Epoxy instead of silicone?

[Ryan F]

Maybe a dumb question but, why do we use silicone for binding glass tanks instead of epoxies? I frequently use epoxy for work and it forms a pretty strong clear bond. It is also hard so you could easily scrape and brush algae off without damaging it, it wont peel, and can flow into tight joints creating a water tight seal. I understand that some epoxies are not very dimensionally stable but the stuff we use as work is very dimensionally stable and that's one of it's selling points.

Not really planning anything with this info, just curious.

[lefty o]

my only concern would be the flexibility of the epoxy. the slightest flex could crack the epoxy or break its bond with the glass.

[CT_]

I think as lefty said having a slightly compliant joint is probably a good thing.  I don't know about the chemistry of epoxy, but PDMS (silicone) can actually form covalent bonds with glass, combined with the above and you may have a "tougher" joint. 

[gardenman]

I have a pet theory that with modern lasers you could fuse the glass together and eliminate adhesives completely. Isamu Miyamoto of the University of Osaka in Japan (along with Finnish researchers) has experimented with using lasers to weld glass.  Why not use a laser to more or less weld the glass together to make an aquarium? Doing so could radically reduce manufacturing time for aquariums and the whole process could likely be automated. You'd need a jig/fixture to hold the pieces of glass and then a robotic arm to guide the laser, but no curing time for the tanks. They'd go straight from the assembly line to shipment. No chance for leaking as they're essentially one piece of glass after the welding process. No ugly silicone seams. No need to ever reseal a tank. They'd be leakproof. 

[MJV Aquatics]

I'm a child of the 50's and look how far we've come. As a youngster I never would have dreamed that we could carry a computer, camera, and phone in a pocket! Laser welding glass seems like a great idea...after all, acrylic tanks don't use silicone.

[gardenman]

19 minutes ago, MJV Aquatics said:

I'm a child of the 50's and look how far we've come. As a youngster I never would have dreamed that we could carry a computer, camera, and phone in a pocket! Laser welding glass seems like a great idea...after all, acrylic tanks don't use silicone.

Same here. I was born in 58. The times have changed. My current smartphone is more powerful than the first five computers I owned. Lasers barely existed in 58 and cost a fortune, now I play with my cats with one that I bought for a couple of bucks. Welding together glass aquariums seems like a logical step forward. As you said acrylic aquariums are solvent welded together forming one complete unit. They're welding glass in labs now using lasers, so it should move from the labs to production lines fairly quickly. Given the volume of silicone that tank manufacturers consume the cost of the lasers should be able to be offset over the long term. Other than aquariums and architectural use, welding glass together has few commercial uses. 

[Ryan F]

Hadn't heard about glass welding. But I wonder how tanks are made now? Is it just some jigs and cheap labor or is there a robotic arm? If the former then it would be incredibly expensive to retool and result in tanks that were massively more expensive than today. If the later then you just swap the silicone injector for a laser and maybe some heaters and the cost may go down. Could work for acrylic tanks too. One production line that could handle both glass and acrylic tanks. Just push a button to change the lasers power.

[TheDukeAnumber1]

Not sure I would want a welded and effectively single piece glass aqrarium. Silicone seals and can micro deflect to relieve stress, vs welded glass mixing planes of rigidity and possibly thermal loads being a problem.

I would have to see it work to have confience it is a good idea.

And to the original topic, my life experience tells me epoxy is generally too rigid and would eventually will debond with the glass.