I have been making espresso with a Rancilio Silvia for quite some time now. First couple of years thinking that espresso was supposed to be a bitter harsh drink, until I started to master the 30 seconds pulls in a bottomless portafilter without channeling using freshly home-roasted coffee. With trial and error I got to the point where I could consistently make nice tasteful balanced shots. The only thing that was bugging me was that the range of brew ratios that produced nice results were very narrow, I could do between 100% and 70% ratios with pulls of between 25-35 seconds and it all tasted great.
However, as soon as I would get much below 70%, the coffee got watery and very bitter.
I was using a dose of 16g in a double basket and adjusting the grind to get the ratios I wanted in about 30s.

Recently, with a new machine (a E61 HX) I kept using a 16g dose and had pretty much the same experience as with the Silvia. After some more reading here on the forum I decided to try out a dose of 12g, the Vario was not set up to grind as fine as needed so some re-calibration was required, but I am now getting 24g shots out in 30s and the taste is nothing like I was previously getting with ratios of 50% using the higher dose. I am now finally getting something that is drinkable with balanced tastes at ratios of 50%.

Can someone explain what is going on? With the 16g dose I had to grind much coarser than I do now, but why were all the shots undrinkable at brew ratios below 70%?
Is it perhaps that with the grind that coarse the grinds quickly get over-extracted?
What would it take to make a better shot at lower brew ratios with a 16g or 18g dose, is it the basket? If it is the grind that is causing this, I assume that a triple basket would allow me to grind much finer at higher doses ?

I can't give you a concrete answer, but my espresso got better once I started leaving headroom in the basket. Before, I think I was overfilling the basket, so the grinds were hitting up against the screen before the extraction. Now, for an 18-19g dose, I'm using a 20g VST basket.

That was also one of the first mistakes I was making back in the days. With the Silvia I used to put so much coffee in the double basket that it was touching the screen already when loading the pf into the machine. Putting the pf in and taking it right back out was already leaving a print from the screen on the puck.

However with the 16g I was still within the limits of the basket I started using, the LM ridgeless double.

There are many benefits of a finer grind. (Less overall variation in particle size, more surface area on the coffee, short path from the center of the grind out for extraction...etc.) All makes a positive difference imho.

The Slayer guys get a lot of benefit by going finer. You may find these videos interesting:

Keep in mind Slayer is doing slow flow pre infuse as well, which allows a finer grind again, and for the coffee to bloom, off gas....), so you will only get some of the benefit. Once you start going finer, it will become much easier to over extract, so you may only find yourself doing it for light, and some medium coffee's (say up until a city roast).

From (1:45 to 2:03) You can control pre-brew to still use large doses, but you can down dose

Pulling shots on the slayer... talking about finer grind, and taste changes...

Pedro,

You're not supplying enough information to get an informed diagnosis. Without knowing more, my best guess is channeling. You got better results from dosing lower and grinding finer. The dose probably isn't the operative agent of change. Pucks made from finer grinds are less prone to fissures. Furthermore, you have to consider that your results are idiosyncratic in that everyone and his aunt gets fine results from 18g+ doses in an E-61. So whatever the problem, it isn't dose in and of itself.

Your hypothesis that coarser grinds are causing over extraction is wrong. Everything else being equal -- very much including flow rate -- coarser grinds tend to under extract relative to finer grinds. In any case, the degree of extraction should be judged by the blonde point, and the shot cut before over extraction.

The basket is only one side of the head space equation, the other is the group. Some groups allow more head space than others.

One of the problems with other baskets -- even "good" other baskets like LM and Synesso is lack of consistency. If you want to compare results with other people, or consistency from basket to basket with your own equipment, I suggest buying VST or Strada baskets and talking with other people who are using the same group.

If ever there was a "standard," it's the 18g VST.

The best way to check and adjust head space with any machine/basket combination is one of the coin tricks.

Triple baskets are cranky. Perhaps not quite as bad as single baskets, but they're more often a problem than a solution.

Evaluating Silvia over/under extraction results is problematic, if only because -- without a PID -- Silvia temping is inconsistent and erratic. I don't know how long you've had your unnamed E-61, but the longer you use it the more you'll find you learned more about using the Silvia from using the Silvia than you learned about making good espresso.

Rich

Thanks Rich, I will try some other baskets as well.
I believe I have the channeling under control, i will revisit the higher dosing soon and see if I can get something drinkable closer to 50% extraction ratio.
My new machine is the ECM Technika. It is really nice to see how the coffee starts to come out really slow almost in slow motion before turning into a regular flow. With the Silvia as soon as it started coming out of the bottom of the filter it would get into the steady flow almost immediately.

I understand how you will extract less from the coffee if the grind is coarser. My reasoning for suggesting the coarser grind was causing over extraction was as follows: With a coarser grind there is less surface for the water to interact with the coffee and you will reach the point sooner that the water has extracted all that it can, the water that comes after that point will only be able to reach the parts that are already fully extracted and produces an over extracted flavour.
Anyway that is just me guessing at how it could work and I am happy to stand corrected.