Quite rich and sweet at first, but there is a kind of lasting harsh after-taste to the coffee

From the video, I would expect that. It looks like you are getting some channeling. Around second 22, you see the barber pole, twister cone of death which is caused by a spot of higher flow (channeling).

You are also getting the donut extraction, where the shot starts at the perimeter of the basket and works to the center. The center flow is also slow to form which is why you have three streams in the beginning. They are dancing around the dead spot in the center. All tell tell signs of distribution issues. I documented similar results in the Dialing in a new espresso machine, a step by step guide.

Here's a short little article that Schomer wrote about the effect of high altitude on espresso and his own experience with such:

(PDF File)
http://www.espressovivace.com/arc...lucidcafe/LC15.pdf

BTW, he had no solution for the problem!

bc

DC wrote:...curious extractions with my Silvia...during extractions I often get an air bubble in the center of the extraction which forms underneath the main cone, and eventually causes the cone to twist off to one side.

DC, I also use a Silvia and have had much more consistent success since a) getting a goood grinder and b) installing a PID. The PID, of course, probably won't make a lick of a difference in the 'bubble-cone' effect, but I was thinking about what you'd written regarding the taste, esp. the bitterness after the initial sweetness. It looked like the shot went blonde just before the barber pole showed up and, in my shots, blonde = bitter. I also get accentuated bitterness if the water's too hot.

A surprising point for me was taking the temp of the water as it exits the grouphead and adjusting the PID based on that. I've seen/read that the usual PID temp setting is in the 225-229F range. If I did that, I'd get 220F water coming out of the grouphead. I dialed the PID down to 212F and ran a TC probe right up to the screen---and got consistent 199-200F readings. I suspect this relatively low PID:TC reading is due to my habit of flushing the grouphead at least twice as the machine warms up--a habit I developed when I first got the Silvia. At this temp (and with a rather fine ristretto grind) I get really sweet espresso with none of the bitterness. I also stop the shot as soon as the blonding occurs, which often means I"m stopping it at 14-18 seconds...a definite barista foul, but the shots taste good with no bitterness, so I keep doing it. You could try what our high-altitude friends have done & reverse-surf a bit longer.

I'd be curious to know how your shots taste if you try grinding just a bit finer (looks pretty fine already, based upon the results in the video) and stopping earlier. Hopefully, they'll be one step closer to godshot...

cheers,
Paul

pauljolly65 wrote:DC, I also use a Silvia and have had much more consistent success since a) getting a goood grinder and b) installing a PID. The PID, of course, probably won't make a lick of a difference in the 'bubble-cone' effect, but I was thinking about what you'd written regarding the taste, esp. the bitterness after the initial sweetness. It looked like the shot went blonde just before the barber pole showed up and, in my shots, blonde = bitter. I also get accentuated bitterness if the water's too hot.....I'd be curious to know how your shots taste if you try grinding just a bit finer (looks pretty fine already, based upon the results in the video) and stopping earlier. Hopefully, they'll be one step closer to godshot...

cheers,
Paul

Hi,

Nothing I've tried so far has had any effect on the twister cone. Some things I changed even made it worse, e.g. the shot starts with a twister bubble cone

My grinder is a Rocky, by the way. My tamper is 57mm, not a good fit, but got a 58 on the way. Using stock Rancilio double basket

Temperature doesn't seem to be a problem so far, at least taste-wise: i'm not getting sour shots and the coffee doesn't taste burned. I like my shots ristretto-range, so I am already at quite a fine grind.

In my experimentation so far, strictly changing one variable at a time and keeping notes, I've discovered that:
(1) My machine doesn't like being down-dosed, it yields soupy pucks and very bad channeling
(2) My grouphead is tilted at an angle (the showerscreen is level but the group is not, meaning that the pf locks in on a slight slant). The machine itself is dead level. Water exits showerscreen uniformly.
(3) To avoid an impression of the bolt in the dry puck, the basket needs less than 14g (as measured volumetrically by a spoon) of grounds - this means that at any higher dose the bolt is drilling a hole in the center of my puck, although there is no contact between puck and showerscreen - why didn't they just use a flat screw?

My standard technique, which worked fine on my old Briel machine - with the exception that it had to be slightly down-dosed - and which is giving the 'better' results on the Silvia: Grind into basket (without tapping) to a small mound, WDT, tap twice on the counter, then leveling NSEW with my finger (no pressure) before doing a staub tamp.

Alternative techniques I've tried are:

-WDT without tapping, and Mr. Brown's distribution technique from here. No obvious difference in pour.
-Modified stockfleths, NSEW leveling, followed by these:
-Gentle nutating tamp followed by normal tamp / just a standard tamp. All at a similar force. Staub tamping seemed to stop spray jets, no other obvious effect. None of them fixed donut extraction - guessing this could be a tamping technique/tamper size related issue.

The most common features of the extractions are as follows: Donut extractions, very flat cones until the twister cone in the center (which sometimes spins off to the left) always with a bubble, and dead spots around the center that do not heal up.

I'm fully aware that the problem here is me, and the extraction problems are all signs of bad technique. I'll keep practicing, but I'm burning through bags of beans with no appreciable improvement, so if any of you kind folk can see the error of my ways, I'd be grateful if you could help me.

Here's 2 pics of my spent puck from typical bad extractions (the bits of coffee round the edge are because i forgot to clean off the sides before locking it in, but this has not affected the pour), and one of the result in the cup






Dave

mrgnomer wrote:Could be the extraction too. That's one crazy cone. I didn't have a naked portafilter when I had a Silvia so I don't know what kind of cone I got with her but with the Vetrano I have now I rarely get a cone like that. My cones are small and centered and I find with a pull leaning towards ristretto the crema has more longevity and is almost elastic even if the over all volume is a bit short.

I'm still learning so I don't know for sure but I also tend towards low or underdosing so that could be the reason for short tight cones. The big cone and short crema might be tied to the dose level.

I like to get a nice large cone, but only on beans roasted more than 5 days ago. It's not unusual for me to get cones like that on 9 day old beans (Lekempti). I find it to be directly tied to dose and grind, especially grind. If the grind is too fine, then you won't get the large cone, and the dose in the PF has to be maximised (without hitting the screen), so that you avoid a really fine grind and can still maintain an extraction time of 1 oz in around the 23-28 second mark (for a single). Then and it seems only then, will you get that large bulging cone hanging down for 15 seconds or more.

DaveC

I have the same set up. Silvia and Rocky. My guess is that your grind/tamp is off, 38 sec is too much. The temp will not affect the timing to get your correct shot (2oz double) volume as much as the grind/tamp. As you know you are shooting for about 20 to 25 seconds from start of flow to get your shot volume, if it is taking 38 seconds you are grinding too fine or tamping too hard, probably the grind. Only other thing I can think of is the posibility that your Silvia pressure pump is off but that's not as likley.
Check your Rocky's zero point by running it while rotating the bean holder to a finer grind slowly until you can just hear a slight touch of the burrs, add about 7-8 units to that point and you should be in the ball park. My technique is to run a blank shot through Silvia to heat the portafilter and just turn on the boiler light then load, lock and extract 45 seconds after that seems to work good for me. In my experience bad shots are usually the result of being too hot vs not hot enough so if you error do it on the cool side.
Good Luck,
Ross