I acquired a used Gaggia Classic and a naked portafilter and the first six shots were gushers that sent jets of scalding espresso across my kitchen. I finally got the grind somewhere where most of the jets are suppressed, but I'm getting a really foamy pull and I can't really tell when/if it is blonding because the density of the liquor coming from the portafilter is so low. I'm dosing with 16 grams into a double basket and using a little less than half a turn on an OE pharos for coarseness, and I'm getting 1.5 oz in 16-20 seconds. Taste is decent to pretty good, but there is something wrong with my settings or technique.

Should I be backing off on grind fineness and upping dose, or is there something else wrong?

Edit: I probably shouldn't rule out the beans. They are Sumatran peaberry that I roasted up Friday evening. I'd estimate city+. I got lucky with dialing in a grind for a Yemen coffee last night, and had a better looking shot, but the grind setting got moved so I had to estimate where it was.

There are a couple of things you can check. I don't own a Pharos, so hopefully a Pharos owner can chime in. However, on my HG One I had a similar problem. I had the grind set very tight but there was a vertical alignment issue I diagnosed. Once that was fixed I was able to get a proper espresso grind. Essentially, I was trying to extract with a press or drip grind.

You've already mentioned that it might be the beans. I was going to recommend checking that. I recently tried extracting with some City to City+ beans and got gushers. I'm starting to think light roast might not be great for espresso at low doses (14-15g). I upped the dose to 17-18g and the flow was perfect, but it tasted awful. Maybe someone with more experience in light roasts can chime in there.

And lastly, when using a naked PF, you might want to use WDT. I found it seemed to reduce the amount and ferocity of the spritzers. I say seemed because it may have just been that my grinder burrs weren't seasoned yet.

Good luck!

I only had 8g of the Yemen coffee left, so I blended it with some Kenyan Kirinyaga AB stuff which I stopped at City on. Damn, these guys are hard to grind. I WDT'd the basket (16.5g dose), but still got a singular jet and it extracted fast. Definitely an improvement from the first few shots yesterday, but I think that's primarily from the fine grind. It was still quite foamy and went a bit fast. I'll do another shot with what I have on hand with a heavier dose, but I'm not sure how much more will fit in the basket. I'll also grab a nickel to check headspace.

I roasted up a new batch of Brazilian coffee, stopping the roast at the first audible sign of second crack (FC->FC+). I'll try it out tomorrow morning to see how it does.

The espresso machine is used, and the OPV has been adjusted. If the setpoint was lowered too much, what effect would that have on the extraction?

Initial setup and learning is a bit of a pain with only 75g of each roast. If I have time tomorrow, I'll swing by one of the good local roasters and get a full bag.

Edit: I went up to 20 g with the Kenyan beans, and still got a thin, sour gusher. I'm inclined to dump the beans. I got impatient and tried the Brazillian beans (back to 16g). They grind so easily, and the espresso pulled at the right rate, but tasted a bit burnt.

The earlier Yemen and Sumatran beans at least resulted in decent espresso. I do think there may be a few too many variables here at the moment.

You're probably right about the variables. At the risk of confounding things even further I want to mention that a Titan class conical such as your Pharos requires quite a lot of grinding to season the burrs. Has it had that seasoning period already?

It's seen a little over 2 pounds of coffee total.

I managed to choke the machine with the Brazil beans. I backed off a little on the grind and got what I'd consider to be a drinkable ristretto. The burnt taste subsided overnight. I got a tight, but not particularly even cone with some striping. When I looked at the puck, I did see a pencil crater, so there's definitely some channeling going on.

I went to a local roaster/coffeeshop, got a bag of beans to play with, and talked to them about selecting the grind and dosing. One of the baristas actually has the same grinder for his home setup. It at least seems like I'm on the right track.

The aeropress funnel makes a pretty good dosing funnel.

If it's only seen a little over 2 pounds of coffee, my recommendation is to drink and be merry! Your results in the cup will only improve as you grind more coffee.

Do some looking around the forums on "puckology" or diagnosing puck defects and you may find that it's very difficult, if not impossible to tell anything about a shot by looking at a spent puck.