TimEggers wrote:To follow-up:

I pushed my brew pressure up until the espresso started to get grainy in body and slowly backed it down until the grittyness went away (7.2-bar or so). The body is smooth creamy and the shots taste sweet and full flavored (not under extracted).

Tim, this was a GREAT tip. I have been getting grainy and gritty espresso out of my Silvia for a long time, and I thought the cause was in my roasting and choice of beans. Tonight I took my Silvia OPV valve apart, cleaned it, and modified the OPV setting with a little shim which should have brought down my brew pressure. What a difference! I pulled about 6 shots - every one was sweeter and smoother than I can ever remember from this machine.

Now, I actually have no idea what my brew pressure is because I don't have a gage yet...but I think a gage is in order. Why do they calibrate the Silvia for 12 bar stock?

Could be anything really. I'm not that familiar with the OPVs in espresso machines, but a lot of mechanical regulators show a bit of drift when they wear in. This isn't actually a problem if you are aware of it, and if it stops drifting after it has worn in.

Then again, the Silvia is a low-end machine, so most of the money you pay for them goes into materials, not quality control, so you really can't expect much of the QC. Some manufacturers just do a functionality check, and this might just be along the lines of "make sure if squirts water and steam when it's supposed to", and then they might not even bother checking controllers and gauges for accuracy.

vanboom wrote:Now, I actually have no idea what my brew pressure is because I don't have a gage yet...but I think a gage is in order. Why do they calibrate the Silvia for 12 bar stock?

Van,

Some numbers like 11 get floated around, BUT (and yes that was a big but) there is almost nothing easier to measure on a machine with a few plumbing parts.

Gauge ~20$
Various pipe fittings maybe another 20$.
Tearing your machine apart and understanding how it works... (well this is not a tv commercial) you know.

*Licking my cup after my morning cappuccino. This morning's shots turned out very good. I need to take Silvia's top off today and make sure the plastic shim I put on the OPV isn't melting from the heat. Some observations...

Shot Volume:
Before I made the mod, I had trouble pulling 2oz shots in 25 seconds. I could pull ristretto's OK, but grinding more coarsely to get 2oz of volume would leave me with channeling and early blonding every time. I was starting to believe that 2oz in 25s was an impossible target with this machine. With the lower brew pressure, I am able to run a 25 second pull and get 2oz with nothing but syrupy crema coming out the entire time with blonding starting around 23s-25s. Yay!

Channeling:
I would get spritzers near the end of my shot every time - I guess as the coffee was brewed out of the puck, the puck would get weak and start channeling. This was very disappointing to see perfect flow coming from the naked PF up to about 18s then spritzing and early blonding. After modding the OPV, I am no longer getting the early blonding and channeling.

Taste:
Most importantly, my shots taste smoother. I used to taste a gritty smoky taste no matter how light or dark my roast. I thought this effect was caused by my amateur roasting techniques but now my shots are much smoother and are without that smoky gritty tasting effect. The first 1/3 of my shot tastes nuttier and smoother and more like an eaten coffee bean, the middle 1/3 is sweeter. And once again I can enjoy a straight shot!!

I can't wait to have some friends over and get some more taste buds on this change. My advice to anyone with a Silvia: if you are struggling with channeling, spritzing, 3oz shots in 15s, 1.3oz shots in 28s, you might want to check your brew pressure. V3 Silvia has an adjustable OPV, older models require shim washers to change the compression of the OPV spring.

That is, of course, if you first own a good espresso grinder and are working with nice, fresh coffee.

I measured the inside diameter of the Silvia OPV copper washer to be 17mm. So I was able to find a thin red fiber washer at a local "old style" hardware store. They are about 1/2 the thickness of the stock copper washer and they are heat tolerant. So I tried one, two, three fiber washers pulling shots and decided that one extra fiber washer gave me the best shots.

What is odd, contrary to what I have read elsewhere - I was getting sour shots with very low brew pressures vs. shots that tasted over-extracted. Also, some very odd "gurgling" was happening with the steam switch turned on as the steam pressure was being relieved through the OPV. This only happened when I added 2 fiber washers (the width of a 2nd stock copper washer), which is probably a sign that the OPV is set to relieve pressure at TOO LOW of a threshold.