There is supposed to be sealing gunk between the sink and the counter, same as with a top mount sink, though on the inside, rather than outside. Yes, you can and should clean it. Just run your sponge or brush or whatever around the edge there. Stuff shouldn't collect there unless you have a big mess. Then you clean it up, as usual. :) Leaks can eventually happen, but if you regunk you're good to go. The edge can chip if you really bang on it. The type of stone determines how hard or easy it is to chip. It's not a constant occurrence, but stuff happens over time. Some stones are much more prone to chipping than others.

I wouldn't be afraid of an undermount sink unless your crew are really careless.

Thanks plllog -- thanks for the info -- I'm still being teased about the corn plant that sprouted in the dish drainer side of my double bowl sink a while back....I'm most definitely not a neat freak (that thing was pretty tall before someone noticed it....), but I can scrub and bleach my topmount sink whenever the spirit moves me. That sealing gunk might not hold up for me!

There is a third option -flush mount. Not top mount, not bottom mount. Eliminates the gunk collection problem.

There is a thin seam which gets siliconed. Wipe it down every day and you will never have gunk!

I previously had a top mount, but when we remodeled our current kitchen, we went with an undermount stainless steel sink and granite counters.

We aren't the neatest crew and my husband splashes like a toddler in a tub when he does the dishes. And neither of us is careful of the granite (pots, pans, oven roasters banging the edges of the granite) and we haven't had a problem. No leaks around the sink, no cracks or chips on the granite.

Cleaning the undermount is actually easier because I feel like we were always scrubbing where the edge of the top mount met the countertop. This way even if there IS any stuff where the undermount meets the countertop, you don't see it. But when you do one of your "thorough" cleans, you can clean there pretty easily.

Same for where the faucet is mounted...way more effort to keep that area clean on a top mount sink. With the undermount sink, wiping around the faucet / granite area is easy!

Major vote for undermount sink here!

Doesn't how gunky the seal gets depend on what kind of reveal you have? What kind is best--positive, even, or negative? Also, not exactly related to gunk around a sink, but definitely related to undermount sinks, what happens if the sink needs to be replaced? Do counters have to be ripped out?

Okay, I started the "gunk" thing. I wasn't talking about grime gunk, but caulk or plumber's putty or whatever gunk it is that they seal the sink with!!! The good thing to have. I think OP got that, but plant growing in sink? I'm not sure that there's any sink proof to that!!! Undermount shouldn't be any worse than any other kind of sink for that (assuming you also wouldn't be wiping down the rim of Pharaoh's flush mount either. Maybe not good in a super humid environment where fungus grows really easily.

The kind of "gunk" plllog is talking about should be silicone caulk. It's a sealant and adhesive; it helps glue the sink to the stone and seals the joint as well.

How often should we "re-gunk" our undermount sinks? Since we are talking about this...any rough ideas?

And, do you need to "un-gunk" the old "gunk" first?

Just curious.

"How often should we "re-gunk" our undermount sinks?"

A quality caulk (especially silicone) lasts a long time unless excessive scrubbing starts to remove it.

If the joint is tight and the caulking done well (putting caulk on the rim of the sink before tightening it in place and then cleaning up the squeeze out) the seal should last almost indefinitely.
It is not exposed to much of anything except on the sink side to water.

Of course using a knife to try and scrape the joint clean will remove the seal.

My sink gets gunk even with a small household and relatively little use. Am I doing something wrong?

Shelly:

Your sink is leaking; hence the crud. It cannot be fixed topically. The sink must be dropped, the bottom of the stone and the sink flange cleaned throughly, the flange siliconed, and the sink strapped, not clipped or blocked, back in place.

It is the silicone between the stone bottom and the sink flange that does the waterproofing, not a puny little topical bead on the surface of each which inevitably become contaminated and fails.

Thank you for letting me know. How do I convince my builder of that this is the issue so they will fix it?

Joseph, is there a way to test for a leak?

Shelly:

See if you can slide a steak knife between the stone bottom and the sink flange please. If you can, there is no silicone between the stone bottom and flange, hence your leak. Your recurring crud is all the evidence you need that your sink is leaking.

It's not a leak in the drip sense, it's a leak in the capillary action sense. If the gap were sealed, it couldn't leak. If the gap were wider, it couldn's suck dirty sink water between the stone bottom and the sink flange. Unfortunately, your gap is just right.

Here's what your sink flange looks like, I promise: