I've been brewing Hayes Valley Espresso for several years, always at least a week passed roasting date. I've been doing 17.2g in, 24g out in about 30-35 seconds, for cortados. I've been getting a great bittersweet chocolate flavor nearly every time.

Last week I decided to switch things up and try the IMS Nanotech Shower Screen (switching from the Quickmill screen for my Lucca M58). I got some good results for a few days, but then something dramatically changed. Last week I was on the Jan 19 roast date (last Wed it would have been 13 days since roast).

Now, the resulting espresso is notably bitter. The crema is so thick, I can't make any patterns in it with the milk (in the glass, it's like a really thick foam). I noticed at the bottom of the portafilter, the espresso was coming out like a cone, as though it was super gassy. I decided to step back my changes - I used my old silicone ring with the new shower screen, then I went back to my original shower screen and ring this morning - the espresso is still coming out the same with the same bitter taste.

Could it be that the roast has changed? I am pretty sure it was both the 1/19 and 1/26 roast. This afternoon I plan to skip ahead to the 2/2 roast.

I've been trying so hard to slowly improve and maintain consistency. I felt like I was nailing the brew and getting good rosettas with the milk. So it's weird when things change dramatically like this. I can't tell if it's my equipment, myself, or the roast.

I can even see it in my daily record (I snap a photo of the glass every day), nice rosetta on 2/2, then bad from 2/3 through today.

Let me know if you have any suggestions or ideas here.

Could it really be that the roast is just off/different? I don't like change, and I've been using these beans for years, but will change if I need to.

Beans - Blue Bottle, Hayes Valley Espresso
Grinder - Mazzer Mini E
Machine - Lucca M58, both quick mill and IMS shower screens, bottomless portafilter.

Ordered 4 lbs from established vendor I use regularly. 1st lb was like always, second lb tasted way off, the color and roast level all seemed fine. Back flushed and still had same problem, the remaining 2lbs were all back to normal. Roaster replaced the bad lb. You may have a bad bag of beans.

I doubt that the shower screen has much of an impact on flavor especially since you're using the IMS.You may have gotten a bad batch or you need to rest the beans a bit longer.

For the excessive crema and latte art, try transferring the espresso shot from a shot glass to the desired serving cup or stir in the crema before pouring the steamed milk.

I fast forwarded to the next weeks roast, 2/2. The bag was like a balloon, like the others.. so definitely more gassing than I remember. Anyways, the espresso came out like a blonde cone again. Off tasting, bitter. I will ask Blue Bottle about this. But I will also start searching for another espresso I can get a regular shipment of.

Shot in progress


Shot before milk.

Looks like too fresh of a batch that needs to off gas more or maybe they did switch the blend to one that expresses more crema. They do not offer much transparency on what coffees they use in that blend so who knows? For the price, you can likely do a lot better for a traditional espresso roast.

I was seeing that kind of shot two days ago with beans that were even a week older. Puzzling. Also, I noticed the bags we re inflated like balloons. So maybe they were not degassing at all.

Sounds like faulty gas valves on the bags. Perhaps let the sit after they've been opened for a week and see if you still have an issue. Another fast way to see is grind and wait 30 minutes before pulling a shot.

Thanks for this suggestion. Grinding the beans and letting it sit for 5 minutes seems to be helping. BB must have had a large batch of bags with bad valves.