Silicone changing over time?

[Ctwoodtick]

went up to check the top of my liner to see if mid season sweep was needed. It appears fine for now with some soot throughout liner, but top few inches having thin powers soot in small quantities, so seems good. While up there i noticed that some places where silicone was used, the silicone appeared brown and it seemed like there was less of it there than I recall seeing previously. My installer used silicone (not sure if it was high temp silicone or not) to seal where storm collar comes together. Storm collar surrounds my liner which then covered by a double flue metal cap. Installer put some silicone on the small bolts that hold the cap onto the screen of cap. He told me that the screws appeared a bit loose in general so he put a bit of silicone on each one so that the cap would not come loose.
Well, now there appears to be less silicone that sits atop the cap on those bolts than before and the silicone has taken on the color of brown soot (the color seems to make sense given that it could be discolored from the smoke out of chimney. I’m not sure what to make of how it looks like there is less silicone. Could this have burned off? The cap itself did not appear warped or anything like that. Have had no reason to suspect a chimney fire or significant overfire of anything. Put a couple pics up for the heck of it. Not sure if there is anyway to tell what, if anything, happened.

 

[zig]

Silicone doesn't last forever. Just clean the surfaces and put more on. Had to do mine a couple of times, no big deal.

 

[Ctwoodtick]

The install is only like 6 months old though.

 

[Hogwildz]

That's because he just blobbed it on there, and didn't work it in with his finger. I bet he didn't clean the factory oils off the metal first either.

 

[Rearscreen]

My buddy swears by this stuff called "Through The Roof!" I have no idea of the flammability.

 

[webby3650]

That's because he just blobbed it on there, and didn't work it in with his finger. I bet he didn't clean the factory oils off the metal first either.

You can’t be afraid to touch it! It won’t hurt you! Tooling it is a must.

 

[Rearscreen]

My friend and employer in the TV biz used Amazing Goop on almost everything. He'd tool it by licking his finger then shaping it as the glue wouldn't stick to the saliva. The end result wasn't good. I mean for him and his health.

 

[Hogwildz]

That's why you spit on your finger, not lick it.

 

[SteveKG]

I can testify that Through-the-roof is good stuff. However, I haven't used it in higher-temp settings and have no idea what is too high for it. I read a review of it in Fine Homebuilding Mag' when the product was put out on the market, glowing review at that. The longest spell I've had it in use is about ten years, so I will have to wait before claiming it remains as good as it is at first application.

As to silicone, when I built my greenhouse thirty years back, and about that time installed a bunch of skylights in the house, I used silicone sealant everywhere. Fifteen years or thereabouts later, I had to remove and replace all silicone. Big, big job on my 12 X 22 ft. greenhouse. There were areas I could pull off the bead of silicone with my fingers. Other places I had to cut it out with a razor blade.

I bought new silicone sealant from a sealant distributor and they told me that silicone, though advertised to be "fifty year" sealant, lasts nowhere near that long when exposed to harsh sunlight [and UV and weather]. When it was a newer product, they said, the "fifty year" thing was a guess due to how great the stuff was after a few years. [Removing the old sealant down to clean glass was a very arduous job, let me tell you.]

Plus, there are different grades of silicone. So...about all one can do is monitor the silicone as with any other sealant, replace as necessary, and use the top-grade variety when you do. The distributor advised that the silicone you buy at, say, a big-box store, is ok for general work but isn't near the top grade. [Of course, they like to sell top grade....] So far, the "better grade" silicone I bought to redo my greenhouse is holding up very well, no breaches.

As someone alluded to above, the surface must be very clean for silicone to really stick well. If a metal surface, I first clean it off with something like acetone or xylol. My impression is that the xylol worked a bit better for this, but I don't really have proof.