Internal overflow box (acrylic)

Burkette

New member
Ok guys, here's my question. I had a shop build me a 3/8" overflow internal overflow box (same as a CtC, but only a half version). I told them what I was going to be using it for, but somewhere along the line, the message was lost, and the builder flame polished the ends of the acrylic. So...I can no longer use silicone, as I was planning on doing, and now have to find another means to attach this box to the tank. I have an extremely serious glue that I know will bond to plastic and to glass, but the fumes are barely tolerable to me, so I don't even want to know what my fish will think about it. My other option right now is JB Weld. Only problem there is that the JB weld will be black(ish) and will be ugly. Do you guys have any other ideas on how to bond the box to the tank? I have been doing some research and it seems like some other type of Weld glue will work as wekk, but I want to make sure it will not crack the ends of the acrylic, like silicone will now. Thanks in advance.
J
 

leeit2me

Member
Are you gluing this to Acrylic overflow box to an acrylic tank or glass tank?? You can always lightly sand the flamed polish to get some adhesion. I have use Weld 33 (I think) when I need to glue some acrylic on my tank and it's pretty thick stuff and does fill in alot of gaps.
 

Acrylics

Active member
You can still silicone the overflow in, just use a neutral cure silicone rather than an acetoxy cure. My favorite silicones for acrylic are Dow Corning 795 and the GE 1200 series.

The only thing an acetoxy cure silicone might do is cause some crazing. If the material is cast, probably not that big of a deal. Still not recommended, but FYI :)

IMO do not sand the edges, a polished edge actually silicones much better than a sanded edge IME.

HTH,
James
 

Losungen

New member
I'd still silicone it. There also more more pressure on the outside of the overflow then in it. It shouldn't come lose on ya.
 

Burkette

New member
You can still silicone the overflow in, just use a neutral cure silicone rather than an acetoxy cure. My favorite silicones for acrylic are Dow Corning 795 and the GE 1200 series.

The only thing an acetoxy cure silicone might do is cause some crazing. If the material is cast, probably not that big of a deal. Still not recommended, but FYI :)

IMO do not sand the edges, a polished edge actually silicones much better than a sanded edge IME.

HTH,
James

See, and I asked the guy who actually fabricated the piece this very same question. He said that NO silicone was safe. I imagined that the reef safe silicones wouldnt craze the edges, but he flat out told me I was wrong. I'll try it out...hopefully it will work as planned. And I'll try and get some pictures up, even though my camera screen is broken. Thanks guys!
 

Acrylics

Active member
Just keep in mind that neutral cure silicones take much longer to cure than acetoxy cures do. I usually let mine sit at lest a week, preferably two weeks.

Your mfr was right in the sense that you don't want to use silicones for structural purposes, but you're using it as more of a pressure gasket that utilizes the adhesive qualities of silicone.

It's the acetic acid in acetoxy cures that can cause crazing. Neutral cures still outgas but not nearly as bad as acetoxy cures and the solvents are not nearly as concetrated.

HTH,
James
 

Burkette

New member
Just keep in mind that neutral cure silicones take much longer to cure than acetoxy cures do. I usually let mine sit at lest a week, preferably two weeks.

Your mfr was right in the sense that you don't want to use silicones for structural purposes, but you're using it as more of a pressure gasket that utilizes the adhesive qualities of silicone.

It's the acetic acid in acetoxy cures that can cause crazing. Neutral cures still outgas but not nearly as bad as acetoxy cures and the solvents are not nearly as concetrated.

HTH,
James
Wow! THat's qhute a long time. I guess that my tank will be ok with just some powerheads agitating the surface for a week. Do you have any other suggestions that might be a bit quicker for curing? Something that might do it in a couple days that wont craze the plastic? Again...Thanks a million for the help.
J
 

Acrylics

Active member
Not if you're going to use a neutral cure, they are just that way, patience :)
If you want to use an acetoxy cure, might craze, might not, but it will be faster.

James
 

Burkette

New member
Not if you're going to use a neutral cure, they are just that way, patience :)
If you want to use an acetoxy cure, might craze, might not, but it will be faster.

James
And the silicone will adhere to the glass and the acrylic? I just want to make sure that I dont invest a few weeks of down time in my tank, just to have it fall off as soon as I take the c-clamps off.
 

Volcano1

New member
Just did mine, let it stay clamped overnight and no problems.
If your using black acrylic and black silicone, I don't think youd notice any crazing.
I used the all glass black , and didn't notice it craze at all.
It does seem to have less of an odor than clear.
It stuck as good or better to the polished parts, as those that were a little rougher.
 

Acrylics

Active member
And the silicone will adhere to the glass and the acrylic? I just want to make sure that I dont invest a few weeks of down time in my tank, just to have it fall off as soon as I take the c-clamps off.
It works for me and I do it everyday :)

James
 

Burkette

New member
It works for me and I do it everyday :)

James

James, thanks a bunch for the help, one more question for you though. If I use a fast cure silicone, and it does craze, will there be a structural integrety issue? If there is some mimimal crazing, will it be ok? And if it will not be ok, can I sand the edges of the box that will be attached to the tank, and then use a fast cure silicone. I dont think that I'll be able to keep my tank out of commision for 2 weeks without all my fish and other stuff dying. So my options are:
Fast cure, no sanding, possible crazing
Fast cure, sanding, don't know if it will craze
natural cure, no need to sand, tank down for a week or two, possible fish dying.

I'm just trying to weigh the pros and cons of each method. I do not mind sanding the edges of the box if its neccessary, but need to know if it will work, and how heavily I need to sand it. Thank again. I'm learning as I go along.

Jayson
 

Acrylics

Active member
James, thanks a bunch for the help, one more question for you though. If I use a fast cure silicone, and it does craze, will there be a structural integrety issue? If there is some mimimal crazing, will it be ok? And if it will not be ok, can I sand the edges of the box that will be attached to the tank, and then use a fast cure silicone. I dont think that I'll be able to keep my tank out of commision for 2 weeks without all my fish and other stuff dying. So my options are:
Fast cure, no sanding, possible crazing
Fast cure, sanding, don't know if it will craze
natural cure, no need to sand, tank down for a week or two, possible fish dying.

I'm just trying to weigh the pros and cons of each method. I do not mind sanding the edges of the box if its neccessary, but need to know if it will work, and how heavily I need to sand it. Thank again. I'm learning as I go along.
As a generality, it won't be a problem so nothing I'd lose sleep over. Just wanted you to be aware :)
Don't bother sanding the edges, the stress is in the material well below the surface.

James
 
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