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Does silicon turn bad over time?


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#1 Daniel Agustin

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Posted 28 August 2018 - 05:23 PM

Hi,

I've looked at a lot of threads that discuss how much, and when to apply silicon to the o-ring. Everyone seems to agree on not opening the housing after each dive, or every day after diving, unless strictly necessary (replace the battery, memory card, sandy environment). I've followed that advice since day one. However, it seems like, at this rate, the amount of silicon I have stocked will last longer than my lifetime. I have six sealed S&S o-ring-silicon kits, and so far in three years, I haven't gone through the first one. Does silicon turn bad? Is there a shelve-life? It's stored in my Pelican case with the rest of my gear, in my basement, so humidity and temperature shouldn't be a problem. Any advice?

Thank y'all.

Daniel



#2 Dunadin

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Posted 07 September 2018 - 11:08 AM

Depends a bit on the grease. Some are a mix of two or more components that can separate over time. That is usually an issue if you use grease to keep moisture out or for lubrication of machines. It is not a problem for O-rings since you only use a very small amount. If you leave the grease out in bright sunlight or areas with high ozone or other aggressive gases, you can degrade it to the extend that the products can degrade the O-rings. The most important part is that you use a grease that is formulated for the type of O-ring you have. The wrong grease will swell or embrittle the O-ring. The only other caution is to take the O-ring out of the groove if you don't use it for a while. All elastomers will set over time and provide less efficient sealing. That is a good time to inspect the O-ring for nicks or other damage.


Sergio Lucato
Canon 50D, Ikelite Housing, 2xDS-160


#3 bvanant

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Posted 08 September 2018 - 10:48 AM

Sergio is right but there are some caveats. First there is a big difference between silicone and silicon. Silicon is used to make computer chips, it is a semiconductor and is inside your camera not on the o-rings. Silicone grease is one type of lubricant for o-rings, but there are others. Some greases are specific to some o-rings, but there are a few greases that can be used on any kind of o-ring. These include the tribolube and christolube perfluouropolyethers (not silicone grease) and some versions of Krytox (there are thousands of versions). These will be useful for all types of o-rings from nitrile to fluorosiicones. One reason that many housing manufacturers use silicone o-rings is that silicone has very very low compression set; the o-rings do not take a set. Nitrile o-rings on the other hand do indeed take a set (I have a housing from Subal where the o-ring takes such a set that it leaks after three dives).  

All of the tribolubes and christolube do indeed separate a bit over time, smushing it back together is not hard.

 

Cheers

 

Bill


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#4 Kire70

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Posted 12 September 2018 - 12:28 PM

I've never had it go bad, but if it separates, best to just get new silicon as it is cheap. Peace



#5 davehicks

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Posted 12 September 2018 - 05:09 PM

I think we are talking pretty long time scales here.  I have Ikelite lube tubes that I got 10 or 15 years ago (still sealed) and they are just fine.  As long as it's clean it's going to be fine.

 

As for when to lube it varies from Never to Often.

 

Never: Camera housing backs mostly are "Static" compression o-rings.  The oring does not slide over any surface it just gets compressed.  Never lube these, never stretch them, in fact never handle them at all unless they are visibly dirty.  Lube is not needed here and will just attact grit.

 

Often: Ports usually slide into the housing or screw onto a dome, etc.  These are "Non-static" or "Active".  Then always need to be clean and lubricated so they don't twist or bunch up.  Keep them clean and lube them enough so they are always slippery.  Again, never stretch them.


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