Ahoy folks. I was inspired to replace my piston seals to fix my channeling problem on my cremina because of this thread about the cremina grouphead temperature study Olympia Cremina Temperature Study, Part 2.
Tekomino found some useful numbers for the bell, but he was using a new cremina. When I tried to recreate them, my grouphead was overheating after the first shot. It was hard to get the grouphead down to 180 (2-3 cold water portafilter switches) and very hard to get it below that. Even at 180 (around the hottest it can be to pull a nice shot), by the time I dosed and tamped, the group would get to 185 before I could pull.
So, the big difference between the older and new creminas is that the new ones have a thermal break between the boiler and the group. Orphan sells this, but I'm not sure if it fits the older models. So I ordered a 6x6" piece of 1/8" teflon, cut it round and drilled 5 holes (4 for the bolts, and a 5th for the water tube). Installed, it is just small enough to accommodate the bolts. The group is now stabilizing at 169 as opposed to 203. So i'd say that it's a success. I thought other cremina users might like to know this. Also, this might apply to Pavoni owners as well, and all other leverheads.

Where did you buy the teflon piece?

Good thinking.

Partial temperature control solution for Elektra Microcasa

John

I'd also be interested in a source for small quantities of "virgin" (rather than "mechanical") grade PTFE/Teflon. I've got some steam-valve seals I need to fabricate and don't trust the stuff in the surplus yard to be "food-safe."

I ordered the piece from Amazon. Warning, it's very hard to cut, you you will need a drill and at least a box cutter. JMC, you're route was probably smarter so that you could add and remove them. I figured 1/8" I could double if I needed to, but I was totally wrong. 1/8" is just about the max I think, and I'm lucky that it turned out to give the correct temperature for me.
Today I pulled 3 shots. The group takes a bit longer to heat, but I can give it two pumps (without flushing) to bring it up to temp quickly. After a shot I rinse the pf under cold water (like i normally do to get the grinds out of it, and lock it back into place. The group is good to go around 3-5 minutes after that.
PTFE/Teflon is a bit suspect. I know about 350-500F it is awful stuff, but I couldn't find anything saying that it was bad below that or that it shouldn't be in contact with water. Do you, Jeff, know something I don't? I'd like to use some virgin also. One awesome thing about teflon is that you don't need any gaskets (although I left mine in) since teflon is itself a gasket; although it's fairly rigid at 1/8".

Nice work John. Is there any noticable flex in the group during the pull?

bostonbuzz wrote:II know about 350-500F it is awful stuff, but I couldn't find anything saying that it was bad below that or that it shouldn't be in contact with water.

And just a warning, overheated teflon releases poisonous gases, unhealthy for humans, but fatal for parrots even in small quantities.

And just a warning, overheated teflon releases poisonous gases, unhealthy for humans, but fatal for parrots even in small quantities.

If your coffee machine gets up into the dangerous heat zone for Teflon then I think it would probably start to melt.

Is there any noticable flex in the group during the pull?

None that I can detect. I did the same to my Aurora lever ( now owned by drdregs ) and on neither machine have I been able to detect a downside.
The only reason I haven't done my Cremina is time and laziness.

I get gaskets etc made up pretty regularly so if people are interested I can get a quote on them.

John

jmc wrote:If your coffee machine gets up into the dangerous heat zone for Teflon then I think it would probably start to melt.

True, and while it isn't exactly on topic for espresso machines, people here *do* roast, and roasting can easily climb into the danger zone for teflon. Needless to say, don't use teflon in a roaster.