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We recently had a new metal kitchen sink and Formica counter-tops professionally installed, but the installer did not apply any caulking around the sink. During a follow-up call with the counter-top company, we were told that their installers do not caulk.

I bought some clear General Electric silicone caulk, caulked it myself, and let it dry for several days under a plastic sheet to ensure that it was well cured.

A few weeks after, the caulk started to peel away from the edge of the sink. I had followed the directions on the silicone caulk product, and cleaned the area before applying it.

What's the best way to prepare and caulk a sink so that the caulk doesn't continuously just come away from the edges it's intended to seal?

I want to do it as well as possible, so the caulking lasts months instead of weeks. To be honest, I am annoyed that I have to deal with this myself. We hired professional counter-top installer from a reputable local company to handle exactly this kind of thing on our behalf.

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In that case it's a drop in sink. You caulk them underneath the rim of the sink before placing it in the counter. You won't see the caulk. Are you sure the installers didn't caulk under the sink? Caulking around the rim where it meets the counter isn't a good idea. It eventually looks bad. –  OrganicLawnDIY Dec 18 '13 at 22:33
    
Oh! I never thought to check underneath the sink for caulking. There was no caulk visible, as you said. I've never had a new sink before, so I expected to see a caulk seal like in my old apartments. I will inspect under the sink and blow air at the edge of the sink and feel for breezes underneath with my hand. When we called to ask about the lack of caulk, maybe the company said that they don't caulk the outside of the sink -- and we took that to mean that there was no caulking at all, when in fact we were being told that the caulking was hidden underneath. I will check tonight. –  Steve HHH Dec 18 '13 at 22:46
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I don't understand... if the professional did not install it correctly, why aren't you getting the professional to fix their mistake? –  maple_shaft Dec 19 '13 at 12:17
    
Because when we called the professional to ask whether there was supposed to be caulking around the sink, we were told that the counter-top and sink installers do not caulk. –  Steve HHH Dec 25 '13 at 21:02
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3 Answers

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If the plastic sheet you put over the curing caulk formed a vapor seal, the caulk did not cure properly which could make it not adhere and peel.

Curing caulk should be left open to the air to off gas at its natural rate determined primarily by temperature. As long as the sink is at room temperature this should happen in less than 24 hours. Do not disturb or splash it within the first 30 minutes.

As long as the counter top is an ordinary material—stone, wood laminate, or composite—it just has to be clean and dry before caulking.

I certainly would expect a professional sink installer to caulk. Perhaps they refused because one of the counter or sink materials is known not to work? Oily woods like Rosewood, Ebony, Cumaru, Ipe, etc. are well known to be difficult to glue together. A solvent can be used just before caulking to improve performance. See this.

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Thank-you wallyk. Yes, perhaps the plastic sheet I used prevented it from curing properly. Clearly, I don't know what I am doing, and would have preferred it to have been done by the professional who installed the sink, even if it meant an extra charge. I will remove and re-apply the caulk by removing the sink, letting everything dry, and look for a mild solvent to help with adhesion. –  Steve HHH Dec 18 '13 at 22:30
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Many drop in sinks require the caulk to be applied under the sink before it's dropped in, where it will not be visible. The bead of caulk will be just under the edge of the rim, and any excess is wiped away after the sink is clamped down. Check the installation instructions for your sink to see if this was the requirement for yours, and if so, you may need to pull it out to properly caulk it in place.

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Caulk tends to do that when it doesn't adhere to the surface. Most commonly it doesn't adhere because the surface still has moisture in it, for instance, a porous surface that hasn't dried out yet.

I would recommend removing all existing caulk then letting the area dry out as much as possible for 2-3 days - protect it from water if you use it, but make sure moisture can escape. It's possible that the plastic sheet you're covering it with while it is curing is preventing the moisture from leaving which is contributing to the problem.

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