I am working towards re-siliconing a tank and I'm looking to acquire some black reef safe silicone but unable to find a general agreed upon "best" or "safe"
I use GE Silicone I. The key you need to find is 100% silicone, no anti-mold or additives of any kind. I prefer clear silicone, so I have never looked for black. However, BRS definitely sells black silicone if you really can't find it at a hardware store.
Sorry about being a little late to the party. Been away for a few days.
I and others I know have been using ASI for a number of years. If you go to their website, look at the strength of their silicone and compare it to many others, you'll discover it is stronger. Also, it is 100% reef safe so there is not any wondering if it might cause problems down the road. As you will learn, in the following article, some silicones are simply not safe for aquarium use. Even some that many folks claim are safe.
Here is a very good article;
For the record: All silicones are reef safe-once they are fully cured. The enemy is uncured silicone, not some mythical ingredient for controlling mildew.
That said, GE Silicone I is cheap junk. It is the aboslute barrel bottom of all materials (and many silicones are right there with it.) For our projects we really should move up to a higher quality product. Dow Corning makes several that blow GE Silicone away, but are not as hefty as the RTV100 series or SCS1200, however for small projects they are fine. DC 735, DC 999A to name two.
The MSDS for Silicone II does not indicate that there are any additions other than siloxanes, of which there are literally hundreds, (polymers) common to all silicones, without getting to complicated about it, The MSDS also does not indicate any proprietary additives either. Where such is present, the law requires that they be included in the MSDS. This raises serious questions as to the validity of the advertising.
What differentiates Silicone II from Silicone I is the latter is an acetoxy cure silicone, and the former is a neutral cure silicone.
Silicone II does not take longer to cure; published cure times are about the same. However the cure times pertain to a specific amount of silicone, usually given in a bead size, generally 1/8" or 1/4". Hardly have I ever seen an aquarium application use that little. As the amount increases the cure time increases, a week, two weeks...RTV100 series' 7 day full cure time is for a 1/4" bead!
I would say that neutral cure silicone is a bit more toxic in its "uncured" state than acetoxy cure silicone, but that is as far as it goes. It is better to malign a product for what it does not do well, rather than internet rumor.
Acetoxy cure silicone excels at bonding to glass and ceramics; acetic acid is corrosive, so it is not suited for metals, and it does not bond well to other materials (acrylic included.) Neutral cure excels at bonding metals (non-corrosive) and other materials (acrylic not included.)
Co-polymers, are another category (not 100% silicone) and are out of the scope of this thread.
Within the two general categories, there are several sub-categories: sealant, adhesive, high temperature, etc. Obviously we are only concerned with sealants and adhesives. the choice of which to use, really takes little thought. Sealants seal, adhsives hold stuff together.
GE Silicone I (Momentive) is, easy to work with, but is a bargain basement low end sealant. RTV100 series (Momentive) or SCS1200 (Momentive) are high end adhesives, not so easy to work with. In between there is a plethora of formulations, that will drive the most studious nuts ( I am a prime example.)
A short list has been publised at least a 100 times here on RC, not that they are the only choices, but everytime some off the wall silicone is asked about, or mentioned, it just adds to the confusion (and rumors.) In similar fashion "what is safe and unsafe" has been published at least the same number of times, over the past several years, here on RC.
The ingredient is not mythical, mysterious perhaps; The manufactures (claim to) literally add fungicides to the solution. What that fungicide is may be some sort of intellectual property so that may be why the manufacturers don't share the information. SCS1700 does specifically say in their datasheet to not use it in aquariums.
The MSDS for Silicone II does not indicate that there are any additions other than siloxanes, of which there are literally hundreds, (polymers) common to all silicones, without getting to complicated about it, The MSDS also does not indicate any proprietary additives either. Where such is present, the law requires that they be included in the MSDS. This raises serious questions as to the validity of the advertising.
They don't have to. The fungicide is likely in such trace amounts that it does not create a safety hazard (to people). The MSDS for the SCS1700 (which their datasheet claims to have an added fungicide) also doesn't list it. We cannot use the MSDS as an authority for what is in a product. If we could, we all be using ice-melter instead of expensive calcium additives.
That said, thanks to Amazon, SCS1200 is readily available to me now (without having to buy a whole case, lol). So I'll switch up the next time I buy for sure!
It was explained to me many years ago that neutral cure silicones like GEII are inherently more mold resistant than their acetoxy cure counterparts. There are no mold inhibitors added, but it’s not false advertising per se. Either way, I’ve always used the black ASI stuff. FWIW, ‘resealing’ an aquarium is mostly an aesthetic exercise. Makes the human feel better, but does very little structural difference.
I've used them all, like most others have said... the go-tos are Momentive RTV 103 or 108, ASI and GE1 in that order for me. GE1 is the easiest to find (local hardware store) and will work fine in most cases. For larger tanks I go with Momentive RTV or ASI. I know a couple tank manufacturers that use ASI. I've found Momentive RTV is easier to use. If doing a reseal be sure to buy an extra tube or two, running out 3/4's through a project is no fun.
I've used them all, like most others have said... the go-tos are Momentive RTV 103 or 108, ASI and GE1 in that order for me. GE1 is the easiest to find (local hardware store) and will work fine in most cases. For larger tanks I go with Momentive RTV or ASI. I know a couple tank manufacturers that use ASI. I've found Momentive RTV is easier to use. If doing a reseal be sure to buy an extra tube or two, running out 3/4's through a project is no fun.
