rasqual Senior Member Joined: 29 Jun 2005 Posts: 970 Location: Chicago area Expertise: I love coffee
Espresso: *$ Barista, non-pressurized Grinder: SMP, KAP Vac Pot: Aeropress Drip: Porcelain Melitta 103 Roaster: "ring roaster", mod popper
Posted Tue Jun 13, 2006, 12:31pm Subject: Re: Polyester felt filtering material in Aeropress
We don't need to worry about chemicals used to increase flexibility. Polyester is pretty pure. The only real issue is binders and surfactants -- but yes, they're certainly an issue.
darrylr Senior Member Joined: 3 Apr 2005 Posts: 246 Location: Washington Expertise: I live coffee
Posted Wed Jun 14, 2006, 6:45am Subject: Re: Polyester felt filtering material in Aeropress
rasqual Said:
Ah. Well. ;-)
I washed the deuce out of the stuff, yeah. My biggest concern, as with all "reusable" items (including stock Aero filters) is the extent to which they act like a petri dish. A stock Aero filter dries out before it can begin hosting raucus bug parties, but this felt stuff doesn't dry so quickly. A dash of boiling water after rinsing seems a sane hedge, and before using as well. A sniff with the nose, too, I guess.
You are right, bacterial growth would become a problem over time and periodically boiling the material is a good idea. Also try storing it in the freezer between uses and run it under warm water to thaw.
By the way, I'm aware of another possible source of a filter material that may be suitable for the Aeropress. There's a company that makes a hugely expensive juicer called the Norwalk Juicer. It uses a hydraulic press principle where the produce is put in some kind of bag through which the juice is filtered as it escapes. I don't know what the bags are made of but it's not impossible they're some kind of polyester or similar polymer. In any event I assume they've chosen a food-safe material and I do know the material mesh is small enough to produce a fairly clear juice. You can find them by doing a Google search. They do sell the bags separately, as replacements for when they wear out. I believe they also do recommend periodically boiling the bags, although not too long a time since I think the heat damages the material.
rasqual Senior Member Joined: 29 Jun 2005 Posts: 970 Location: Chicago area Expertise: I love coffee
Espresso: *$ Barista, non-pressurized Grinder: SMP, KAP Vac Pot: Aeropress Drip: Porcelain Melitta 103 Roaster: "ring roaster", mod popper
Posted Wed Jun 14, 2006, 8:31am Subject: Re: Polyester felt filtering material in Aeropress
Interesting.
BTW, I just tried a woven Polypropylene fabric that's pretty astonishing, but I forgot to do it inverted (go figure -- Mr. Inverted blows a head gasket). Awesome stuff too. And I know someone with rolls and rolls of it.
No binders or surfactants in the propy, 'cause it's not a felt. ;-)
rasqual Senior Member Joined: 29 Jun 2005 Posts: 970 Location: Chicago area Expertise: I love coffee
Espresso: *$ Barista, non-pressurized Grinder: SMP, KAP Vac Pot: Aeropress Drip: Porcelain Melitta 103 Roaster: "ring roaster", mod popper
Posted Wed Jun 14, 2006, 7:27pm Subject: Re: Polyester felt filtering material in Aeropress
OK, it's official -- the polypropylene makes great coffee.
The material I used is too thick for the Aero, though (I had to file the bayonet tabs). I suspect I can get thinner. It's a woven fabric -- so tightly that there's no wash-through at all when the Aero is charged upright. The inverted method yields at least as much oil as with polyester. The material is much easier to clean than the polyester.
The basic problem with the polypropylene is that as a TIGHTLY woven fabric, when you cut a circle of it, it has a serious desire to fray and unweave near the edges. This would pose a problem for repeated use. The polyester, by contrast, is a nonwoven fabric, which doesn't fray around the edges at all, and therefore holds up very well under oft-repeated use.
I suspect I'd like the polypropylene a lot, but I don't know whether the edges of a cut out circle could be fused to prevent fraying. It would definitely lend itself to repeated use, given how easy it is to clean.
The materials could not be more different. Flow through the polyester is free -- in fact, you'd never imagine it could possibly filter out all fines. Flow through the polypropylene is almost impossible at normal pressures, but a conventional Aeropressing works great, not more slowly than paper at all.
rasqual Senior Member Joined: 29 Jun 2005 Posts: 970 Location: Chicago area Expertise: I love coffee
Espresso: *$ Barista, non-pressurized Grinder: SMP, KAP Vac Pot: Aeropress Drip: Porcelain Melitta 103 Roaster: "ring roaster", mod popper
Posted Thu Jun 15, 2006, 1:41am Subject: Re: Polyester felt filtering material in Aeropress
There are two reasons for inversion. The first would be a need to avoid amazing amounts of wash-through on account of using filters that do that. This is true with metal; it's also true with polyester. It's not true with polypropylene, and isn't really a problem with paper either. If this is the only reason for inversion, there's no need to PRESS inverted. Just keep it inverted for a bit until the fines swell (in the case of metal) or until you're ready to wind up extraction (in the case of polyester), then "revert" and press normally.
The second reason would be a desire to get the coffee oils in the cup. Plainly stated, uninverted pressing doesn't do it. The oils float in the bloom and get trapped in the puck. By pressing inverted, the bloom goes through the metal or poly first (not the paper), and then "reversion" dumps that into the cup -- provided you haven't made a mess all over the place first (that issue is the rationale for my pending mod). A draw of air with the plunger (readily possible with the metal and the poly materials) restores a head of air to the press, and the press can finish "reverted."
It's my opinion that the state of the art with the Aero has moved beyond metal filters. Unless their hole sizes drop below 25 microns, they just don't deliver anything better than a Clover does. Meanwhile, using the synthetic fabrics, I'm getting body and oils that are just impossible to obtain with an Aeropress and paper, and I'm getting zero fines -- something metal doesn't offer. Bear in mind -- I mean ZERO. :-)
JAB Senior Member Joined: 1 Mar 2005 Posts: 19 Location: Falls Church, VA Expertise: I love coffee
Posted Thu Jun 15, 2006, 2:47pm Subject: Re: Polyester felt filtering material in Aeropress
I've been thinking about this and what you need for the mod is more of the Aerobie's plastic pipe or equivalent (to hold the coffee that you press upward) but it needs to be attached to the cam that holds the filter. How would you do that, with heat-fast glue, or maybe some sort of plastic weld? If you figure out a good way I'll try it, but as everybody's been mentioning these health issues with the plastic fiber I'd be even more concerned about using a glue.
JAB Senior Member Joined: 1 Mar 2005 Posts: 19 Location: Falls Church, VA Expertise: I love coffee
Posted Thu Jun 15, 2006, 3:00pm Subject: Re: Polyester felt filtering material in Aeropress
Whoops, sorry Rasqual, I just read your exchange in the other Aerobie thread about no adhesives possible with the tube. Have you explored plastic welding though? I don't know much about that part of materials science but you'd have to figure there is some way of doing that. Maybe Alan knows?
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