SISC Senior Member Joined: 3 Mar 2013 Posts: 10 Location: Sullivans Island Expertise: I like coffee
Espresso: Mini Vivaldi II Grinder: Mazzer Mini
Posted Sat Apr 6, 2013, 1:24pm Subject: Re: Mini Vivaldi II Consistently Inconsistent
You grind both shots at the same time?
Adding enough beans for two shots is enough to have a small column of beans above the burrs. In effect, the grind setting is changed when doing so. For example, the is a noticeably different grind setting required to achieve the same shot when you are single dosing, or using a hopper full of beans. The column of beans above the burrs provide a little bit of weight which helps feed the beans into the burrs, AND, there is no "popcorning".
If you're adding the beans for both shots at the same time, this is the "issue". The first shots worth of beans are ground through with a second shots worth adding slight bit of weight to them, and preventing them from popcorning. Then, as the second shots worth of beans make their way into the burrs, they have nothing above them, which also allows them to popcorn. Effectively, the second shots worth of beans require a slightly finer grinder than the first shots worth. Which is why your first shot runs slow and your second runs fast.
Try adding only enough beans for one shot at a time. Also, I still suggest grinding 2-3grams and tossing them before you start prepping your shot, because as diligent as one tries to be, there is always slight amounts of grounds left in a grider.. andlike I said earlier, as little as .2grams can affect shot time. By doing the quick purge, and adding only the beans you need for one shot at a time, you will see perfect consistency shot to shot. Might need to be changed from the current grind setting to get the shot running right, but the consistency will be there. Then once you make any needed adjustments you'll be on point.
This is a great suggestion, and one that I will continue to employ.
Problem solved...er, no.
The point that folks are missing is that the MV II is a VOLUMETRIC DOSING machine. The volume in cup 2 is usually higher volume. See the OP.
If the volume of water dosed is the same for both shots, then where does the water go re:the first cup? If the volume in cup 2 is noticably higher in a large cup, then water retained in the portafilter (a smaller container) due to grinding would certainly be noticable.
This is why I have been skeptical of the several suggestions that relate to grinding. Grinding does not explain why a volumetric dosing machine yields higher volume in the second cup..
Jmanespresso Senior Member Joined: 18 Jan 2009 Posts: 2,151 Location: Westchester NY Expertise: I live coffee
Espresso: Alex Duetto II Grinder: Compak K10 - Vario Vac Pot: Yama-SY5/SY8/TCA5 Drip: V60, Beehouse, CCD Roaster: Hottop B
Posted Mon Apr 8, 2013, 7:11pm Subject: Re: Mini Vivaldi II Consistently Inconsistent
Its not as simple as the machine just gives you a set amount of water each time.
The shot volume will change, using the same volumetric button, if grind real fine, or real coarse. the machine won't just run longer or shorter and dispense the same overall shot volume.
SO if you set the volumetric button to give you two ounces of WATER, you wont get two ounces of espresso. Same the other way. IF you set it to give you 2 ounces of espresso at a certain flow rate, you wont neccesarily get two ounces of water when flushing the group. Im not really well versed in the overall workings and intricacies of a flowmeter, I just know that thats how the machine behaves. If you want a more detailed explantion of the flowmeter, I would give the tech department at Chris Coffee a call and have a chat with them. Those guys are espresso machine gurus.
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