In the past I just tamped and poured the shot. But the other day I was using the last of my beans, which were a month old, and not giving great results. I decided to wipe off any minor coffee dust residual on the sides of the filter, and then blow out the remaining coffee particles. What I found has been a total surprise. An espresso that has none of that bitter flavor. Even on long pours. This has been reproducible for every pour in the last two weeks.

Now I'm wondering if anyone else has found this, or can deny this. I'm always leery when I think I've made a new improvement in my technique.

Are you referring to the very thin layer of coffee grinds that is sometimes left on the basket wall after tamping, prior to locking in and pulling the shot?

In barista competition, it's SOP to turn the basket upside down over the knockbox to get rid of the stray grinds.

However, I doubt that this 1/10th to 1/5th gram of stray coffee is a lot more bitter than the other 16 grams of identical coffee in the puck, i.e. about 100 times as much of the same, even if it does end up grossly over extracted. I'm guessing the taste improvement is due to some other change you made. Of course, the few stray grinds could be the snowball that triggers some catastrophic espresso avalanche, and the taste could really be completely transformed. That would be interesting.

Makes no difference for me on any of my machines and/or grinders. Those stray flecks of coffee would get compressed into the puck during the extraction anyway. I wipe off the rim of the basket and ears with my hand before I lock it in but that is to prevent ware on the gasket and lugs. I will occasional turn the portafilter over to let any loose grounds drop out but what is stuck to the sides of the basket stay, and there is always some stray grounds laying on the surface of the puck. There is the chance that it has some impact on your shots but my observation is that it does not. Your change in results are probably from some other variable.

another_jim wrote:In barista competition, it's SOP to turn the basket upside down over the knockbox to get rid of the stray grinds.

I used to do this before every shot, but I found that with certain light roasts, this causes the entire tamped puck to fall out into the knockbox / sink / floor. Gives a new meaning to "sink shot."

portamento wrote:I used to do this before every shot, but I found that with certain light roasts, this causes the entire tamped puck to fall out into the knockbox / sink / floor. Gives a new meaning to "sink shot."

I figured I'd try the same thing and it happened to me too. Not too happy that I had to start from scratch again.

As Jim and Dave indicate, there is no reason why a few stray grinds on the filter basket should make a difference in the pour. I certainly have never observed anything worth mentioning.

OTOH, I typically brush stray grinds off the lip of the filter basket after tamping, and then briefly invert the basket. The puck falls out on very rare occasions, on the order of once a year (less than one in a thousand preps). This has been the case with baskets of different size/shape/diameter, and many different blends and roasts. If inverting the basket causes the puck to fall out regularly, I'd suggest the possibility of a poor seal between the puck and basket sides. A poor seal could be caused by a variety of factors, including tapping, polishing, or an uneven distribution of grinds in the basket.

Another possibility is that by wiping out the last grounds you also dried the basket. Some folks have said that a wet basket could lead to some bypassing.

You should always dry out your basket before you dose. What the OP is refering to is blowing/wiping the leftover stray granules of coffee from the top of the tamped puck. Those pesky little flecks that end up between the tamper piston and the wall of the basket.

Gregg K wrote:II decided to wipe off any minor coffee dust residual on the sides of the filter, and then blow out the remaining coffee particles. ...

You're probably taking several short little puffs when blowing the coffee particles out of the basket, not one deep breath as if you were preparing to blow out all the candles on your birthday cake. The stray grounds are being blown up your nostrils, influencing your sense of taste/smell.