Any truth to this - The Planted Tank Forum
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post #1 of 13 (permalink) Old 05-16-2012, 03:59 AM Thread Starter
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Any truth to this

I was at a tannk maker's place today trying to get a custom tank made. All went well until i mentioned using black silicon. He said that black silicon fails quicker than clear as the black is just the clear with other stuff added slit doesn't bond as well. He claims that tank built to the same specs in black and clear, the seams of the black always fail earlier.

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post #2 of 13 (permalink) Old 05-16-2012, 03:54 PM
Are these real?
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Based on the fact that many aquariums are made with black silicone, and that they are not necessarily lower end, I would guess that this isn't true.

Black silicone might be harder to source than clear.

Perhaps if you have two identical tanks, one clear one black, and treat them equally, the black one will fail earlier, but this might happen after 100 years, so difficult to test for and prove.
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post #3 of 13 (permalink) Old 05-16-2012, 04:05 PM
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I would assume he has clear in stock and rather than add more overhead to create your tank, he would prefer to talk you out of black. My tanks have black silicone. I have no Idea at the truth but it sounds like hogwash.
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post #4 of 13 (permalink) Old 05-16-2012, 06:20 PM
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Offer to buy the silicone yourself. As long as you get GE SCS 1200 series he shouldn't complain.
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post #5 of 13 (permalink) Old 05-16-2012, 07:00 PM
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I suspect that the guy is right. Silicone is clear, so the only way to make it black is with a pigment, and that pigment isn't likely to make the silicone stronger, either in bond strength or tensile strength. But, as Wasserpest noted, that might reduce the life of the silicone joints from 100 years to 90 years. In any case I would bet that there is data available on what the comparison in strength is.

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post #6 of 13 (permalink) Old 05-16-2012, 07:31 PM
Are these real?
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Conversely, if he makes the impression that many of his black siliconed tanks failed, I would be hesitant to trust the clear ones...

If he is just concerned from statistics and hearsay, then... ok.
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post #7 of 13 (permalink) Old 05-16-2012, 09:12 PM
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When I was getting my tank made, the builder tried to talk me into black silicone. I'm guessing it's because black silicone hides imperfections much easier than clear.

If I had to guess, I'd say that what hoppy said is right. Whether or not it fails during your lifetime probably won't be due to the color, but to the way it was built.

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post #8 of 13 (permalink) Old 05-18-2012, 12:54 AM
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I'm going to have to go with Hoppy on this one. The majority of Perfecto/Marineland tanks have used black silicone for a while, and we've not heard of massive failures left and right so it cannot be a difference of "tank fails in 90 years vs 10"
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post #9 of 13 (permalink) Old 05-18-2012, 07:06 PM
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I'm not versed in how black silicone is made, but the most common additive for making a plastic black is using carbon black, which is a fancy word for ash or soot. Adding it will increase the strength and stiffness of silicone, and would also improve resistance to UV degradation if silicone didn't already have high resistance. I couldn't find any drawbacks to using the stuff other than a loss of transparency. Perhaps it doesn't flow as easily since it is stiffer?
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post #10 of 13 (permalink) Old 05-19-2012, 02:08 AM
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Normally I agree with Hoppy, and I guess I do here as well, but seriously... if you want black silicone, get black silicone. If the guy can't do it in black than he can't do it in clear either.

SCS1200 Construction
A high-strength, acetoxy silicone sealant providing outstanding adhesion and long-term performance for use in a wide variety of structural glazing and general glazing applications.

Joint Movement Capability (ASTM C719)- +/- 25%
Ultimate Elongation- 513%
Ultimate Tensile Strength- 480 psi (3.31 MPa)
VOC- 23 g/L
Work Life (tooling time)- 5-10 minutes
Food Contact- See data sheet

The info says nothing about differing tensile strengths between black, clear or white.
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post #11 of 13 (permalink) Old 05-19-2012, 02:13 AM
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*Double post but my first reply failed so I did rewrite my post...

Same tensile strength in every colour, so there should be no issue. Normally I don't disagree with Hoppy, but if you are willing to trust silicone to hold together an aquarium (a completely ridiculous application for silicone) than trust the black as well. If your builder won't do it find another.

It's like not using crest because of the blue stripe, yet you'll use colgate.

Last edited by jcgd; 05-19-2012 at 02:45 PM.
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post #12 of 13 (permalink) Old 05-19-2012, 03:44 PM
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who woulda thought that silicone could withstand hundreds sometimes thousands of pounds of weight with nothing but a few small seams..

that blows my mind
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post #13 of 13 (permalink) Old 05-22-2012, 12:06 AM
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Actually, I can see the black silicone lasting longer than clear, for no other reason than it is opaque, IE stops UV light damage past the surface. At any rate, the amount of lampblack (carbon) they would add to a tube of silicone to make it black would be less than a gram. I could see an additive making the silicone stronger in some situations if you used chopped carbon fiber. Although that might end up greyish black
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