Grouphead Cooling on the lever machines

[mbach]

I posted earlier an idea for grouphead cooling (a radiator type device at the head gasket) but after considerable thought and pulling 5-8 shots a day on my LP-Pro, I feel like a good solution might be a blank portafilter with some sort of super-cooling substance in it, or made of copper and shaped with vanes on it. Seems to me a copper/brass blank portafilter put into place while preparing the next shot might cool things off enough. I've heard of folks icing down the neck between, but if a portaradiator ( ) would work, that'd be cool.
meb

[cannonfodder]

The problem is not necessarily the portafilter. The temperature problem comes from an overheated group head, which is why some folks use the iced towel over the grouphead trick.

[mbach]

Yes, yes exactly. What I'm saying is: Pull a shot, remove pf, replace with device inserted where pf was which cools grouphead more rapidly than just waiting, Clean PF, fill w/ coffee, remove cooling pf, replace and pull another shot.

[timo888]

I posted earlier an idea for grouphead cooling (a radiator type device at the head gasket) but after considerable thought and pulling 5-8 shots a day on my LP-Pro, I feel like a good solution might be a blank portafilter with some sort of super-cooling substance in it, or made of copper and shaped with vanes on it. Seems to me a copper/brass blank portafilter put into place while preparing the next shot might cool things off enough. I've heard of folks icing down the neck between, but if a portaradiator ( ) would work, that'd be cool.
meb

I'm no metallurgist, but couldn't a supercooled PF-like device stress the metal? If you don't like the mess of the cold wet dishrag approach, how about an ice-cube tray where the ice is not shaped like a cube but is puck-shaped to fit the portafilter? Then could could pop a cube into the PF, lock the PF into the group, and when the ice is melted, pull another shot.

Regards
Timo

[MarkJ]

If you unscrew the spout at the bottom of the Pavoni portafilter, there is just a regular threaded end. I've thought of getting a plug for it--something like an acorn nut, and then putting an ice cube in there.

As is, I fill it with cold water and seal the bottom with my finger--this way you can achieve the 'portafilter wiggle' cleaning technique which otherwise you can't do with a lever machine.

You can even pull the lever up partway and suck cold water in the group for faster cooling!

[Linz]

MarkJ has the idea.

Here's my method - it's messy (but what isn't, with a Pavoni?) and it seems to help...

Find a small plastic bottle about 80-100mm diameter (is that 2-3 inches?) and cut off the bottom so it's a short, round vessel. You can also use a wide cup.

Then what I do, after each pull, is remove the PF and knock it out, fill the vessel, cup, or whatever to the top with cold water, hold it up under the open group head so it's immersed, and hoist the lever about 3/4 of the way up. Not all the way, or you'll be taking an early shower. Wait a few seconds then lower the cup and pull the lever back down. Out comes the water that was sucked up, but now it's hot, the group head is cooler, and co-incidentally the water's cleaned out much of the coffee crud that gets in there. If you want cooler, do it again.

I can't say I've tested this extensively but on the odd occasion when I've needed to pull more than my usual 1 or 2, it seems to have done the trick.

I'd be keen to hear of anyone else's experiences, I have too many coffee-phobic friends, and not enough espresso nutters like me, to really find out how well it works.

[Javier]

MarkJ and Linz,

As is, I fill it with cold water and seal the bottom with my finger--this way you can achieve the 'portafilter wiggle' cleaning technique which otherwise you can't do with a lever machine. You can even pull the lever up partway and suck cold water in the group for faster cooling!

Then what I do, after each pull, is remove the PF and knock it out, fill the vessel, cup, or whatever to the top with cold water, hold it up under the open group head so it's immersed, and hoist the lever about 3/4 of the way up. Not all the way, or you'll be taking an early shower. Wait a few seconds then lower the cup and pull the lever back down. Out comes the water that was sucked up, but now it's hot, the group head is cooler, and co-incidentally the water's cleaned out much of the coffee crud that gets in there. If you want cooler, do it again.

These are very clever and useful tips! With my Gaggia Factory, I usually don't notice any over-heating issues until at least the fourth shot ("cappuccino worthy"), so I am going to start practicing the tips indicated above.

Thanks!

Javier
Woodbridge, VA

[Linz]

I usually don't notice any over-heating issues until at least the fourth shot ("cappuccino worthy"), so I am going to start practicing the tips indicated above.

Like I said, it's messy. The problem on my la Pavoni is to hold something up under the head while holding the front of the machine down, while raising the lever. Three hands are useful here. I don't know if your Gaggia has the same 'lightweight base' problem. You can still practice after one cup without actually pulling another shot, just feel how hot the group is.

[fac10]

Newbie here, but reading this thread gave me an idea. I just pulled an Ace bandage cold compress wrap out of the freezer and wrapped it around the grouphead and neck. It has velcro closures so it can be wrapped around and left in place. I have little experience comparing methods besides the wet towel approach, but it seems to me that this has the advantages of requiring minimal effort and being not at all messy. The frozen gel starts out much colder than cold water, so it can absorb more heat than a wet towel. On the downside, the conductivity is low compared to other methods, so it doesn't work as fast. It seems this would be a good technique to use if you don't mind waiting 10 minutes or so and you have other things you would rather be doing than fussing with the machine. Conductivity would probably be improved by taking the gel pack out of the cloth bandage wrap, which is less convenient but perhaps it could be held in place with a rubber band.

[timo888]

Conductivity would probably be improved by taking the gel pack out of the cloth bandage wrap, which is less convenient but perhaps it could be held in place with a rubber band.

It is wrapped in plastic, isn't it?

Regards
Timo

[fac10]

It is wrapped in plastic, isn't it?

This is what I used.

The cloth bandage has a pouch that contains a gel pack sealed in plastic. The gel pack can be removed from the cloth, which would eliminate the undesired insulating effect of the cloth. You then need some way to hold the gel pack in place, such as a rubber band, self adhesive bandage wrap, etc. The plastic provides some insulation from the gel inside, so I think it will never be as conductive as a cold wet dishtowel, but it has the advantage of absorbing more heat in one pass, as opposed to the towel which requires multiple cycles of heating and then rinsing out again in more cold water. In my one experiment this morning, even with the cloth cover on, after about 10 minutes the grouphead had cooled from burn-your-hand hot to comfortably warm.

These things come in a variety of sizes and shapes, so there may be others more suitable for the task -- I just used what I had on hand in the freezer. If you really wanted to go to town, I suppose you could even custom design something in the exact shape you want to fit the contours of the machine.

[timo888]

I mean, wouldn't the plastic melt onto the group?

[fac10]

I mean, wouldn't the plastic melt onto the group?

I just tried it and the plastic did not melt. I will continue to experiment to see whether this technique has any real merit. I just ordered an inexpensive IR thermometer so I'll be able to measure the grouphead surface temp before each shot, to get a better idea of how the grouphead temp correlates to shot taste, and thus how much cooling is necessary to get back into the ideal range for good shots.

I should add that I am really only starting with my new (used) Factory, and still have to get past some more fundamental issues before I give a lot of attention to temperature concerns. Right now my shots are coming way too fast with very little pressure on the lever. No crema to speak of. I think the problem is worn out burrs, as I'm grinding on the finest possible setting of my Maestro Plus, and I see no obvious sign of channeling in the puck, and I'm tamping pretty hard. I have new burrs on order, and am hoping that will help.

[lino]

I just ordered an inexpensive IR thermometer so I'll be able to measure the grouphead surface temp before each shot, to get a better idea of how the grouphead temp correlates to shot taste, and thus how much cooling is necessary to get back into the ideal range for good shots.

Keep in mind while using an IR thermometer on your chrome group the numbers will very inaccurate. Measurements *may* be comparable to each other, that is, you may be able to tell if one cooling method works better than another, but the values given by they thermometer will be significantly off.

The reason is that most IR thermometers are calibrated to measure the temperature of a specific color (typically flat black, particularly on cheap ones) and the further are from that color, the larger the temperature error. Shiny white or silver is the "opposite side" of the emissivity color spectrum that IR thermometers measure, so the error will be highest on a chrome-like finish.

That said, some IR thermometers can be adjusted for color calibration, and others have sections in their manual describing ways to deal with this issue.


That said, give things a try and see what kind of info you're getting.

ciao

lino

[timo888]

I should add that I am really only starting with my new (used) Factory, and still have to get past some more fundamental issues before I give a lot of attention to temperature concerns. Right now my shots are coming way too fast with very little pressure on the lever. No crema to speak of. I think the problem is worn out burrs, as I'm grinding on the finest possible setting of my Maestro Plus, and I see no obvious sign of channeling in the puck, and I'm tamping pretty hard. I have new burrs on order, and am hoping that will help.

First, how fresh is your coffee?

Second, it may seem counterintuitive, but try tamping very lightly. Just enough to provide a level surface with approximately 1/4 inch headroom at the top. You might be getting side-channeling, or the channels might not be visible on the surface. Heavy tamping can exacerbate problems caused by unevenness in the distribution; a light tamp can ameliorate them.

If your shots are still too rapid after that, try increasing the dose while still tamping lightly.

Give your puck ~10 seconds to preinfuse, and then pull the shot. If you don't see a few drops coming out of the spout a few seconds after you have raised the lever all the way, then slowly and gently pull it down till a few drops appear in the cup, and when they do, ease up on the lever pressure and count off the preinfusion, then pull the shot steadily and with gradually increasing moderate firmness until you are pleased with the flow.

If the shots are still too quick after the above, it could very well be the grinder. But it doesn't hurt to get a sense of what happens at opposite ends of the tamp/dose spectrum (especially when your grinder is already at its finest setting).


Regards
Timo

[fac10]

Timo: thanks for the suggestions. I will give them a try.

lino: I have no experience with IR thermometers, so thanks for the heads up. The model I have ordered can be set for an emissivity from .01 to 1.0 so there is some adjustment possible. One web site I found that discussed this issue suggested using black tape on shiny surfaces to get an accurate reading at the default emissivity setting (0.95), then to adjust the emissivity setting until the same reading is achieved on a shiny spot. It also occurs to me that drawing a spot on the chrome with a black dry-erase marker might achieve the same objective. Sounds like a good way to spend a few hours some rainy afternoon. I'll report back with my findings in case anyone else here has an interest in this topic.

[Jarno]

Hi, I have read with interest about the problem with the la Pavoni group head over heating. I was wondering if any has tried or would think that interposting an insulating material such as a carbon fiber plate between the boiler and group head would work. I should resist heating, but would it be stiff enough to resist compression when pulling on the lever?

Thanks in advance,

Jarno

[timo888]

Actually, mogogear mused about an insulating gasket and stainless steel fasteners to address a similar issue on the Cremina, which is likewise a personal machine optimized for a few espressos in a row before the group needs to be cooled. It is something worth exploring, but for me, the material would also have to be safe for potable water applications in a high-temperature setting, and be able to stand up to steam for a long time. The Olympia factory has a simple recommendation: run the portafilter under cold water to keep the group cool.

Regards
Timo