Siliconing glass baffles..

[Reefer2727]

Building my first sump and would like some advice as far as silicone and the baffles go.

Once I figure out where they need to go. Do I put silicone on the bottom and sides of the glass baffles before I put them in? Or do I place them in and then silicone them as they sit in place? Wha do people use to keep the baffles in place while applying silicone?

Also, when doing the three pieces beside each other for the bubble trap, is there a good technique used to silicone those tight areas that are hard to reach with the other baffles in the way?

My tank is a 75 with a 33 gallon sump. The sump is 36 L x 12 W x 18 H. The sump will be skimmer/ return / fuge in that order. My baffles between the skimmer and return (also bubble trap) will be 9" high. The baffle between the return and fuge will be 12".

Any help would be appreciated.

 

[rguyler]

I usually cut my baffles a little short to allow room for a silicon bead between the sump and baffle. a 1/4" total (allowing an 1/8" on each side) is fine. You want silicon inside the joint as well as skinned along the joint. This is the way glass tanks are assembled.

As for doing the deed, I glue in the middle baffle first. Apply to the baffle or the sump doesn't matter here. For the two outer baffles, the above is more important as you can only really access the outside of the baffle assuming something like a 1"gap between baffles. Just be sure to get silicon in the joint and then a smooth seam along the line of the joint. Once it cures it will be very strong.

 

[Sokretys]

the bond between the glass and silicone is surprisingly strong. for simple baffleing, siliconing one side will do.

for the two panels that will be retaining water in your skimmer chamber and your refugium chamber...have those siliconed on both sides.

be sure to put a platform under your skimmer to raise it up to optimal operational depth

 

[redfishsc]

When I built my sump (which is a very small sump) I went through the rigamarole of trying to get a full bead on both sides.


It was an utter waste of time, I could have simply just put a few little dapples of silicone here and there, they really don't need to be "glued, screwed, and tatooed" in place.

They don't even have to be water-tight, since the flow rate going through them will be way more than the tiny unsealed openings at the edges could allow to pass through.

 

[uncleof6]

Silicone inside the seam. This is the proper way to do it. Seams made properly do not need a bead on the outside of the seam. Take a look at a quality rimless tank: Silicone in the seam, not all over the place. Yeah it is a sump, so who cares about silicone all over the place. Agree, that middle first is easiest either way. And it takes NO extra effort to get water tight seams.

Jim

 

[mille239]

Click on my red house, and scroll through and see how I set my baffles in the sump to hold them while applying silicone. Very simple!

 

[46FiatYamaha]

I siliconed the middle first like most people, and for the outer baffles, I put silicone where the glass would be first, then put it in, smoothed the outside seam like normal and used a small (1/2") piece of PVC to smooth the inside of the seam, not that it matters that much anyway but it worked

 

[Kur]

There is no need to have extra space between your baffles and your sump walls. As long as even a thin layer of silicone gets between there, it will hold strong.

I've read tank builds where people try to leave 1/8 inch gaps between their glass and tank frame (plywood tanks) to be sure they 'have enough silicone'. Actually having that gap makes the bond weaker. Athicker bead isn't any stickier, or stronger. The silicone in between the two contacting surfaces isn't doing anything other than taking up space and allowing more room for flex and movement. Flex and movement eventually lead to fatigue failure, even in flexible silicone.

 

[BeanAnimal]

<a href=showthread.php?s=&postid=15129776#post15129776 target=_blank>Originally posted</a> by Sokretys
the bond between the glass and silicone is surprisingly strong. for simple baffleing, siliconing one side will do.

for the two panels that will be retaining water in your skimmer chamber and your refugium chamber...have those siliconed on both sides.

be sure to put a platform under your skimmer to raise it up to optimal operational depth

Actually silicone does not bond well to acrylic at all. When we silicone baffles inside of a sump, the acrylic gets embedded in the silicone that is stuck to the glass. Full embedment is what helps the baffles stay in place. As Uncle indicated, when performing a Glass to Glass bond, the thin layer of silicone sandwiched in the joint is what provides the strength. In a glass aquarium, the bead of silicone inside the tank offers protection for the joint and ensures it is water tight.

It should also be noted that not all "100% silicone sealant" is created equal. There are commercial and specialty products that are formulated to bond better under certain circumstances. There are a few silicone sealant products that have been tweaked to offer a better bond to acrylic.

The best recommendation is to use glass baffles for a glass sump

 

[BeanAnimal]

<a href=showthread.php?s=&postid=15144648#post15144648 target=_blank>Originally posted</a> by Kur
There is no need to have extra space between your baffles and your sump walls. As long as even a thin layer of silicone gets between there, it will hold strong.

I've read tank builds where people try to leave 1/8 inch gaps between their glass and tank frame (plywood tanks) to be sure they 'have enough silicone'. Actually having that gap makes the bond weaker. Athicker bead isn't any stickier, or stronger. The silicone in between the two contacting surfaces isn't doing anything other than taking up space and allowing more room for flex and movement. Flex and movement eventually lead to fatigue failure, even in flexible silicone.

Glass does not expand when exposed to water, acrylic does (it absorbs water). Some folks reason that a small gap should be left to allow for the swelling and prevent stress on the sump walls. In theory a thick piece of acrylic could put enough stress on a thin (say 10G) sump wall to cause failure.

In any case... Yes in most cases (especially a glass to glass bond) the thinner the silicone layer, the stronger the joint. On the other hand thinner joints are more prone to failure when used on a structure that is prone to flex or movement. The thicker layer of silicone acts as a buffer between the two moving parts. There is a reason that large tank builds incorporate thicker silicone joints. Large panels of glass and their supporting structures expand, contract and flex at different rates. The thicker bead of silicone offers a safe area for movement without damage to the joint.

For the OPs issue, it would be a good idea to silicone both sides of the acrylic, especially (as others have noted) where the baffle could be subject to pressure from one side and not the other.

 

[Kur]

<a href=showthread.php?s=&postid=15146310#post15146310 target=_blank>Originally posted</a> by BeanAnimal
Glass does not expand when exposed to water, acrylic does (it absorbs water). Some folks reason that a small gap should be left to allow for the swelling and prevent stress on the sump walls. In theory a thick piece of acrylic could put enough stress on a thin (say 10G) sump wall to cause failure.

In any case... Yes in most cases (especially a glass to glass bond) the thinner the silicone layer, the stronger the joint. On the other hand thinner joints are more prone to failure when used on a structure that is prone to flex or movement. The thicker layer of silicone acts as a buffer between the two moving parts. There is a reason that large tank builds incorporate thicker silicone joints. Large panels of glass and their supporting structures expand, contract and flex at different rates. The thicker bead of silicone offers a safe area for movement without damage to the joint.

For the OPs issue, it would be a good idea to silicone both sides of the acrylic, especially (as others have noted) where the baffle could be subject to pressure from one side and not the other.

The OP said he was using glass baffles.

I've never seen an aquarium, no matter how large, with a thick bead of silicone between the panes of glass. A lfs in phoenix has several large 800g+ glass aquariums with the same tight joints as my 150g and 55g tanks.

Also, glass requires a pretty large temperature change to expand or contract enough to tear a silicone joint. My tank is always 80 degrees.

But then again, maybe you've seen something I haven't.

 

[therealfatman]

First glass expansion:
Consider a piece of plate glass 24 inchs long.
Exspansion coefficient a = 5.0 * 1-^-6in/in,⁰ F
Tempearture change = 15⁰F

Diff in length = a*L₀*Diff Temperature F.

Therefore new total length: L₀+L = (5.0 * 1-^-6in/in,⁰ F)*24 inches*15⁰F+24
=24.0018 inches.

IMHO
Ie. no shortening of baffle panels need be done.

Silicone seams/seals: A few pieces of tape to hold the panels in place while applying the silicone. Remove the tap from one seam at a time as needed to apply silicone. For the large compartment walls use a small bead on each side of the glass on the top, sides and bottoms. No spaces need be between any glass surfaces or under the bottom of the glass baffles. For the bubble baffles tape and small silicone beads on one side of the glass panels. Smooth all seams so as to form bubble free neat appearing seams that do not have cavities to hold detritus etc.

Acrylic (extruded sheet):

Exspansion coefficient a =130.0 * 1-^-6in/in,⁰ F
Same conditions

New total length: L₀+L = (130.0 * 1-^-6in/in,⁰ F)*24 inches*15⁰F+24
=24.04 inches
Not an appreciable expansion either.

IMHO
Do not use acrylic baffles in a glass tank

If you choose to use acrylic in a glass tank then remove about 1/16 “ in length to a 24 inch panel or smaller (adjust). Otherthen that trimming install the same way as the glass but with a slightly larger bead of silicone. Do not widely spread the silicone with your finger.

 

[BeanAnimal]

<a href=showthread.php?s=&postid=15147506#post15147506 target=_blank>Originally posted</a> by Kur
The OP said he was using glass baffles.

Yup.. I missed that somehow. The topic comes up quite often here, so the reflex response may have been not to read carefully. And gee... look at the title of the thread! My fault

I've never seen an aquarium, no matter how large, with a thick bead of silicone between the panes of glass.

Reading my post, it appears that my wording was ambiguous. I thought I pointed out that (within reason) the thinner the layer, the more adheshion it offered. I attempted to point out that the thicker beads are used when bonding disimilar materials, so as to allow for thermal expansion and contraction differences between the two materials and that on extremely large bonds, where movement may be expected, a thicker joint may be applicable.

Also, glass requires a pretty large temperature change to expand or contract enough to tear a silicone joint. My tank is always 80 degrees.

The comment was in context to bonds between large disimlar materials, not all glass aquariums where the the panels are made of the same material (it expands and contracts at the same rate).

 

[therealfatman]

<a href=showthread.php?s=&postid=15147998#post15147998 target=_blank>Originally posted</a> by therealfatman

Please excuse me for reposting what seems to be the same information, but I did not notice the mistakes of - instead of (zeros) in the Exspansion coefficient numbers posted.

First glass expansion:
Consider a piece of plate glass 24 inchs long.
Exspansion coefficient a = 5.0 * 10^-6in/in,⁰ F
Temperature change = 15⁰F

Diff in length = a*L₀*Diff Temperature F.

Therefore new total length: L₀+L = (5.0 * 10^-6in/in,⁰ F)*24 inches*15⁰F+24
=24.0018 inches.

IMHO
Ie. no shortening of baffle panels need be done.

Silicone seams/seals: A few pieces of tape to hold the panels in place while applying the silicone. Remove the tap from one seam at a time as needed to apply silicone. For the large compartment walls use a small bead on each side of the glass on the top, sides and bottoms. No spaces need be between any glass surfaces or under the bottom of the glass baffles. For the bubble baffles tape and small silicone beads on one side of the glass panels. Smooth all seams so as to form bubble free neat appearing seams that do not have cavities to hold detritus etc.

Acrylic (extruded sheet):

Exspansion coefficient a =130.0 * 10^-6in/in,⁰ F
Same conditions

New total length: L₀+L = (130.0 * 10^-6in/in,⁰ F)*24 inches*15⁰F+24
=24.04 inches
Not an appreciable expansion either.

IMHO
Do not use acrylic baffles in a glass tank

If you choose to use acrylic in a glass tank then remove about 1/16 “ in length to a 24 inch panel or smaller (adjust). Otherthen that trimming install the same way as the glass but with a slightly larger bead of silicone. Do not widely spread the silicone with your finger.

 

[Reefer2727]

Unfortunately I had siliconed in my first baffle for the bubble trap before I heard the advice to do the middle one first. I gave a quick attempt to the middle one and realized I didn't like they way it was going.

I had some glass baffles cut and they are a little short for my liking. They need too much silicone because the gap is a larger than I would like.

At this point I have cut out the first baffle and have a clean slate again. I am going to get some baffles that are a nicer fit and try again.

I will do the middle baffle first. To do the outer baffles of the bubble trap, do you essentially just silicone the one side of the glass? It seems to tight to actually do a nice job on the inner sides. I fashioned up a hew gadgets for my last attempt but ended up making more of a mess than anything else.

I am hoping it will be much easier with better fitting baffles. The last attempt would have been fine I am sure but I didn't like the mess I made. I know it is a sump and its no big deal but I want it to be perfect.

Any advice? Thanks.

 

[benr]

Also be sure you use the right kind of silicone. You need a acetoxy cure silicone, one made for aquariums. A lot of one part silicones contain Tin catalyst and is toxic to the marine creatures. The Acetoxy can be found at home depot but it is hard to pick the right one. If you want to be safe buy the stuff that is $7/tube and states on it that it is made for aquariums.
Any silicone one part that states that it bonds to acrylic is probablly not the right type.

 

[rguyler]

The good thing is that with glass and silicon if you don't like it, cut it out and do it again.

I am not generally worried too much about appearances in my sump so long as it's a good bond. The neatest sumps are usually the acrylic ones since they can be assembled together with the baffles versus a retrofit of a pre-built aquarium.

To Kur: a "thick" bead is subjective but tank manufacturers avoid squeezing out all the excess silicon making the glue layer extremely thin. Most large tanks have spacers in the silicon to prevent the heavy panes of glass from squeezing out too much silicon. Most tanks, from large to small have enough space between glass panels to at least poke a needle or similar through the silicon so compared to an acrylic build or most other types of glue joints, it's "thick".

 

[rguyler]

Reefer, assuming you're going to go with glass again, get the baffles about .25" shorter than the inside measurement of the tank. This will give you 0.125" (1/8") clearance on each side, which will be good for the silicon joint and not be so tight you can't maneuver it around. The 1/8" gap will also allow you to squeeze a bead between the baffle and tank so you don't have to try to apply it to the baffle edge and then get it into place without smearing the silicon everywhere.

Benr???

 

[therealfatman]

By measurement I found the Aqueon/AGA 120 Gallon tank that is 24 inches tall has a silicone sealant thickeness of 1/16 inch. That is for a seam that is involved in the overall structural integrity of the tank. IMHO Based on that it would seem for all but very large sumps cutting the glass baffle a total of 1/8 inch shorter would possibly work best. Over the years I have found the simplest way to assure that the silicone sealant fills the seam and is not excessively applied is to apply the silicone ahead of the caulking gun tip, not behind the tip. This pushes the silicone into voids rather than just laying a bead on top of the voids where you must try to press the silicone into the seam while smoothing it with your finger.

[b[The Below advice comes from an essortment site:[/b]

Caulking is applied to the joints between parts in a “bead,” which is a continuous stream of caulk laid on the joint by squeezing the trigger of the gun and moving the tip of the caulk tube simultaneously. The key to getting the correct size bead of caulk is cutting the tip of the tube to the proper size and angle. The caulk tube comes with a tapering tip, allowing you to cut it so that the opening diameter ranges from less than an eighth of an inch up to about three eights. A medium-sized opening of about one quarter inch or less seems to work best for most caulk applications. It is also important to cut this tip off of the tube at an angle of about thirty degrees. This allows the caulk to flow better and gives you more control. Cut caulk tubes with a razor blade or box cutter for a clean, smooth cut.

Most beginners make a big mess when trying to apply caulking. It is an inherently messy job to begin with, so it is essential to have plenty of rags or paper towels on hand to clean up and to wipe your hands. To do a good job of caulking, you will need to get your hands messy, as it is necessary to smooth out the caulk bead with a finger tip. Many people fail to do this, and that is why they do not get a good, watertight seal in their caulk joints. The trick is to lay the bead of caulk along the joint with the caulk gun, and then immediately come back with your index finger, pulling it along the length of the caulk bead so that it flattens and smears the caulk, also forcing it deeply into the seam.

essortment.com/home/caulkingtipsdo_seay.htm

Also IMHO Some people seem find it easier to apply a bead behind the tip (dragging a bead), but this usesand wastes more silicone generally and typically makes for a wider spread out of the caulking when smoothing as more pressure needs to be applied by your finger to fill gaps and smooth the joint silicone sealant. I try to avoid excessively wide seams as they are weaker seams.

 

[uncleof6]

Actually, that is not bad information.

Jim