At our cafe we use a 3 group linea and have always left spent coffee pucks in the portafilter between brewing to maintain temprature in the group.  This is something we have done for quite sometime.  Recently we have been having problems with our group screens warping and spitting water out the side.  One person i have talked to thinks the two are related.  Does anyone else leave the spent coffee in the portafilter between shots or has anyone had problems with their screens?

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what i have been told is that the screws are designed to stop before you can over tighten them.
Ah, I'm sure that's the case. I'm starting to say stuff I know very, very little about 

Garrett M Esary said:
what i have been told is that the screws are designed to stop before you can over tighten them.

Might be true for some machines, but I own/use a NS Aurelia and this certainly isn't the case with it. Once the screwhead goes flush with the screen I could easily turn the screw another 1/2 turn or so, which will surely lead to distortion of the screen. As soon as it's flush I stop as it will slowly tighten a bit during use anyway.

 


Garrett M Esary said:

what i have been told is that the screws are designed to stop before you can over tighten them.

Good point, Shadow... the custom screw design used on La Marzoccos is different than any other I've seen. Most other screws can easily be over-tightened with bad consequences.

 

Before anyone suggests that this point is misplaced in a discussion about Lineas, lets remember that lots of people will read discussions like these and assume that the information also applies to their machines. Glad you jumped in to make that point clear.


Shadow said:

Might be true for some machines, but I own/use a NS Aurelia and this certainly isn't the case with it. Once the screwhead goes flush with the screen I could easily turn the screw another 1/2 turn or so, which will surely lead to distortion of the screen. As soon as it's flush I stop as it will slowly tighten a bit during use anyway.

 


Garrett M Esary said:

what i have been told is that the screws are designed to stop before you can over tighten them.

You might also want to put a scace on your group head if your screens are warping prematurely, which seems to be your main problem. If you are running hotter than is needed, that could be a cause. Of course, if you reduce the temperature even a little you will need to take into account that the espresso will extract differently.

 

As for over tightening of the screws, it is entirely possible if you are using a screw driver to place screens back in the machine. You should be able to use fingers to reinsert, and only go finger tight. This will probably answer your heat question as well, or at least give you some indicator.

Garrett,

 

Could you be overfilling the basket and smashing the screens with the tamped puck?

Screen warp: you could be dosing too much espresso into the portafilter.

Water spitting: could be the overdosing as well and/OR well as worn gaskets.

If there's too much espresso, the portafilter cannot seal properly to the gasket.

 

Check your dose quantities and then adjust the grind as necessary to taste.

Do you run preventative maintenance on your machine or do you have a technician come in and do that for you? If you're left to do this yourself, you might want to unscrew the screen, remove it, look at the backside with all the holes (like a shower screen) and see if it's clogged. If the holes are caked with dry and solid espresso oils you may have found the problem. You can clean it out with a pin or anything narrow enough to pick it out. Just be careful not to poke a hole in the screen. This could take a while but is well worth it. If the screen is warped and needs replacing it would be a good idea to clean the new one at least once a month or so to stay on top of this. In my experiences, backflushing will only do so much, especially if your baristas have a habit of leaving full portafilters in the group head (which allows the grinds enough time to cook on the screen and ensure future clogging. How often do you backflush the group heads? And yeah, it's always a good idea to check on your gaskets whenever you get water leaking out the sides. 

Hello Garrett,

 

I immediately dispose of the puck. Maybe these are paranoid reasons.


Try an experiment: Leave a spent puck in. Pull a shot. Drink it. I don't think it will taste good. Even if you clean the portafilter between shots, are you cleaning the group head every time? How? Flushing, scrubbing and wiping? That could be a lot of work. The longer coffee is in contact with something like a portafilter, the darker it becomes, accumulating old oils that don't taste better then fresh coffee. Technically you can season a pumppot or a portafilter, but knowing how old coffee tastes, do you really want to?

 

1. Coffee oils and coffee grinds sitting up against the group head, cooking against the screens and gaskets can become a maintenance issue as you are finding out. You will have to replace the screens and gaskets more frequently. Look at your screens through the light. Are they clear? Are they free of debris, but have an off color? If so, put the screen face down in a steaming pitcher. Gently place the steam tip where the dispersion screw would be and begin steam, past the point that milk should be steamed. After you are done, look at the water to see how much coffee grinds come out, the more rumbling in the pitcher while you are steaming, and the hotter the water the better. Despite the use of cleaners, the coffee grinds find their way into everything and won't go away. The Joe Glo and Puro caff work great against the oils, not the grinds. 

2. The old coffee oils taste rancid. Fresh and clean group heads, screens and baskets. You are not losing much temperature without the puck. Pull a portafilter out that has been sitting in the group head for awhile. It's hot. The flavor is in the cup. The boiler is hot. The group head is hot. The portafilter is hot. Need it hotter? Add hot water from the hot boiler.

3. For a few degrees of temp lost by not having a puck inside is easily recooped by flushing the group head for a few seconds. Leave your portafilters in the group head for sure, but keep them clean. The cleaner the equipment is the better chance for great coffee.

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