stefano65 wrote:the traditional looking one they have a 1.8 calibration...

Some of the espresso machines I've tested included the factory inspection sticker showing it passed pressurization. They're not as high as you might think - only 2.0 bar, if I remember correctly. Personally I would sleep better knowing it's idling well below the factory pressure test:

Boiler level probes. These probes tend to be pretty generic, just a steel rod with an angle at the top for the level box connection. They are usually cut to length for the boiler. I would not worry that the probe is completely inserted into the boiler since it was probably trimmed to a specific length for that boiler. With all the steam talk, I was thinking about playing with the water level as a possible fix. More water = higher pressure but less volume, lower level get you more volume but with less pressure. The key is matching the volume, heating element and steam tip to provide sustained steam.

Dave, I'd point to Ian's analysis:

cafeIKE wrote:Steam production and foaming milk successfully rely on several interelated factors.

It's the velocity of the steam that produces the foam.
The velocity of the foam is related to the hole diameter, steam volume and pressure.

More water, i.e. higher level will produce more steam when the pressure is released. The potential volume of steam is directly related to the water volume and temperature above the local boiling point at the boiler pressure. The down side of a high water level is the initial volume of steam is reduced and the pressure drops more rapidly when the valve is opened, reducing velocity.

The capacity to continually produce steam is related to the heat input, the input water temperature and the pstat setting. The water level has no effect. Water level affects how quickly the system can recover once the valve is closed.

The water level probe can be adjusted by loosening the small upper nut slightly and pulling up on the probe.

cannonfodder wrote:[...]With all the steam talk, I was thinking about playing with the water level as a possible fix. More water = higher pressure but less volume, lower level get you more volume but with less pressure.

More volume = higher pressure? The discussion reminded me of some of the saturation physics. The equation would not be true, I think, but am not 100.000% sure the water/steam are in saturated condition as per physics definitions.
I would say, more water creates more heat inertia so you suffer less from incoming cold water and the effect of losing steam maybe even. Losing steam however has serious cooling effect and must be compensated by switching on the steam heater a.s.a.p. In this sense, pressurestat deadband may be part of the equation.
Less water would mean more (saturated) water damp, at least initially.

cannonfodder wrote:[...]The key is matching the volume, heating element and steam tip to provide sustained steam.

From Ian's analysis I became aware of another aspect of the steam tip. Personally I never steam, so I have to discover these things, reading around. Most discussions I read on steam tips seem to focus on nr, size and angle of the holes. In fact, most of that discussion is an optimization problem that will differ per machine and where the discussion implicitly is about (flow) speed of the steam. The question then is if less holes or smaller holes in the steam tip could still maintain flow/speed of the steam, even when passing less quantity and what the effect would be on the time needed to heat the same amount of milk.

As to the VBM DB, part of the "not enough steam" discussion should then focus on nr of holes and diameter.

Having seen the photos and this debate, I would want to insulate that steam boiler btw. Being small, its surface area relative to its contents is larger than would be the case with a larger boiler. If it really would extend the steam life of the boiler is still to be seen though.

HB wrote:Some of the espresso machines I've tested included the factory inspection sticker showing it passed pressurization. They're not as high as you might think - only 2.0 bar, if I remember correctly. Personally I would sleep better knowing it's idling well below the factory pressure test: [youtube movie]

I am sure the leading people in these fora are aware of this and most certainly Dan/HB, but what you see in the movie is supposed not to happen with your espresso boiler because it has an over-pressure valve (OPV). The experiment in the movie requires the OPV to either be sealed (made dysfunctional) or replaced by a permanent cap. It seems to me the boiler was prepared for the experiment as you can see one of the end plates has nicely come off for it to behave like a steam driven rocket.
In your espresso machine, if the OPV is opened, I wonder if it would close again when the pressure drops. I would expect it needs replacement, in which case you need to stay away from the maximum pressure it was designed to open at.

Regards
Peter
Netherlands
Europe

CafSuperCharged wrote:Dave, I'd point to Ian's analysis:

I believe that is what I said. More water gives you more pressure but less volume of steam so it goes flat fast. Less water gives you more steam but at a lower velocity.

CafSuperCharged wrote:In your espresso machine, if the OPV is opened, I wonder if it would close again when the pressure drops. I would expect it needs replacement, in which case you need to stay away from the maximum pressure it was designed to open at.

Yes, they will reset. The valves are spring loaded, think OPV on steroids. When the pressure gets above a point, the piston compresses the spring and opens the release valve, venting the excess pressure. When the pressure drops back down the spring/piston closes, unless it is caked with scale then it may stick.

Edit, a clarification. When I say on steroids, I am referring to the physical size. The boiler valve tends to be physically larger than the OPV, although VBM uses a larger than average OPV. The OPV opens at a higher pressure than the boiler pressure release valve, but they have the same base principal. A spring loaded valve that opens at a given pressure.

I'm having a heck of a time with my new DoubleDomo.

Bottom line, very light colored Crema from a coffee that I know when brewed properly produces medium->dark crema.

I think I need a scale to dose out 14g and see what that looks like from the way I dose now, but my dosing method worked on my Adreja Premium.. I suppose that doesn't really matter with the new Machine.

Maybe some VBM Super owners know if the VBM is really sensitive to dose... I think this is part of my problem... And I'm sure pictures would help, but I'm picture-defunct right now.

After brewing you can clearly see the brewhead screen imprint on the puck. This leads me to believe I'm overdosing, likely to a detrimental extent, and then all other bets are off. I've visually dramatically reduced my dose, to the point where before distribution/tamp coffee doesn't even come to the top of the portafilter (the mound in the middle is higher, but not by much, which makes it difficult to get 'even' distribution). Even at this "low" a dose I see the screen imprint on the freshly brewed puck, loud and clear.

I have the PID set to 107 right now, and I believe my display is in Celsius as it only goes to 130. I'm assuming a 205f brewtemp is about right, and I'm trying to error on the side of darker anyway, thus the 107... But crema is very, very blonde, even with a shot cut short at 23sec, and even on my over-tamped 12bar 40second or so shot.

"Slightly frustrated"

What kind of beans are you using, how old are they. I am assuming they are not old subpar beans. Light Crema could be channeling or low brew temperature, provided it is not the beans. If you are overdosing too much and the puck is scraping the shower screen when you lock it in you may be causing cracks in the puck and channeling. I am assuming the DoubleDomo and the Domabar Super use the same group, 14-15 grams should not be a problem. If you are getting a shower screen imprint before the shot (tamp, lock in and then remove it) then you are putting in way more than 14 grams, probably more like 18-20. If you have a light imprint on the puck after the shot but not before, that is OK. The puck swells during the shot and will often lightly touch the shower screen.

If you don't have a scale, and it does not sound like you do, you may want to start there just to confirm your dose. You will need one that has one tenth accuracy. A one gram scale won't do much good since it can be off by half a gram or more.

Someone correct me if I am wrong, but 107 Celsius is 224.6 Fahrenheit, a little hot for espresso. I believe I read that there was a 7-10 degree drop between the boiler and brew group. Split the difference, say 208 in boiler for 200 at the group, you would need a PID setting of 97.7 Celsius. You may want to try turning down the PID a bit.

Beans from barefoot, roasted on 4/18... And a bean I've used a lot and like... Quite doubtful it's the bean.

Temp: My converted says 205F=96.1C. I just doublechecked with this site: http://www.wbuf.noaa.gov/tempfc.htm and it says the same. So I added 10, and then +1'd it because I was trying to get darker crema, nothing more.

I'll lock and unlock a freshly tamped puck and see what it looks like. I suspect this is a problem, but I hope I'm wrong. It seems reasonable to me to dose a heap of coffee in the PF, level off, and tamp, shouldn't produce a puck that "massacres" the showerscreen when locked in. Otherwise it seems difficult to level off any sort of dose of coffee. No tapping or any other way to overdose is being used, just heaped on there, leveled off, and tamped.

Scale needed. Maybe I'll go get one today, just to erase this as a variable.

A level sweep across the basket should get you in the 16-17 gram range if I remember correctly, and again provided the basket/portafilter/group is the same as the Domobar Super which I believe it is. When working on headspace, I will put a nickel atop the finished puck, lock in and then remove. If the nickel is mashed into the coffee, I dose down more. I did a blurb about it when working on the bench article for the Domobar Super and single baskets.

buzzmc wrote:. . . and even on my over-tamped 12bar 40second or so shot.

Somebody (your dealer) should have set your machine up with a Scace II Thermofilter such that it produces a 200 F, 1.75 to 2.00 ounce shot with 9.0 bar at the portafilter. They could even have included a nice, hand written, thank you note saying that "This is how we set your machine up BUT feel free to play around from here. And, oh, by the way, here's how you do that . . .

If your brew pressure gage is hitting 12 bar, something's wrong - as far as I'm concerned. The "regular" Vibiemme is pretty stable from a temperature standpoint:

erics wrote:Somebody (your dealer) should have set your machine up with a Scace II Thermofilter such that it produces a 200 F, 1.75 to 2.00 ounce shot with 9.0 bar at the portafilter. They could even have included a nice, hand written, thank you note saying that "This is how we set your machine up BUT feel free to play around from here. And, oh, by the way, here's how you do that . . .

If your brew pressure gage is hitting 12 bar, something's wrong - as far as I'm concerned. The "regular" Vibiemme is pretty stable from a temperature standpoint:
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I see a {small} business opportunity here... which, if someone in the bay area has said Scace/etc, which I assume can't be cheap, and wants to help dial in my machine, I'm sure we can work something out... Part of the reason I bought this machine was to stop worrying about some of these things.