Silicone for sump baffles
- Thread starter irishfan
- Start date
uncleof6
Active member
Probably not, as there are more oddball silicones out there than anyone can keep track of. The above pictured product is a consumer grade sealant. There are far higher quality silicones made by Dow Corning (the folks that make DAP silicones) that are better suited for the purpose, such as DC 999A, DC735, and both are far superior to silicone I and II, which really aren't suitable for the purpose either, despite their widespread recommendation.
muttley000
MTS Sufferer!
Uncle,
Any problems using these in an aquarium, they don't list that specific use.
Thanks
Any problems using these in an aquarium, they don't list that specific use.
Thanks
Unless you are planning significant level differences between sump compartments, there simply isn't much pressure on the baffles, so crappy stuff like GE I works fine I think. I'm paranoid, so I bought a few tubes of the Aqueon sealant for my baffles, but likely unnecessary. Just make sure to let it cure for at least a week.
igadget56
Member
Something to consider. True??? :uhoh3:
http://www.frogforum.net/vivarium-t...o-longer-safe-due-added-mildew-inhibitor.html
http://www.frogforum.net/vivarium-t...o-longer-safe-due-added-mildew-inhibitor.html
nemosworld
Active member
http://www.amazon.com/Corning-999A-Silicone-Glazing-Sealant/dp/B000WTZKMW
http://www.amazon.com/All-Glass-Aquarium-AAG65010-10-3-Ounce/dp/B0002ASD34
http://www.amazon.com/Marineland-31...upplies_5?ie=UTF8&refRID=0K322W4800NNT7XZV3PA
http://www.grainger.com/product/MOMENTIVE-Silicone-4UH12
http://www.amazon.com/Black-Aquarium-Silicone-Sealant/dp/B00EZB2MDI
http://www.amazon.com/All-Glass-Aquarium-AAG65010-10-3-Ounce/dp/B0002ASD34
http://www.amazon.com/Marineland-31...upplies_5?ie=UTF8&refRID=0K322W4800NNT7XZV3PA
http://www.grainger.com/product/MOMENTIVE-Silicone-4UH12
http://www.amazon.com/Black-Aquarium-Silicone-Sealant/dp/B00EZB2MDI
uncleof6
Active member
There are a great many myths floating around concerning silicone. Some are due to not understanding the advertising, to flat out "misleading" advertising; from repackaged silicones claiming "aquarium" safe, to OMG mildew inhibitors will slaughter your fish.
The beginning: Back in the day, 30 someting years ago, GE0A12 silicone was labeled "Aquarium Silicone." No one, professionally anyway, used it to build aquariums. Folks figured they could build aquariums with it, and did. The resulting catastrophic tank failures resulted in a rather heavy lawsuit. The result of the lawsuit was the removal of "Aquarium Silicone" from the label. GE0A12 is still on the market, a product you all know as Silicone I, Window and Door. It is FDA approved for food contact, and as such is "safe" for use in aquariums. It is however, a bargain basement sealant, that has no strength whatsoever. It is intended for sealing, not bonding things together, whether it be tank walls or sump baffles. That said, folks use it for baffles, and generally the baffles don't blow out, and when they do, it is usually due to using acrylic baffles, or glass that is too thin. Having said that, it cannot be said it is the best suited for the purpose, due to its shortcomings in the strength department. (There is a pressure difference between sections in a sump. 1" water level is enough to cause the baffle to deflect to the side with less pressure. There is nothing equal—or close enough, between sections in a sump.) There are better silicones available, without resorting to the heavy hitter industrial adhesives.
Aquarium safe: There are no silicones that are labeled (from the manufacturer) as aquarium safe. The labels say "not for use underwater." So labeling "aquarium safe" is rather contradictory false advertising on the part of the repackager. Having said that, about the only one that has their neck out on a limb, so to speak, is Aqueon/AGA with their branded, repackaged Dow Corning product, aquarium silicone, "the silicone used to build their tanks" loose quote. Well, looking at the msds, and product data sheets shows it is a consumer grade sealant, little better than GE I, and a tour of the facilities revealed crate after crate of Momentive RTV100 series...no, the msds/product data does not match that of the branded silicone.
What is safe: Everything and nothing. Everything if suitable for the intended purpose, and you let it cure 7+ days. Nothing if it is unsuitable for the purpose, and you don't let it cure long enough.
The general recommendations are:
1-part Acetoxy cure*
100% Silicone (does not contain co-polymers such as acrylic)
FDA approved for food contact. (albiet rather vague)
*Neutral cure silicone does not bond to glass as strongly as acetoxy cure silicone. Acetoxy cure silicone does not bond to other materials as well as neutral cure. However, acetoxy cure silicone is corrosive, so if bonding glass to metal, neutral cure is the better choice.
Mildew inhibitors: Again, misleading advertising, and the linked information above is most certainly false (post #8.) Looking again at the msds for Silicone II, there are no constiuents listed, or proprietary ingredients listed that are inconsistant with that contained in every neutral cure silicone on the market. E.G. nothing that is an additive for mold/mildew inhibition. The law requires that such be listed by "name" OR listed as a proprietary ingredient, by percentage. If we are to believe that Silicone II will kill off a tank, we must believe the same of Dow Corning 795 (also a neutral cure), yet it is used by many public aquariums. The problem with ALL silicones is the cure time is longer with our application, than what is listed on the label. Uncured silicone will kill off a tank, acetoxy or neutral cure. So, in a sense, every silicone on the market will kill off your tank—if you don't let it cure...there is a tendancy for "hobbyists" to blame anything on everything other than 'the hobbyist' for their failures...such was the case with the lawsuit against GE: They should not have been building tanks with it...
The beginning: Back in the day, 30 someting years ago, GE0A12 silicone was labeled "Aquarium Silicone." No one, professionally anyway, used it to build aquariums. Folks figured they could build aquariums with it, and did. The resulting catastrophic tank failures resulted in a rather heavy lawsuit. The result of the lawsuit was the removal of "Aquarium Silicone" from the label. GE0A12 is still on the market, a product you all know as Silicone I, Window and Door. It is FDA approved for food contact, and as such is "safe" for use in aquariums. It is however, a bargain basement sealant, that has no strength whatsoever. It is intended for sealing, not bonding things together, whether it be tank walls or sump baffles. That said, folks use it for baffles, and generally the baffles don't blow out, and when they do, it is usually due to using acrylic baffles, or glass that is too thin. Having said that, it cannot be said it is the best suited for the purpose, due to its shortcomings in the strength department. (There is a pressure difference between sections in a sump. 1" water level is enough to cause the baffle to deflect to the side with less pressure. There is nothing equal—or close enough, between sections in a sump.) There are better silicones available, without resorting to the heavy hitter industrial adhesives.
Aquarium safe: There are no silicones that are labeled (from the manufacturer) as aquarium safe. The labels say "not for use underwater." So labeling "aquarium safe" is rather contradictory false advertising on the part of the repackager. Having said that, about the only one that has their neck out on a limb, so to speak, is Aqueon/AGA with their branded, repackaged Dow Corning product, aquarium silicone, "the silicone used to build their tanks" loose quote. Well, looking at the msds, and product data sheets shows it is a consumer grade sealant, little better than GE I, and a tour of the facilities revealed crate after crate of Momentive RTV100 series...no, the msds/product data does not match that of the branded silicone.
What is safe: Everything and nothing. Everything if suitable for the intended purpose, and you let it cure 7+ days. Nothing if it is unsuitable for the purpose, and you don't let it cure long enough.
The general recommendations are:
1-part Acetoxy cure*
100% Silicone (does not contain co-polymers such as acrylic)
FDA approved for food contact. (albiet rather vague)
*Neutral cure silicone does not bond to glass as strongly as acetoxy cure silicone. Acetoxy cure silicone does not bond to other materials as well as neutral cure. However, acetoxy cure silicone is corrosive, so if bonding glass to metal, neutral cure is the better choice.
Mildew inhibitors: Again, misleading advertising, and the linked information above is most certainly false (post #8.) Looking again at the msds for Silicone II, there are no constiuents listed, or proprietary ingredients listed that are inconsistant with that contained in every neutral cure silicone on the market. E.G. nothing that is an additive for mold/mildew inhibition. The law requires that such be listed by "name" OR listed as a proprietary ingredient, by percentage. If we are to believe that Silicone II will kill off a tank, we must believe the same of Dow Corning 795 (also a neutral cure), yet it is used by many public aquariums. The problem with ALL silicones is the cure time is longer with our application, than what is listed on the label. Uncured silicone will kill off a tank, acetoxy or neutral cure. So, in a sense, every silicone on the market will kill off your tank—if you don't let it cure...there is a tendancy for "hobbyists" to blame anything on everything other than 'the hobbyist' for their failures...such was the case with the lawsuit against GE: They should not have been building tanks with it...
Question - by cure do you mean dry or with water? We probably overthought this with our sump build, but we let the silicone sit for about a week dry and then another week filled with tap water to remove anything that was going to leach out right away. From what I read, it seemed like we should do both, but I was never sure which one was considered curing. Figured now was a good time to ask!
uncleof6
Active member
<sup id="cite_ref-roux_1-1" class="reference">Silicone is a Room Temperature Vulcanizing "rubber like" product. It is an inorganic synthetic elastomer. It is composed of Carbon, Hydrogen, Oxygen, and Silicon, (think silicon dioxide, SiO<sub>2</sub> a major constituent of glass,) reinforced with a filler, usually fumed silica.
Just like rubber, silicone does not "cure" in the sense that we "cure" rock. With rock, 'cure' is a misnomer anyway. We are not relieving any illness or disease in the rock, we are not preserving the rock by adding salt, drying, smoking etc, and it is certainly not vulcanizing like rubber and silicone do. We allow the decay of dead orangic matter to complete, before adding it to the tank, but with a new tank startup, that is a bit silly, but not the topic of this thread.
Silicone does not dry, if it did, it would crack and fall apart. It vulcanizes at room temperature. Vulcanizing by definition, is the process of altering the physical properties by treating it with sulpher, or sulpher compounds, under heat and pressure to improve elasticity and strength, or produce a hard substance. (one such product was called gutta percha in the 1800s, which was the grandfather of modern plastics.)
Silicone is RTV (room temperature vulcanizing"”All silicone is RTV, so packaging stating RTV is not a qualification for "our purposes;" the RTV we speak of is a specific branding by GE/Momentive.
The 'curing' process, called a condensation process, (or tin based cure system) is a bit complicated, but it is the process used for the silicones most often used in the hobby, (not neutral cure,) but reveals some interesting points:
"An alcoxy crosslinker exposed to ambient humidity (i.e., moisture) experiences a hydrolysis step and is left with a hydroxyl group. This group then participates in a condensation reaction with another hydroxyl group attached to the actual polymer. A tin catalyst is not necessary for the reaction to occur, though it increases the rate of the reaction and therefore decreases the cure time. No mixing is required for the reaction to take place. Such a system will cure on its own at room temperature and (unlike a platinum-based system) is not easily inhibited by contact with other chemicals, though the process may be affected by contact with some plastics or metals and may not take place at all if placed in contact with already-cured silicone compounds. It may take as long as a week for the system to cure fully, and as the system requires some water from the atmosphere in order to cure, there is a risk of the surface layers curing enough to seal the lower layers away from the air, resulting in a fluid pocket of uncured and uncurable silicone (this not a risk for addition-based systems). Acetoxy tin condensation is one of the oldest cure chemistries used for curing silicone rubber, and is the one used in household bathroom caulk. The smell of vinegar in the form of acetic acid is the usual indicator that the reaction is incomplete. Non-acid-producing formulations (neutral cure) also exist which have a shorter shelf-life, however, and reduced adhesion when finally cured."
To answer one of your comments, about submerging the curing silicone in water, raising the humidity is a plus, like a 1/8" of water in the bottom of the tank, can speed up the curing process, but it is still best to wait a week or more, because of the copious amounts (over 1/4" beads) used for our application. So, basically it was a waste of time, as there is nothing to "cure" once the silicone is fully vulcanized/crosslinked. Once cured, (fully vulcanized/crosslinked) silicone does not leach anything into the water, and is chemically inert.
Just for grins, silicone is a misnomer as well. The suffix _one is used by chemists to denote a substance with a double-bonded atom of oxygen in its backbone. The thought was erroneous because the polymer does not have oxygen atoms bonded in this matter. The correct term would be polysiloxanes, or polydimethylsiloxanes. These are the type of terms you will find in the MSDS, so it is fairly easy to pick out stuff that "does not fit" in the search for the infamous "mildew inhibitor." In colored silicone, there is a dye that is used in food coloring, so have to watch out for that as well.
</sup><sup id="cite_ref-roux_1-1" class="reference">
</sup>
Just like rubber, silicone does not "cure" in the sense that we "cure" rock. With rock, 'cure' is a misnomer anyway. We are not relieving any illness or disease in the rock, we are not preserving the rock by adding salt, drying, smoking etc, and it is certainly not vulcanizing like rubber and silicone do. We allow the decay of dead orangic matter to complete, before adding it to the tank, but with a new tank startup, that is a bit silly, but not the topic of this thread.
Silicone does not dry, if it did, it would crack and fall apart. It vulcanizes at room temperature. Vulcanizing by definition, is the process of altering the physical properties by treating it with sulpher, or sulpher compounds, under heat and pressure to improve elasticity and strength, or produce a hard substance. (one such product was called gutta percha in the 1800s, which was the grandfather of modern plastics.)
Silicone is RTV (room temperature vulcanizing"”All silicone is RTV, so packaging stating RTV is not a qualification for "our purposes;" the RTV we speak of is a specific branding by GE/Momentive.
The 'curing' process, called a condensation process, (or tin based cure system) is a bit complicated, but it is the process used for the silicones most often used in the hobby, (not neutral cure,) but reveals some interesting points:
"An alcoxy crosslinker exposed to ambient humidity (i.e., moisture) experiences a hydrolysis step and is left with a hydroxyl group. This group then participates in a condensation reaction with another hydroxyl group attached to the actual polymer. A tin catalyst is not necessary for the reaction to occur, though it increases the rate of the reaction and therefore decreases the cure time. No mixing is required for the reaction to take place. Such a system will cure on its own at room temperature and (unlike a platinum-based system) is not easily inhibited by contact with other chemicals, though the process may be affected by contact with some plastics or metals and may not take place at all if placed in contact with already-cured silicone compounds. It may take as long as a week for the system to cure fully, and as the system requires some water from the atmosphere in order to cure, there is a risk of the surface layers curing enough to seal the lower layers away from the air, resulting in a fluid pocket of uncured and uncurable silicone (this not a risk for addition-based systems). Acetoxy tin condensation is one of the oldest cure chemistries used for curing silicone rubber, and is the one used in household bathroom caulk. The smell of vinegar in the form of acetic acid is the usual indicator that the reaction is incomplete. Non-acid-producing formulations (neutral cure) also exist which have a shorter shelf-life, however, and reduced adhesion when finally cured."
To answer one of your comments, about submerging the curing silicone in water, raising the humidity is a plus, like a 1/8" of water in the bottom of the tank, can speed up the curing process, but it is still best to wait a week or more, because of the copious amounts (over 1/4" beads) used for our application. So, basically it was a waste of time, as there is nothing to "cure" once the silicone is fully vulcanized/crosslinked. Once cured, (fully vulcanized/crosslinked) silicone does not leach anything into the water, and is chemically inert.
Just for grins, silicone is a misnomer as well. The suffix _one is used by chemists to denote a substance with a double-bonded atom of oxygen in its backbone. The thought was erroneous because the polymer does not have oxygen atoms bonded in this matter. The correct term would be polysiloxanes, or polydimethylsiloxanes. These are the type of terms you will find in the MSDS, so it is fairly easy to pick out stuff that "does not fit" in the search for the infamous "mildew inhibitor." In colored silicone, there is a dye that is used in food coloring, so have to watch out for that as well.
</sup><sup id="cite_ref-roux_1-1" class="reference">
</sup>
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