Silicone recommendation

[muttley000]

I am building a large plywood sump. The thread is here
I am planning 3/8" glass baffles and glass eurobraces. I am looking for a silicone recommendation as I will be counting on the baffles for part of the structural system for the tank. I don't expect much deflection without the baffles based on my research, but won't be ready for a water test for about 2 weeks to know for sure. So, what do you all think?

 

[uncleof6]

Wood + glass + silicone = no structural integrity. Glass + Glass + silicone = structural integrity.

Build wood channels for the glass baffles, use fiberglass, resin, whathaveyou to insure water damage does not occur, then use a neutral cure silicone to "seal" the baffles in the channels. The glass will not provide any structural strength. For structural strength, use like materials: e.g. wood, but silicone won't hold that together under pressure either.

 

[tallball158]

You can use any 100% pure silicon. Just make sure that it does not have any antimicrobial ingredients in it.

 

[uncleof6]

Silicon is an element. Silicone is an elastomer (polymer) containing carbon, hydrogen, oxygen, and silicon. 100% silicone indicates that the silicone in question does not contain co-polymers such as acrylic.

I have yet to find a single msds that indicates the presence of "antimicrobial" anything in it. There are two common types of silicone: acetoxy cure, and neutral cure. What everyone is afraid of, is simply a neutral cure silicone, such as Silicone II. Dow Corning 795 is also a neutral cure silicone, and is used extensively by public aquariums. What kills off tanks, is not some mystery ingredient, rather insufficient cure time. Insufficiently cured acetoxy cure silicone will kill off a tank also.

The issue here is acetoxy cure silicone sticks really well to glass, but not so well to other materials. Neutral cure silicone sticks well to "other materials" (metal in particular) but does not stick so well to glass. The OP needs to reassess what it is he is trying to do...he is wanting to use basically incompatible materials as far as silicone is concerned.

 

[ca1ore]

FWIW I built a number of plywood pressure vessels in the 90's. First one I built I held together with just silicone and it failed almost immediately even though I had painted all the faces and edges with epoxy paint which I assumed the silicone would adhere to sufficiently - it did not! Second one I built I screwed all the plywood panels together with wood screws and wood glue and then sealed all the inner corners with a bead of silicone. That did work, and the tank lasted for about 5 years before some grain splitting on the plywood face allowed water to started to seep through. But the silicone seals worked, but they played no structural role. I used a wood 'eurobrace' on this tank (also screwed and glued down); I don't think a glass one would work.

As long as internal glass baffles are not required for structural integrity, I think you could probably silicone them in and they'd hold. But they also might not

 

[muttley000]

The issue here is acetoxy cure silicone sticks really well to glass, but not so well to other materials. Neutral cure silicone sticks well to "other materials" (metal in particular) but does not stick so well to glass. The OP needs to reassess what it is he is trying to do...he is wanting to use basically incompatible materials as far as silicone is concerned.

Will roughing up the epoxy with sandpaper help this at all in your opinion?

 

[uncleof6]

Put simply and very clearly: don't silicone glass into a wood pressure vessel and expect it to be a structural member. Sealing with silicone is fine. Do not take it further than that.

 

[Stbobo]

when you do decide to use silicone.. Home Depot sells DAP aquarium silicone. Just an FYI!