I've had my Oscar for 1.5yrs now. I've pulled the odd extremely tasty shot here and there but the signal to noise ratio was very low. For the last couple months I've been using the La Scala Butterfly that my work has and I hadn't even touched Oscar until yesterday. I've been able to pull consistent, shot after shot at work, each one wonderfully more drinkable than 99% of what I was creating at home. I was all ready to sell Oscar and upgrade to a traditional E61 HX. The Oscar is an HX but just not the big shiny e61 variety. Now in the past in order to try and increase my success with Oscar I'd adjusted the boiler temp, and adjusted the max brew pressure by way of installing a cold water opv, and tried to hone in on the ideal flush, pull, flush, pull routine to no avail. I have a good chunk of change invested in various liquid filled gauges and brass fittings. About the only thing I hadn't tried was rented the Scace, that was next. Well I may have finally figured Oscar out.. or at least what works for me. Last night after work I decided play around with the boiler temp again. I tried going even lower as that seems to be the trend among HB'ers. No dice. Ok, let's go the other direction and crank things up to about 22 psi or 1.5 bar. Bingo. Flush plus 150ml and tasty espresso! again, and again, and again! I think that because Oscar is a smaller HX with less thermal mass she is more prone to fluctuation. By increasing boiler temp she rebounds much quicker to a point where the flush gives repeatable results.

The other thing I did was give a proper clean to the dispersion screen. I'd done this before but hadn't really taken a good look in the light. Anyhow there was plenty of crud around the edges of the holes in the screen so I soaked it overnight and this solved the uneven extraction problems I was having as viewed with my naked PF. I have noticed that after cleaning the group gasket that removing the pf is really hard. Will this improve or can i season it with something?

nixter wrote:I think that because Oscar is a smaller HX with less thermal mass she is more prone to
fluctuation. By increasing boiler temp she rebounds much quicker to a point where the flush gives repeatable results.

Indeed, "dragon" HXs are easier to temperature surf, if you don't mind the extra long flush.

nixter wrote:I have noticed that after cleaning the group gasket that removing the pf is really hard. Will this improve or can i season it with something?

It may loosen up as coffee oils build up. Or, to state the obvious, you may be tightening it too much.

Just pulled another shot. Didn't lock the pf in very hard at all and it required some quick firm smacks to the handle to remove it afterwards. I think the problem is that I used a little spray cleaner in the group when I was cleaning it. Probably degreased the gasket too much. Would a little olive oil on the basket rim help or would that just burn?

Perhaps you are over dosing and the coffee is expanding and making it hard to remove the group?

Mark

nixter wrote:I think that because Oscar is a smaller HX with less thermal mass she is more prone to fluctuation. By increasing boiler temp she rebounds much quicker to a point where the flush gives repeatable results

Bad science, dude

Could be that since it's about 20°F hotter than a couple of months ago the inlet water is warmer and cools the machine less.

Without taking a series of measurements to profile the process, it's pure speculation.

Glad you're getting good espresso at home

I never made any scientific claims. The use of "I think" generally refers to speculation. I feel pretty confident in my theory though. Yes, inlet water as well as everything else gets warmer faster, providing a higher base temp from which to flush down from.

Quick question: how many seconds after the 'sputtering' does it take you to reach the 150ml? I am starting to get better consistency with 7 seconds after steam dance and no intentional recovery time (i.e. whatever it takes to lock and go or ~4 seconds). Thanks for the helpful information.

Just to update my situation... Things have improved even more in terms of taste and consistency. I haven't changed anything about the machine but I have made some slight adjustments to my prep and technique. First, as soon I buy a 1lb bag of beans and get it home I separate it into 4 small ziplocks and toss them in the freezer. When I'm running low I take one out at night and toss it in my VacuVin container for use the next morning. One ziplock lasts me about 3 days. Secondly, I have been doing 2 or 3 pre flushes in the 5 or so minutes leading up to my pull. I then do a final flush about 30 seconds out from shot time but I don't time it exactly. By this time the machine has been on for an hour so I feel the pre flushes are helping to stabilize the thermal mass. I'm sure with a scace I could get it down to 1 flush of X seconds but this is working nicely and so far hasn't required any exact timing.

Until this point I have strictly been using popular blends such as 49th Parallel's Epic or Itelli's BC. On Sunday I bought my first SO bag of Ethiopian Sidamo which I will be testing out tomorrow. I'm excited. I didn't want to start experimenting with other beans until I had some reasonable control of the other variables.