What is the Sticky Stuff on my Aeropress Coffee Maker?

Black plunger on the Aeropress coffee maker sweating a bit? What is the sticky film and is it harmful?

I kinda freaked out the first time I saw this weird sticky secretion on the rubber plunger of my Aeropress. I hadn’t used it in some time (it was a spare one I keep in my trailer).

Don’t worry! It is harmless, and can be cleaned off … though it takes some effort. I use hot water ans soap. The stuff is very sticky so it might take repeated washing and rinsing

Quick video showing the sticky Aeropress layer I am talking about!

What is the Sticky Stuff on my Aeropress?

From the maker: “The sticky excretion from your seals is a combination of coffee oils and mineral oils that tend to leach out of seals that have been sitting unused for awhile and this is particularly true if they have been sitting in a warm place.”

Can I clean off the Aeropress plunger?

The sticky material can be washed off but it is not easy.  Use hot water and soap … that and some scrubbing was all I needed to clean this one.

Is the sticky film on the Aeropress harmful?

From Aeropress: “The coffee oils are harmless and the mineral oils are also harmless.” “They are required for the food grade materials we use in making the AeroPress.”

Can I continue to use the Aeropress after I clean it off?

Sure, no reason to buy a new one!

What if the plunger is worn and loose when I plunge the Aeropress?

Then maybe you want to buy a new one. And Sweet Maria’s sells spares!

How should I clean my Aeropress?

I use soap and water. I don’t use coffee cleaning chemicals, and definitely do not use the strong ones designed for metal parts, like espresso machine cleaner. If you want to use a cleaner, use one made for coffee brewers that have plastic parts, like Urnex Cleancaf for Brewers.

5 Responses

  1. Thanks for the informative post. My aeropress sat unused on a shelf for a year. I was mystified this morning to find the end of the plunger covered with sticky residue.

    1. Yes – i was relieved to find it was natural, since the plunger is made from natural rubber. Still – wouldn’t want that in my coffee! I used hot water and soap to remove it. I also found that when I left an aeropress in a sunny warm spot, it would develop this sticky stuff sooner. (but sooner means a couple months of non-use).

  2. You mean that white silicon type looking Teflon? I think it’s called PFAS or PFOS. It’s in your water!

    1. Hi Gene – I’m not clear. There can be a clear sticky layer that comes from natural rubber when it sits unused, and that’s what we are talking about. Silicone is not an issue. Teflon is not silicone. The aeropress doesn’t have either, so not sure how it relates.

  3. Probably silicone and mineral oils leaching out and plasticisers. These are not the best for you but probably aren’t going to give you any acute or long term health effects (it’s all food-safe after all) so I wouldn’t be too concerned as long as you clean it off.

    I just took my Aeropress out of storage during the past couple of years and cleaned it all off with isopropyl alcohol. Comes off very easily. Note that this may also degrade the rubber more quickly but if it gets too bad to use you should probably just buy a new plunger tip anyway. It’s definitely not likely to have PFAS in it.

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