I need to know if this is a steel sink or a ceramic sink. It sounds like a ceramic sink and my answer will be based on that. If it is a stainless steel sink you need to get back to me on that.
I am going to go way out on a limb and tell you that it is not epoxy. If it was epoxy then the sink or the stone would have been broken, not the glue. The reason I said this is your line about "Recently one of the epoxy bonds completely separated from the granite", and in my experience I have never seen this happen unless the glue was superheated to over 300 degrees Fahrenheit. Then again, I am not a know-it-all, but if what you are saying is true it is a first for me!
If it is not epoxy it is either a polyester resin, a mastic or a silicone. All can be clear and all will dry hard but none of them is what I would consider to be a permanent bonding agent like epoxy. Here is a test - If you can cut the epoxy with a razor blade or a scraper then it is not epoxy. You can break razor blades on cured epoxy, and the bond stays that strong unless acted upon by high heat.
My advise would be to strip the adhesive from both the stone and the sink. Scrape it off, maybe use diamond sandpaper (this link)
http://www.defusco.com/diamond-sandpaper-discs-diamond-sandpaper-discs-c-25_30_660_664.htmlOnce you have both pieces free and clean, use 100% silicone to adhere the sink to the stone. A 3/4" bead across the flat part of the ceramic sink top should suffice. Hold it in place with allthread. 5 minutes after you tighten the allthread tighten it a little more as the silicone spreads and thins and you do not want a gap in the silicone. Silicone takes up to 72 hours for a full cure at room temperature with moderate relative humidity. After that you can use anchors or a brace support to help hold it in place. I tell you this because according to the Marble Institute of America the sink should be supported from the ground up as gravity works. If you don't want to brace it from the floor you can always use poly blocks that overlap the lip of the sink and you can epoxy those right to the underside of the slab. If you ever want to change the sink you hit the blocks with a hammer and break them. Part of them will still be glued to the epoxy but you can grind it off if you desire.
Now that I have told you about bracing it, here is my opinion. If it is a bathroom sink it isn't even necessary. First of all it won't get a lot of use and secondly, and more importantly, once the silicone has cured a 250 pound man could jump up and down in that sink and he would bust the sink before the silicone bond let go.
If you have any other questions please feel free to call me days at 800-289-6834.
Glad to be of service,
Mark
Poll
