I've moved up in the world and now work in a place with a communal Keurig machine in the break room. Everybody buys their own K-cups, so there's no fighting over who paid how much for their coffee dues, and we all get to make our favorite flavors. Heaven. Seriously. It's the small things.
After spending too much money on K-cups, my coworker and I each picked up one of those DIY-K-cups from Bed Bath and Beyond (with a 20% off coupon, naturally). The packaging says you just fill it with your preferred ground coffee and pop it into the machine for a delicious cup of coffee for a fraction of what the official K-cups would cost you.
The thing is, we can't get it to work. We get coffee, yes, but it's terrible. Even filling it to the absolute maximum line and setting the Keurig for the smallest cup (6oz), the result is extremely weak. We've tried putting more coffee, less coffee, finer and coarser grinds, and different brands of coffee, but it always comes out like a cup of watered-down coffee. Watching the process closely to pinpoint the problem, I noted that the liquid coming out of the Keurig with one of these things in place was a lot lighter in color than when a K-cup was in there, so I put in a K-cup (since I wanted a decent coffee!) and watched the machine to confirm my suspicion. Sure enough, the coffee looked dark at first, but gradually got lighter until it looked as watery, right at the end, as the stuff coming out with the Solofill cup.
Hypothesis from the peanut gallery in the break room: Maybe the K-cups are super-packed with much more coffee than we could fit in the Solofill! Considering how everyone who walks up to the machine with a K-cup is always unconsciously shaking their little coffee pod like a maraca, I knew this couldn't be true: if it was packed really tight, it wouldn't make noise when shaken. The group wanted proof, of course, so I fetched a sacrificial K-cup from the box of freebies in the office supply closet, which is stocked with decaf and flavors nobody likes. My victim: spicy eggnog. Eeeeeewww.
It was obvious, once I held the pod up to the light of the window, that it was only half full. The interesting thing is, it's the top half that's full, and the bottom is just air. I cut it open to confirm that it was just air and not a filter or something, and yes, just air1. The top half of the cup was taken up by a thick papery filter full of coffee.
Second hypothesis from the peanut gallery (we have very chatty peanuts in our group): maybe it's not real coffee in the K-cups! Maybe they put instant coffee in there to fool us! The problem with this, though, is that a used K-cup still has coffee in it. Yes, we dismembered one to check.
New hypothesis! Maybe there's a combination of instant coffee and real coffee in there. This would explain why there is still coffee in the pod once it's done brewing, and explain why the coffee is darker at the beginning, because the water dissolves the granules right away while the rest of the coffee does its thing. My goodness, what a sexy hypothesis! How to check? We tore the lids off the new and used K-cups to compare the volume of coffee grounds, because obviously the instant coffee would have melted away. Weighing them was immediately rejected, because one was waterlogged. Instead, we dumped out some of the dry coffee from the new pod and compared it to regular ground coffee. It looked the same, but just to be sure, I sprinkled some of the K-cup coffee in a coffee cup and added warm water to see if it would dissolve. It did not.
So now we all know what goes on inside a K-cup, but aren't much closer to making decent coffee with the reusable filter. The current hypothesis is that the filter isn't fine enough and the water goes through too fast, not bringing enough coffee flavor with it. Cramming more coffee into the Solofill just causes an overflow problem, so that's not the answer. The paper filter in the real K-cup is very thick, so we're thinking that's the key.
They sell other kinds of multiple-use Keurig pseudo-pods2, so the new plan is to buy a couple of different ones and see if they work any better. All of them seem to have similar reviews online, so it's hard to decide what to try, but with our filter hypothesis, I'm going to look for one with a very very fine mesh.
1. I suppose it may have been helium. I did not run it through a mass spectrometer.
2. Pseudo-pods, as in "false pods" not as in "a temporary protrusion of the protoplasm, as of certain protozoans, usually serving as an organ of locomotion". To my knowledge Keurig coffee machines are not amoebas.