Silicone problem

[Corsec]

hey all,
trying to install baffles into a 55 gal sump. The baffles are plexi glass. I installed them using Clear Window and Door silicone from lowes. The silicone stuck great to the plexiglass but as soon as I filled up the tank to check for leaks the danged baffles floated right up. The silicone didn't even try to attach to the glass. It had dried for several days and I don't have a clue what happened, I have used this method in the past with good success. Any thoughts or suggestions?
thanks

 

[Abysswater]

bad silacone sealant.

 

[KevinM]

Or...more likely...dirty/oily glass?

Kev

 

[coralnut99]

The basic problem is that silicone doesn't adhere to acrylics (or plexi glass). The only way you can use it is if you silicone in thin strips of glass (preferably 1/4" glass) directly behind the acrylic (by behind, I mean the area behind the acrylic, so that it will rest on it, when there is water pressure on the acrylic), then silicone the acrylic in place. It won't be a watertight seal, but it doesn't have to be 100%, as long as your acrylic panels are a snug fit.

I've never bought the GE silicones, I get a pretty good price on AGA silicone at my LFS, so I don't have to think about what type I can use. You may very well have the wrong type of GE silicone as well, but others in this forum will know better than me. hth

 

[coralnut99]

woops! Just re-read your post, I had the adhesion backwards from what you experienced. I agree with KevinM's observation of some residue on the glass. Especially if it's sticking to the plexi, and not the glass. Did you buy the tank used?

 

[mcontemp]

When you started filling the tank did you start on one side only? Try filling each section of the baffles equally (and slowly) to eliminate the bending of each acrylic baffle. The silicone doesn't adhere to acrylic very well so this is a must, especially when working with glass and acrylic together.

Keep in mind you were working with a smaller tank before so you probably had no problems.

Try it again you should be fine.

 

[coralguy1]

I work with glass every day. I agree that there is probably a deposit on the glass. Try cleaning the glass with rubbing alcohol first. I have built many waterproof frog tanks using GE silicone II (silicone 2). This silicone should be fine for baffles, however, an actual aquarium silicone like Perfecto or All Glass will be much stronger. Beware of other brands you find at the hardware store. Some will turn to mush after being totally submerged for a year.

 

[Corsec]

Thank you all so much for the replies. After looking back I what I did I believe this was a case of me being stupid. It occured to me that I did this in my shop while wearing a sweatshirt. I am a very hot natured person so if it was cool enough for the sweatshirt I bet it was at least 50 or less. Would the low temp be a contributing factor? I had prepped the glass very well, it was clean and dry. I had heard about the problem with the acrylic not wanting to adhere very well. I had installed these baffles in a 55 and plumbed up the tank about 6 motnhs ago. The baffles worked great for several weeks while testing the plumbing etc.. When I was tearing down the tank to move it to my office for installation I knocked the end out of the 55, don't ask. So I now have a different tank that I am installing the baffles in. I cleaned everything up and move the tank indoors and reinstalled the baffles using a new tube of GE I clear. We'll see how this turns out. Thanks again for all the suggestions!