Spent some time wondering where this question should go but as it will probably turn into a debate on how to grind beans, then "Tearoom" seemed appropriate…

I have a Gaggia Classic espresso machine, much used. The ground coffee goes into an aluminium cup with a double-layer base with a small gap between the two. The inner base has many fine perforations; the lower has one slightly larger hole. I gather this is to do with the production of "crema" – froth, to the rest of us. This cup sits in the portafilter (the removable bit with a handle) which has a double-ended spout to distribute the coffee into one or two cups. Inside the portafilter is a small plastic plug with a blind hole from the top and a cross-hole near the bottom. Apparently this helps to control coffee flow. It is apparently called the jet swirl emulsifier.

From time to time, the single hole in the cup blocks. I let it sit with some special cleaning powder and run the pump occasionally until, usually, the blockage clears. Today, it did clear, almost explosively, and coffee spayed enthusiastically out of the spout. Turned out that for whatever reason, the plastic plug thing broke into many pieces. Likely to cost best part of a fiver to replace plus postage. Can't 3D print in PLA due to temperature (80C or so). The only plastic rod in the workshop is acetal which is not suited for that temperature either. So, plan is to use an odd scrap of brass – fairly simple bit of turning and cross-drilling.

And so – the question (at last, I hear you say). Anyone have any idea of compatibility (taste, corrosion, etc) between hot coffee and brass? I can't think of any examples of seeing brass and coffee in contact; brass components on the coffee machine all seem to be plated. Thoughts?

Edited By Nealeb on 25/07/2023 15:36:50

Edited By Nealeb on 25/07/2023 15:37:57

Thanks for the comments. Yes, PEEK would be ideal – but I have none (used my small stock making a hot end for my first 3D printer!) and it's not cheap, would need to wait for online order to arrive, and I want my coffee machine back working again asap! It's on the limit for ABS, looking at Wikipedia data, but I suspect that the original was indeed ABS and, as the Wikipedia article suggested, that it became so brittle after maybe 10 years or more that it shattered into small fragments when hit by a sudden stream of coffee once the dam broke above it. Just picking up some fragments to try to take measurements showed me just how brittle.

I've just spent a little time making a replacement from an odd stub of brass which seems to work fine. I have had to guess dimensions and precise shape from various online outfits that sell this component as a spare part but I doubt that any of it is super-critical. I have also done what I should have done in the first place which is a quick Google search on brass and coffee. Seems that there are some cultures in which coffee is actually brewed in brassware, and there is even a suggestion that the zinc that leaches out in tiny quantities is good for your health. Well, maybe – I was more concerned about the copper leaching out and leading to heavy metal poisoning!