Failing Nickel Test with my Rancilio Silvia Pro

#1: Post by **Parm** » January 9th, 2022, 7:43 pm

Trying to get some advice on my technique as one problem I'm running into is my dry espresso puck touching the dispersion screen on my Silvia Pro. I'm using a bottomless portafilter with an 18g VST basket and noticing that the majority of the time when I put the portafilter into the machine and take it back out while dry, there is a faint impression of the shower screen on the puck. When I do the nickel test, the nickel is depressed almost its entire thickness into the puck at 18g dose. At 17g it still leaves an impression, albeit smaller, and by 16g the impression has mostly gone away.

My shots are tasting okay and I'm not getting any major channeling (an occasional quick spritz every few shots), but I'm still concerned that I'm not leaving enough clearance between the puck and the grouphead. The fact that I'm still seeing some faint imprints even at 17g and 16g makes me wonder if something else is amiss, as I assumed an 18g basket should be able to take an 18g dose. For reference, I'm using the Bravo tamper, so I assume my tamp depth and pressure is sufficient. The coffee I'm using is Dragonfly's Cream Dolce, so on the medium side.

I did take the shower screen off to check for any issues and it looks good as far as I can tell. I've noticed the screen doesn't seem to sit 100% flush against the dispersion plate. If you put pressure on a certain part of the screen it'll seem to hug the dispersion plate tighter than the other side. It's hard to describe but easy to see if you're looking at it. I've ordered an E&B shower screen which I was planning as an upgrade anyways. I assume it's just a small manufacturing issue with the screen that came with the unit, rather than an issue with the dispersion plate itself. Typically the screen impression will favor one side of the puck, so my guess is that the screen itself isn't resting 100% flat and potentially sits a mm or so lower on one side.

Anyways, just curious if anyone else has encountered this and whether I should be concerned about it or looking to make any adjustments to the machine to prevent it from happening.

#2: Post by HB » January 10th, 2022, 10:12 am

Parm wrote:The fact that I'm still seeing some faint imprints even at 17g and 16g makes me wonder if something else is amiss, as I assumed an 18g basket should be able to take an 18g dose.

Not necessarily.

To some degree, the puck thickness changes depending on the grinder and coffee. While I haven't done any tests, it appears to me that dark roasted coffees have thinner pucks than lighter roasted coffees (of course, this could also be a side effect of the types of coffees popular for dark roasts).

Back to your nickel test - in my experience long ago with the Rancilio Silvia, it wasn't forgiving of low clearance. Knowing this, one trick is intentionally using an oversized basket (e.g., 22 grams and dose 18 grams). I know that VST baskets have a reputation for being fussy, especially if not dosed as designed, but sometimes compromises for the equipment combination in front of you are necessary.

#3: Post by **SandraF** » January 10th, 2022, 2:13 pm

Depending on the coffee it will expand, in varying degrees, once water touches it. Some coffee will expand different than others, so will change.

#4: Post by **cafeIKE** » January 10th, 2022, 7:11 pm

<soto voce>I wonder how much coffee has been wasted trying to use ??g in a ??g basket?</soto voce>

For the googleth time, there is no such thing as an XXg basket in isolation.

There are XXg baskets in combination with group, gasket, shower screen, grinder, coffee, pressure.

The nickel test is a taste meaningless starting point to determine the relative depth of a weight of coffee relative to the tamp pressure and other machinations applied.

Parm wrote:My shots are tasting okay

If you haven't, read these:
Espresso 101: How to Adjust Dose and Grind Setting by Taste
Mano Lite: A Short Guide to Dialing in Espresso SOs and Blends

Brew by the taste, not some marketing guy's weight guestimate based on likely nothing you brew or own

#5: Post by **spopinski** » January 10th, 2022, 9:36 pm

Silvia's group screen are deeper than most, not counting the extruded nut.

January 10th, 2022, 10:19 pm

This is the information I was hoping to find out. I'll take the earlier advice and potentially use a slightly larger basket for those high doses to work around the machine. I get that not all beans are the same and will fill baskets differently, but I still was surprised at the lack of headroom using a stock 18g dose. I'll try dosing 16-17g in my 18 VST and grab a 20g VST for my 18-19g doses.

#7: Post by **fufek** » January 11th, 2022, 2:57 am

spopinski wrote:Silvia's group screen are deeper than most, not counting the extruded nut.

We're talking Silvia Pro here, it doesn't have an extruded nut.

Cheers

#8: Post by **spopinski** » January 12th, 2022, 1:03 am

Ah the new beast, my bad.