another diagnostic question: if you pull another shot or two in succession after the first, do they get hotter? if so, it may be that you need a longer warmup period. if not, then maybe a pressurestat adjustment or replacement issue.

my second, third, and fourth shots get progressively hotter (bane of existence/source of romance for the LP).

cbxl wrote:Re 18kg of pressure: Do you mean the pressure I apply to the handle when pulling, or the pressure I apply to the tamper when tamping?

I was talking about pressure on the handle - this corresponds to roughly 9 bars of pressure at the puck. Of course, the pressure you apply is totally up to you (and your arm strength) but what I meant was if you apply 18kg (40lbs) of pressure on the handle and it takes 30 seconds to complete your pour, you will definitely be within the correct parameters for espresso.

cbxl wrote:Re timing the steam wand: What temperature should the water before I start steaming? This seems like a good and useful test if I have some comparison figures.

Unfortunately I can't be of much assistance here - I used to own an older model Pavoni so any numbers I can give you do not bear much resemblance to your machine. Maybe do the test with tap water, state your starting and ending temperatures and volume used, and hopefully someone on the forum can try a similar test

mayhew wrote:He actually recommends vinegar for Pavoni's as an excellent descaling agent, as there's no aluminium in the machine to pit.

Could a chemist please weigh in on the risk of verdigris formation when using vinegar with brass boilers?

http://www.simplehousekeeping.com...tID=148&Art_Type=1

Regards
Timo

timo888 wrote:Could a chemist please weigh in on the risk of verdigris formation when using vinegar with brass boilers?

Hi Timo,

I'm a chemist, though admittedly not a boiler expert, but I'll give this a whirl. The first thing is that I believe they plate the boiler interiors on these machines with nickel to avoid the sort of brass corrosion you're talking about. If there were a little bit of exposed brass, the copper salts would be pretty soluble in the descaling solution, so I'd expect they'd just get poured out with the rest of the dissolved scale. I *would* avoid running any acid through the group and portafilter though, since it's bad for the gaskets and the often fair amount of exposed brass there.

In terms of the different acid options, the main role of the descaler is to dissolve salts from hard water like calcium carbonate, and since vinegar (acetic) and citric acids have very similar acidities, they ought to work more or less equally well. There may be some cases where the citrate helps dissolve certain salts better than the acetate, but I wouldn't expect that to be true in general. I suspect preferences for citric acid come mostly from the fact that it doesn't smell/taste as bad if any residual compound sticks around.

cheers,

Jake

FWIW I use vinegar once a month, maybe more. In the boiler and soaking the PF, basket and screen. I've had zero verdigris on any of these parts. It's a pretty distinct problem. Think "Statue of Liberty".

Oddly, the two places I *do* seem to have it are on the bolts for steaming head and the upper sight gasket, both of which are above the waterline and therefore above the vinegar I use. I've got some durogol on the way which I plan to use and really soak those two areas in.

At Brad's suggestion, I ground finer. As fine as my Gaggia MDF can go, then I tamped quite hard. There was noticeably more resistance at the lever. This was an improvement. The espresso came out somewhat hotter--in the low 150s in the cup--but still not hot enough. Still sour, but less so. This was preceded by a PF flush and a good warm up time.

I tried another shot. Unfortunately, the second wasn't better--oddly, it was actually cooler than the first and more sour. High 140s. This appears to be the opposite of most people's experience, so now I'm really baffled.

I also tried the steam wand test. Here are the results. I'd be grateful if anyone can interpret these figures for me.

Protocol: A cold start in a cool (64 F) kitchen. Boiler filled to 1cm below sight glass tube top with cold water (47 F in the tank). Steam wand closed. PF empty, but on.

From the switch-on, it took 7 min, 54 sec for the green light to go out. (N.B., I have a European 230V model, which may heat differently--i.e., faster--than the American 120V. This might affect boiler warm-up time, but I can't see how it would affect the steam-test time.)

I opened the wand for 10 sec to bleed "false pressure"; first some water came out, but by 10 seconds the wand was delivering just steam.

I closed the wand. The green light had come back on. As soon as it went off (just a few seconds), I steamed a 1-cup glass Pyrex filled with 8 oz of water at 67 F. (Technique: I inserted the wand into the cup below the water level and opened the knob all the way.) Measured from the opening of the knob, it took 52 secs for the water to reach 165 F.

In other news, I did also find that weird tamper-resistant Torx bit, so I got the bottom off. Here's a picture of the insides, plus a picture of the grooved-wheel thingy that I presume is the pressure stat.




What, visually, would indicate a problem?

And if I wanted to try to make the water hotter, what should I do to it?

Many thanks yet again, and happy New Year.

This isn't quite what you're looking for, but...

LP Euro' boiler with sight glass full with 68F water.
Switch on to off time: 7:28
Open steam wand to back off:8:38

One Pyrex cup filled with 8oz at 64F heated to 40C:1:03 (instantaneous temp)

I have a hunch that a small part of your problem is the really cold water you're using. I often have some problems with my machine if I start it in the morning* which I don't have if I use it in the afternoon.

You did find the pressure stat and it appears to be at the factory setting. (They must put that white stripe on it to give a reference point). I have no idea which direction to turn it in to increase or decrease the pressure.

I suppose something to try might be warmer water. How is the water temp so different than room temp?

I still say pressure stat.

the "white strip" is Loctite, or somesuch. it prevents the grooved ring from being screwed in (clockwise to compress the little brass ears), or backed off to raise or lower the p-stat pressure cutoff, respectively.

LP starting doing this awhile back, apparently, so we couldn't adjust the p-stat. hrumph.

if you do wish to adjust it, remove the p-stat first (twin wrenches to remove the p-stat fitting...i recommend a digital picture of the electrics first), carefully carve away the loctite with a knife/scalpel/x-acto knife, and then you can turn the ring (though it remains very hard to do so, even with the loctite off).

your machine looks pristine. i have a hard time believing that the p-stat needs adjusting, but hey--what do I know. maybe it's faulty. wish I could help more.

check this thread too, if you didn't see it already:

http://www.home-barista.com/forum...n-pavoni-t907.html

FWIW I don't think you need to remove the p-stat to adjust it. There's plenty of room in there to get your fingers in.

I was able to turn my p-stat pretty freely although I've read elsewhere that's not always the case.

I found the p-stat fitting a bit hard to envision. The bolt on the p-stat doesn't do anything, it's just there to give you a surface to stabilize the fitting with. The bolt on the pipe side is the one that turns. Hold the pstat still and turn the other bolt to loosen the whole mechanism.

If it were me, I'd remove the base from the boiler and then remove the pipe and p-stat from the wiring. Brass is pretty fragile and that will minimize the amount of torque you can put on the tube.

But, as I said at the start, to adjust the p-stat I don't think you need to do anything but turn the knob.