What is white stuff betwee thermostats and boiler?


New member
Jun 14, 2005
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While removing the failed heating element in my Saeco (Estro 410) espresso machine for replacement, I noticed a white (creamy and caulk like) substance between the two thermostats and the boiler body. It is not corrosion and it was certainly applied during manufacture, as I am the orginal owner of this machine and have not taken it apart previously. I guess that it was applied to improve the heat conductivity between the thermostats and boiler body, so that they operate at the correct temperatures. However, I am not sure.

Most of this white substance came off or was spread around during disasembly of the machine and there is much less of it now between the thermostats and the boiler body. My questions are these:

1) What is this white stuff and what is it's purpose?
2) Do I need to apply more of this substance (or a substitute) to the thermostats for my machine to work properly?
3) If yes, where can I get this white substance (or substitute)?

Thanks for any info on this subject.


New member
Dec 3, 2006
Jacksonville, Fl
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Hi hkeiner; This is nice that I can contribute something on my first post. You are correct about its function. Its called thermal grease, and its normally silicone based. Its jb is precisely as you guessed. It helps to transfer heat from one surface to another by eliminating air gaps between surfaces. I'm an electronics tech by trade and we use it in all mounting high-power transistors to heat sinks.

Its available at places like Radio Shack and most any electronics store. Use it sparingly and spread it thin.