coffee making; you do not want old oils to get into your brew.