Because I cant wait until the unpressurised baskets arrive for the Breville, I decided to try cleaning out the pressurised ones. Sure, I could take a grinder to them and turn them into unpressurised ones, but thought Id be up for a different kind of challenge.

I think Ive mostly succeeded, though its not a quick or perfect fix by any means.

Before:
- could easily choke the machine (Breville 800ES) with a light tamp of decent, but pre-ground coffee (lets say about 3kg pressure)

Cleaning:
- bowl of hot water
- powdered cream of tartar (ie tataric acid)
- goo-filled, slow-running pressurised baskets

Dissolve as much cream of tartar in the hot water as you can -- keep adding a little bit and stirring until all dissolved. Dont worry if you have a bit left on the bottom of the bowl. Now, gently lower one basket at a time into the hot slightly acidic water. You want them to float, so that the hot water gently percolates up through the single hole in the base, and then up through the cavity. Eventually, the basket will sink. Leave it there.

Every time I made a coffee, Id pull the basket out of the soak, blast a couple of shots of plain hot water through it to clean it out, and then fill/tamp/pull the shot. Id follow up by putting another shot or two of plain water through after the coffee. Invariably, the water to come out of these "plain" shots was brownish and had a least a few fines in it.

Once the coffee is made, let the basket sink back into the (now-cold) soak solution.

Its taken about a week, but I can now pull a shot of the same (yes, pre-ground, I know) coffee after a reasonably medium tamp (say 7kg) without choking the machine.

So, just in case youre not getting coffee out of your pressurised baskets as easily as youd like -- give this a whirl.