D4F Senior Member Joined: 15 Mar 2012 Posts: 1,676 Location: USA Expertise: I like coffee
Espresso: Gaggia Classic PID Grinder: Preciso
Posted Sat Jun 29, 2013, 8:18am Subject: Re: Sour shots, help!
IMO, a micro flush, just enough to make sure that there is no air in the boiler and that water is ready to flow is beneficial on a Gaggia. Do it after the boiler is hot, but then wait > 20 sec to let the boiler heat back up before doing the shot.
Be careful with any flush. You will run about 10cc/sec during a flush as the pump flow is unimpeded. To really purge air it is best done through the steam valve, highest point, and that purge can be done as you end a session if you do not have leaks, or at the beginning of the session. On Gaggia, I would not flush prior prior to a pull, plan ahead on flushes.
Hi brianl, all good suggestions. I have 10 bar static pressure and am using an espresso blend. The Mignon is a particularly clumpy grinder but I stir my grinds in a cup before dosing. The pour looks pretty even provided I prepare the puck carefully. I get spritz (or sprites?) all over the place if dose straight from the grinder.
D4F, I have been pulling 60Ė70ml (approximately) in 27Ė30 seconds (also approximate, as I use my wall clock). Iíll have some scales soon to measure my how much Iím dosing, but until now Iíve been filling the portafilter with enough coffee to smooth off the top and fill the edges before tamping.
I now have a digital thermometer reading boiler temps, following AndyPandaís instructions, and constructed a cheap thermofilter using a bottomless pf handle, an old 14g basket and a k-type thermocouple. Unfortunately I broke the thermocouple when I switched on the pump because the pressure blew it out of the basket. It was quite dramatic.†Iíll try again when the replacement thermocouple arrives, perhaps with some other way of fixing it in place.
I donít know how anybody whoíd lend me a decent grinder to test with, but I have cleaned my Mignon burrs with a brush just in case. If my next coffeeís a good one, Iíll have a job to tell which change made the difference.
Thanks for all your advice and discussion, Iíll update again tomorrow when I have water temps.
Good work, you have been busy. There is a lot of pressure to consider in making a thermofilter. JB Weld epoxy held up. You can do a lot with the digital thermometer and mentally take account of the offset you need to get good temperature in the cup.
Are you temperature surfing?
Adding steam/heat before the shot?
Try doubles at 30 - 50 mg so that you are not adding so much water to through the boiler, and I think better extraction ratio.
now that you mention 60-70ml. It has me wondering whether you're using enough coffee. Similar to D4F, I usually shoot around the 30ml mark with 18 grams of coffee and it's nice and thick (no sourness). if you're using less coffee and twice as much water, well, you know.
my other strong inclination is water temp, but D4F has you covered there.
... The Mignon is a particularly clumpy grinder but I stir my grinds in a cup before dosing. ... I donít know how anybody whoíd lend me a decent grinder to test with, but I have cleaned my Mignon burrs with a brush just in case ...
The Eureka Mignon is a highly capable stepless grinder that can compete with some commercial grinders. Very consistent. Don't worry about clumping. As you've probably experienced they dissolve easily upon distribution. I used to do the WDT myself, but I found out that tamping alone suffices as well. Channeling is no issue. YMMV
*** "This drink of the Satan is so delicious that it would be a shame to leave it to the infidels." (Pope Clement VIII on coffee)
Thatís good to hear. I really enjoy the Mignon but donít have much to compare to, just a couple of goes on a Mazzer Super Jolly and my previous grinder, which was a second hand Gaggia MM. Since experimenting with WDT Iíve noticed I only need to toss the grinds in a cup to remove the clumps.
General update: I cleaned the Mignon burrs yesterday. New coffee, precise scales and a new thermocouple arrived in the post today (easily the most exciting post Iíve had in a long time!). I just need some good epoxy glue to finish my thermofilter, then Iíll be fully at one with the fluctuations of the Gaggia. I have already pulled a shot with a boiler temp of 110įC (a conversion of AndyPandaís higher boiler temp), with the steam switch on for 4 seconds just before brewing. This is an arbitrary without any measurement of my own water temps, I know, but Iíd say the shot was actually closer than Iíve been before. Iím using different coffee though, so itís hard to tell where the improvement is coming from. Iíll report back later when I have a water temp reading.
On baskets:†I only have a single basket and an 18g VST. The double that came with the machine now has a hole in it for my thermofilter, so itís out of action. If I understand correctly, I should get a 14g basket so I can brew with less water? Enabling me to maintain more consistent temps through my shot?
Probably the most important part of temperature control to blunt the intrashot drop is the steam blip and rest of 3 - 4 seconds each before the pull. If you do not wire in the steam switch to add heat without changing the 3 way then be sure to warm up at least 15 minutes. AndyPanda flushed to start his method, but then continued to add heat via the steam switch as I add with the Alarm function of the PID.
The thermofilter will help you to see where you are, but the thermistor bead, or thermocouple, on the boiler will let you see where the boiler is and you can reproduce that temperature to reproduce the thermofilter temp.
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