Advice sought: Rancilio Silvia 'gusher' extractions

[nikko.the.scorpio]

Folks,

I've recently taken receipt of the below gear and am having some minor issues - would greatly welcome feedback or thoughts (my sincere thanks in advance):

Here's the critical info:

Espresso Machine: Rancilio Silvia V3 (bought ~2012 from DiBartoli) - in very good condition, new silicon group seal.
Basket: Stock Rancilio 40-100-102 basket
Grinder: Compak K3 Touch (has brand new burrs in it ~2kg or less through them!)
Tamp: CleanMachine/ProTamp 58mm
Coffee: CS sourced home roasted (within week of roasting)
Dose: 13-14g of grinds into basket

Problem:
Double shot extraction (have measured into labelled shot glasses) seems to consistantly come out far too rapidly. I have to terminate the shot at 10-15sec as it's clearly beginning to blonde badly. The resulting shot will be bitter (which thankfully is marginally hidden by drinking with milk BUT I know a lot better can be done). I reverse temp surf before I pull the shot, don't feel this is an issue in the problem.

Solutions already tried/thoughts:
GRIND..?
My first thought was that it was a 'grind size' issue. However, I'm at a VERY fine grindsize that I'd feel is closer to Turkish than traditional espresso size. The K3 is well regarded and as stated has brand new burrs in it, which I've checked and definitely are correctly aligned. I've taken it all the way to choking the machine and then backing off a tad but it's such a finely balanced point I feel this isn't the issue.

I've compared my grind size to a fellow CSer who has a La Spaz S1 Vivaldi II with a HG1 grinder and he's using a much coarser grind than myself (big difference). If it assists see below macro images of my grind with table salt etc for comparison. So if anything at present I feel my grind might be a bit finer than ideal for long term usage.



DOSE...?
With these stock 'improved' Rancilio baskets the common feedback is that a ~12g grind dose is pushing things (others feel this way?). So I've found that ~13g is about as much as I can put. When tamped (and I tend to err on the side of a lighter tamp) it bring it down to just under the internal ridge line. I'd previously had some issues with distribution but try and stir the grinds with a thin bamboo skewer and take my time in prepping the basket for the shot.

I've also got a couple of 17g La Mazocco ridged baskets, which I've bought as they were sold as being 'identical to VST baskets' though thats clearly NOT true. I know using a larger basket is often felt to assist with the Silvia's but if I can't extract properly from the stock basket I can't imagine a different one will magically cure it as there's likely other variables at play.

PRESSURE/FLOW..?
I secretly suspect this might be the issue as I've read several other threads of folks in an identical situation and often it was their OPV at a high level. The machine was originally bought from a CS sponsor, Di Bartoli - but when I contacted them today they weren't able to advise if the machine would have been calibrated prior to shipping out - as I wasn't the original purchaser and it was ~3yrs ago.

In a very inexact flow test I got 101g of water out through the portafilter in a 15sec extraction. Now apparently if you want to test the pump/OPV flow you're meant to use a blind filter and then measure the flow via the overflow tube instead....?
http://coffeesnobs.com.au/brewing-eq...out-gauge.html

Happy to try this as I suspect mine is running high so if folks can confirm this is safe to do. I should also flag that I live in a regional area with no CS sponsor etc nearby, nor access to a pressure gauge so perhaps this is the best way to check the OPV is not running far too high.

Thank you in advance for any feedback or assistance,

Nick

[Bazooka]

Hi Nick, if your pour started tight and then followed by gusher, it may be worthwhile checking the puck for channeling and how level it is

Good luck

[nikko.the.scorpio]

Hi Nick, if your pour started tight and then followed by gusher, it may be worthwhile checking the puck for channeling and how level it is

Good luck

Bazooka, much thanks for the reply.

Apologies in advance but by tight shot I'm not sure if you mean it came only from the centre of the puck (which as I don't have a naked PF I don't think I'd be able to verify) or that it takes a lengthy-ish period from hitting the extraction button to the first liquid coming through?

As I do get a little of the latter but unsure if thats the core reason......what I mean by this is that I'm sure my dosing and tamp technique isn't bang on (if anything I'm sure I tend to stuff around with it too much wanting to get it perfect). I'm very careful NOT to tap/bang the grinds once I've distributed them with a skewer or finger - and obviously particularly careful after tamping, which as stated I tend to try and do towards the soft end of the scale.

Getting the tamp level has also been a bit of an issue, which is part of the reason why I'm leaning towards softer tamps as when I was trying for the 15kg effort I'd end up having a lean on them despite my best efforts to avoid this.

Again I feel these are factors as I'm a million miles from being perfect in my approach but I'm unsure if they're the root cause of the gushers. But it's excellent you flagged them as they have been real issues I'm still working with. :-)

[Bazooka]

Hi Nick, If your shot started as slow drip, followed by trickle, and then gushing, it could be due to channelling. Water under pressure is a cheeky creature, it tries its darn hardest to find a path of least resistance, so if your ground distribution is not uniform and tamp not level, your shot may be more susceptible to channelling which you see as gushing.

I hope this helps.

[cleanCup]

Could your beans be the issue ?

[Chrisj1984]

Have you tried grinding finer and tamping a bit harder. I usually tamp pretty hard. Dosing i just fill the basket, firm tap on bench and then put more coffee in and distribute coffee evenly around basket and level off. Then firm tamp

[JWILL]

Im finding odd results with my different aged diy roasted beans, 15/18vst precision 14 g can be better
Is the roas a problem, I have Variable consistency in my roasting process, a cast iron pot and ozito hg on the bbq if the temp curve/rise it is done wrong I have had trouble getting good shots

Is less than a week long enough for or the beans the beans to sit??

Just my 2c from hours of reading and 6m experience correct me if im wrong,
v3 pid silvia and sm90

Edit: I do get better results weighing exat spec on scales for basket 14/15/18g in paper cup dosing from there helps with distribution as well

[kyeba]

which as stated I tend to try and do towards the soft end of the scale.

Getting the tamp level has also been a bit of an issue, which is part of the reason why I'm leaning towards softer tamps as when I was trying for the 15kg effort I'd end up having a lean on them despite my best efforts to avoid this.

I think you should keep the same consistent tamp pressure of 13-15kg so you're not guessing so much with one variable. Also try 2 of these tamping techniques which will make getting a level tamp easier.

[nikko.the.scorpio]

Much thanks for all the great replies and feedback - I REALLY do appreciate it.

@bazooka, much thanks - I'll pay a bit more attention next time around. From what I recall from this morning's two extractions, I made the grind just a smidge finer and tamped firmly, however I had to cut both extractions off within the 15sec mark as they had started blonding, only getting around 30ml of actual end extraction (after the crema had settled down). I do tend to get a slow trickle at first but this is gone very quickly and it really gushes - hence the very premature end to the extraction with way under the ~50ml I believe I should be getting from an espresso double shot.

Your advice on channeling is duly noted and I'll incorporate some of the improved tamping techniques provided to try and negate this.

@cleancup, the beans are not the issue. CS sourced and roasted by me within the last week and I've been roasting for a significant period and have no issues with this area. :-)

@Chrisj1984, as shown in the images provided (and I ground even finer today) I'm already grinding at the finer end of the scale and MUCH finer than others on quality espresso machines. So I hear what you're saying but thats more a remedy for the disease than an actual root cure to the problem. As I suspect the issue is either the OPV or issues with channeling from my tamp/dist method - possibly a bit of both.

And I suspect it's a bit the same with tamping harder, as if there's issues with those two thiings tamping harder will just alleviate part of the problem but bring different issues into play. So I know in the short term I could go down the path of just using the finest possible grind that will work, regardless of how much it's getting closer to the Turkish/flour end of the spectrum and tamping very hard but surely IF I can locate the actual problem it'd be easier and give better end results to fix that first.....but I just need to see if the flow is an issue (***again other than a pressure gauged PF does anyone have some definitive info on how to do the flow test on the Silvia V3?***) or my tamp etc, this being the logical one to eliminate/improve first.

@kyeba , ah thats excellent! That first image is a gem and very handy - I was using a different technique - which even from looking at that I can instantly tell was vastly inferior so I will give you suggestion a try from here on! Much thanks.

(***again other than a pressure gauged PF does anyone have some definitive info on how to do the flow test on the Silvia V3?***

[kyeba]

however I had to cut both extractions off within the 15sec mark as they had started blonding

Are you still using the small rancilio baskets? I'd give the 17g LM basket a go, try filling it, tapping your group handle once(or twice to get a bit more) then filling it again and level off, tamp then pull a shot and see how long you get out of a shot before it blonds. If it pours too slow or fast, adjust the grind accordingly. I say this as I notice quicker blonding with lower doses in my Silvia too, especially when trying for a 50-60ml shot, so I up dose to compensate.

[Bazooka]

Good luck Nick, in my experience, grinding too fine may actually increase channeling risk and hence gushing, perhaps this is due to water under pressure getting desperate and less forgiving to non uniform distribution and tamping

kyeba pics are very good reference for tamping, next time you tamp, try leaving the tamper in the basket and check levelness, i found i put more pressure on my thumb when tamping and had since adjusted my technique

[nikko.the.scorpio]

@kyeba, Great reply much thanks! Yes, I've been hanging in with the 'improved' Rancilio 14g basket. Ok - I'll try the LM 17g then. Will try exactly as you state, as it's a double basket I'll aim to fill to rim once leveled and then tamp.

@bazooka, again another great reply, much thanks! Interesting point RE: grind - I just know that as I've gone finer and finer it's not really helping and I feel thats not the variable thats the issue. I also find that the much finer grind is more of a PITA to distribute evenly as it's more prone to clumping etc. I'd like to back the grind off to where I feel it should roughly be and then try and work with the tamp technique and dose. If neither of those assist then I guess I'm looking at the OPV being at too high a pressure.

I know I keep coming back to this last one but the very common feedback is that Rancilio tended to always set their machines too high ~11.5 to 10.5 bar. I'm very dubious about whether DiBartoli calibrated this machine prior to it's sale as it was a mail order buy by the original owner and when I spoke to them they took a very long time in checking only to say they no longer adjust them as they've found the V4's run at 9.5bar from the factory but they couldn't advise what they did before this.

Anyway it's a theory thats on the backburner as improving the tamp/distro will assist regardless - I'll try the LM baskets (need to give them a polish inside with some high grit wet&dry as pucks do not fall out easily).

Thanks again for the great feedback.

[Javaphile]

Nikko, have you thought about renting the traveling pressure gauge?


Java "Always nice to know the numbers" phile

[nikko.the.scorpio]

Nikko, have you thought about renting the traveling pressure gauge?


Java "Always nice to know the numbers" phile

Hi Javaphile,

I have - and if I get to the point where I've eliminated all other variables and want to exclude the OPV then personally I'd see the ~total cost of getting a go with it, which will end up being $30-35 as less attractive than buying one from a forum sponsor for ~$90. Personal call but I feel the cost is a tad high to make it feasible.

That said, I'd probably try the backflow reading first to see if it's in the appropriate ballpark - if NOT then I'd fine tune/adjust via the gauge. :-)

[nikko.the.scorpio]

Ok - as per earlier advice I went back and tried with the LM 17g baskets (I hadn't been overly impressed with these on my first couple of uses of them). Backed the grind off a very small amount (as I felt it was getting waaaaaay too fine and not assisting). 19g of grinds were placed in the basket.

Dosed to the rim and distributed with a skewer, tamped using Kyeba's recommended technique (which gave a nice level tamp) - did a hard tamp that was easily 15kg. Again at around 12sec I had to terminate as it'd run it's course volume wise (~55-60ml in end volume). Quite bitter though I couldn't see obvious blondeing in the extraction.

There was no dribbling that progressed straight to the gushing - rather within a few seconds of anything appearing at all you're getting a far too strong flow of extraction.

I know puckology is apparently regarded as next to useless but I think a few things might be able to be seen from the macro shot I took of the basket a few mins after I got over cursing the bad extraction:


1. There's no signs of channeling I could detect, there's a few lil marks on the edge on the left but thats nothing at all and goes nowhere.
2. The basket was overdosed, as shown by the shower screen indent on the puck - I'd say 17g would be about the limit (I placed in 19g).

I can also advise that the LM baskets are almost impossible to get the pucks out from.....every time I've used them they stick in there like they're glued in place!!! Really tough to get out - and I have to end up digging out with a spoon, which I hate to do as I fear damaging the base. Anyway I'd have thought if channeling they'd be a lot easier to remove.

Anyway I felt that the tamp, dose (if anything overly high but still made no difference) and grind were pretty much on the mark and yet there was no real change in the result. I don't know if in itself says that the OPV is looking more the likely suspect or if I'm convincing myself of it.