Agree with you to to some extent on the dubious character of coffee processing... yet I take it that a high temperature environment potentially draws out much more muck than washing etc...I try to buy organic beans when possible too.

Think that for now I'd rather replace a silicone o ring a bit sooner, though from what I think to recall is ptfe safe up until 240'C or thereabout, but silicone not much less...well thanks for the food for thought!

It is more than the temperature. Temperature is just 1 of several considerations for a given material suitability for a given application.

Francesco's ring is about 3.5 mm diameter, or so it said from the website best I can tell. that is very close to 1/8".

I found some PTFE/Carbon braided packing material for a high temperature steam valve, 1/8", and quite cheap on Amazon. Should do fine.

Thanks for the tips.

I found an interesting article on braided PTFE packing material: http://www.fluidsealing.com/sealingsense/may07.pdf

It is an interesting article. Valve packing is an art unto itself.

Color is not indicative of a specific o-ring material and the o-ring Francesco used may be one of several different materials.

My steam tap valve had been leaking very slightly, more an annoyance than anything. I dug around in my parts bin and found the two o-rings that came with the OE rebuild kit. Took the steam valve assembly apart, cleaned out the old packing, and discovered there was already a brass washer in there. So I just put the washer back in with one of the o-rings on the side close to the steam tap. Maybe ten minute job total with the clean out of the old material being the majority of the job. Brought her up to pressure, no leaks now.

I wouldn't worry too much about sourcing fibrous packing material. Just get the correct size (and material) o-ring and call it good.

Interesting. I have an OE Gaskets kit, but as many of you probably know, it's a bag of gaskets. Unless it's a clear one-for-one swap, I wouldn't know what was intended to go in the steam valve. One of those rings was placed there for the steam valve?

There are several o-rings in the OE kit. The 2 small rings are intended for the steam valve. The next size up is the one that spreads the rod seal (i did not use this). Then you have one for the sight glass and 2 different sizes for the piston where only one is to be used. Then you have the large boiler seal. That should cover the o-rings.

You then have two square cylinder to body seals, where you use one, the piston rod u-cup, the portafilter gasket and shim, and finally the gommino.

Thanks - I figured as I removed one, I would fine a new one that matched it in size and replace one-for-one. The steam valve ones would have thrown me. It is interesting how many of these restorations would simply not have taken place if it were not for forums like this, and a web that connects people from all over the world at light speed.