Thanks, all, for these messages. I think the grout is epoxy, as stoneonecorp guessed, because he mixed multiple small batches and worked very quickly, and I didn't see anything sand/cement-y involved. And I'm glad to hear that non-experts can redo that caulk sink seal with no apparent trauma. I was surprised when he told me that *I* should caulk over his grout seal. This is a guy who was recommended *very* highly by a lot of people: I called every single person on his references list and asked a lot of very critical questions. No one, not a single person, said, "he expected us to finish up the job; he told us to caulk our own counters." ISn't that part of the installation? Anyway, I think I know the answer to that. And given that he whined when we asked him to come back and re-seal the sink (which he messed up the second time as well as the first time -- all the while complaining that no other homeowner had ever asked him to do this, and that the sink is not his responsibility), I don't want him back in my house, because I think he's a jerk. So: sounds like I should recaulk the sink seal and caulk over the grout he laid. Yes? I'm going to use clear silicone and masking tape, so it looks nice. Any other tips, advice, cautions? Pamkcs, did you just rip the old sealant out with a screwdriver and clean what was behind it? As before, thanks in advance!

I realize these comments were from several years ago but I too have this issue and, I am not a slob and I live in Massachusetts where heat and humidity are limited to a couple months a year. However, I will begin to use a toothbrush to clean this area regularly. Although the mold has become visible it is very hard to reach. I never have known anyone to need a toothbrush to clean where the sink and counter-top meet but I am going to begin using a toothbrush regularly to reach this area. I would think twice before getting another under-mount sink. The black mold that builds up is disgusting and almost impossible to reach. I am going to replace the molding today with the mold resistant caulking someone mentioned in this thread and see what happens.

any wood piece that spans across the two cabinet sides is a fine fine support. The sink setter is good too because it looks like a product sold as a product, and there are many people who need that kind of reassurance which is all psychological. Both A and B above are a larger structure than a series of individual clips (not connected to each other in a larger structure). Since they both are attached to the cabinetry, they don't need to grab onto the stone or quartz or whatever material countertop. Any form of grip / grab onto the underneath of the countertop material has its disadvantages; therefore your sink support should have a mechanical con nection to the cabinet. Here is a description of the disadvantages of using some other method as the sole means of mechanical support: 1. Holes drilled in a countertop weaken it. If it cracks one day, you lose. . 2. Silicone is strong but is not proven to be strong enough all the time. Silicone is never sold as a mechanical fastener, by the way. So, what this means is that "a number of clips" is a method that is less than ideal, less than the best, and not to be recommended. The clips have to be attached with some kind of glue or screws going into (new weakness) holes. Any ONE clip might be less-well-aligned compared to the others and it might end up taking a lot of the mechanical stress, and if so this then puts all the mechanical stress onto one new screw hole or one glued clip. In reality, this IS what happens. It is possible to use glue sold as glue (that's not silicone), and which is designed to grip onto stone. But this kind of glue might work or might only work half as well as expected. Ya never know. Just put a cross bar from side to side and you will have done more work in less time. Hth

Not advised to create a ledge. You physically can, but now you depend on silicon to keep things water tight. If you keep a zero reveal or an overhang, then water is less likely to accumulate on the sink flange (Which is used to create the ledge). The silicone then can stay intact longer, and not be needed as the primary water guard. Often the biggest problem we see with ledge sinks is with the installation. Some issues we have been told is with accessories not fitting. However, this is easily avoidable with two best practices: 1. The fabricator should always follow the template 2. Once the hole is cut for the sink, dry fit the accessories to ensure smooth sailing from the client. If you like ledge sinks then check this new release: Kraus Kore