These are likely newbie questions but I couldn't find an answer using the search engine.

First question, I am using a naked PF - the cone that I get varies depending on the blend. On some blends I am getting a fairly large cone (maybe close to 2cm from bottom of basket) while others are very small (maybe 0.5 cm at most). Is this just due to specific beans or is it related to the freshness of the beans? On the one I get the large cone on I notice that this tends to get smaller or last a shorter time in the pull as the beans age.

Second question, on some blends I tend to get large bubbles on a latte within a few min (or less) after putting the drink together. There are no bubbles on the espresso and the milk is microfoamed, however the bubbles start appearing soon thereafter. Is this again due to freshness and the co2 being released?

Thanks

Typically the cone is larger on with fresher roasts. It's the CO2. I've gotten some huge cones on beans I've roasted myself and pulled the same day.

Not sure about your second question about the Latte bubbles but I think it's related. I'm been having the same issue lately in my Lattes. I suspected the microfoam, but now I'm thinking it might be the espresso. On some of the Youtube Latte art videos, the espresso looks like crap (no crema). Perhaps this helps with the surfacing mini bubbles.

Not really sure about the bubbles but the difference in cones can also be due to the pressure it's being brewed at. Lower pressure tends to form larger cones where higher pressure produces shallower ones.

The cone, and crema will vary by blend due to the bean make-up. It also changes as the bean ages. The cone will shorten and hold closer to the portafilter. Overly fresh beans will produce a huge cone because of the excess CO2. What does it all mean, not much, as long as the coffee tastes good. It is just one more tool in the box to help you diagnose your cup.

The bubbles in your drink, that is relatively normal. You could try pouring a quarter of the milk into the espresso, then give the cup a swirl and tap to help settle out the bubbles, then pour the rest of the drink. It could also be larger bubbles in the microfoam. A pitcher swirl and a couple of thumps on the table before you pour can help as well.

The cone is larger in fresher coffee, due to more carbon dioxide within the coffee cell. Within the espresso coffee cake and portafilter, the pressure is higher, ie, about 9 bars, therefore higher concentration of carbon dioxide. Once espresso starts coming out of the coffee cake, there is a sudden drop in pressure from 9 bars to 1 bar, atmospheric pressure, and the carbon dioxide effervesces, seen as a larger cone, or too much crema in the cup. This is similar to the bubbles in sparkling wine or beer once the bottle is opened.

Also, the cone size could be attributed to a coarseness of a grind. Different coffees (even different days of the same coffee) react differently to the same grinder setting. The finer the grind (within normal parameters) the smaller the cone you could get.

And another obvious thing that affects cone size: Basket Size.

I notice on the 53mm Vivlaldi, the cones are not nearly as impressive as on my previous 58mm E-61. And I'm not just talking about a "scaling down" effect. The cones are a different shape as well (not as long). You can see this in several of the videos of naked pours on both machines.

Is this also an indicator of a difference in taste?

Not sure I want to open that can of worms....but there it is.