Since I started using unpressurised baskets with my Breville Café Roma, my espresso has had a small amount of coffee grounds in it as a result of the larger holes in the Bar Italia (unpressurised) baskets. IMO, its only annoying because you cant drink (and enjoy) the last sip out of the cup. However, a friend of mine suggested that it also adds a muddy flavour to the cup - I havent noticed this, personally, but could imagine that its there.
Photos - original basket on left, unpressurised on right (FYI, Silvia baskets, for example, have far smaller holes than even the one on the left):
My friend suggested using a little square of filter/kitchen paper at the bottom of the basket. I was dubious, but I tried it, and it HAS reduced the amount of grounds in the bottom of the cup. Im not sure if its improved the flavour or not.
My question is, how do you think this would effect the shot? Im using thin, dimpled, generic brand paper towel, and placing a square of it in the basket before dosing. It hasnt effected the amount or quality of the crema, nor the speed of the shot. The flavour is good (for the CR) and possibly different from without paper, but I cant say how... When I bump out the puck, the paper has a slight hole wherever it touched a basket hole, but no tears or anything.
Any ideas as to how this method would effect the shot in any way?
Youd reduce some sediment and particulate matter but probably also reduce some of the oils that get through which may result in a less accurate reproduction of the coffees original flavour and a less flavourful brew all round. Ultimately however let the taste be your guide but dont be afraid to switch back from time to time because your palate will probably change with time and in a few months time you may taste flavours you cant presently pick. Whenever I have drip filter coffee I prefer it with a paper filter as it doesnt have that muddiness to it, and in those situations Im not so concerned about the absolute characteristics of the experience as getting a drink I can enjoy.