So my new espresso machine arrived yesterday afternoon and I have been trying to dial it in, but I am having a hard time. I am working with an 18 gram dose in an IMS Barista Pro 18 gram basket. When my grind size is set such that my 36 gram extraction takes 30 seconds, I get very bitter espresso due to bad channeling. If I grind finer, my extraction time extends to 40 seconds and is. still too bitter. I am still having channeling issues at that setting, but less so of course.

I think I am preparing my puck correctly, but obviously there is something I am missing. Some more details... I am weighing out 18 grams of fresh Black Cat espresso and grinding in a Niche Zero set at 10. I load to my portafilter, wdt, spread it out to be more even and then press with a Normcore tamper with a 30 lb spring (compressed all the way to get max spring pressure).

Any help to fix my channeling issues will be much appreciated as I am going through a lot of coffee trying to figure this out.

Why do you think it's channeling?

When my shots are too bitter, it is usually over extraction, so I think grinding finer might hurt instead of helping. Or, the brew water might be too hot. If the machine is new to you, playing with temperature is easy. There is no reason to think that the temperature on the pid gives the same temp at the grouphead as your previous machine, so whatever temp you were using before might not be relevant.

Good luck!

Meant to ask...what is the new machine?

Its my first machine, its a Profitec Go.

So I tried making the grind more course first, and that made the extraction much more bitter, which led me to suspect channeling. Looking at the next extraction with naked portafilter, it had 3 streams of flow and turned very blond on the left of the portafilter and the very center had an area where nothing was exiting. The extraction took about 20 seconds that time.

Hmmm. I am not knowledgeable about baskets...if that is not the stock basket, I would try the one that came with the machine. I believe some of the aftermarket baskets are high flow and more prone to channeling.

I'll try that and see what happens.

If you're getting "3 streams of flow and turned very blond on the left of the portafilter and the very center had an area where nothing was exiting" you probably have puck prep issues. I would ensure that the grinds are reasonably uniform and level with a WDT tool and then tamp only until you feel the grinds compress and start to resist you. You can tamp harder than intended with a force-indicating tamper if you continue to press after the indicator touches.

If that doesn't start to get you closer:

Sour/bitter confusion is very common. That is one possibility.

Have you had a shot of Black Cat espresso somewhere that you've liked? If you're tasting it plan, have you had any espresso at a cafe that you've enjoyed plain? I haven't had it in too long to know the current style, by "Chocolate + Molasses" suggests to me a rather dark roast which will be bitter by its nature. It may be that you just don't like the coffee.

Its possible I dont like the coffee, I havent had it before. But I generally like that roaster (Intelligentsia). I enjoy most espressos that I get at cafes. I also have a can of Illy classico beans I can switch to. Warming up the machine again now so I'll tamping more gently.

Certainly for me, dark roast + overheated brew water = very bitter.

I agree with Jeff and will also add that you might try skipping the wdt altogether, in the spirit of keeping it simple. I might be admitting something I shouldn't, but I have never once done a wdt. With a niche and med/dark roast, is it necessary?

Switched to the stock basket, which seems to require a coarser grind. I also switched to the Illy espresso since its a known commodity flavor-wise. I was able to finally get a decent shot. I'm not sure that the flow through the puck is totally even yet, but its much better and it tastes ok so definitely making progress.