Two different granite installers told me they only use 100% silicone. Silicone mixed with latex will get mildew. (I was complaining about my bathroom remodel when they explained this to me.)One of them said "You can't get it around here. we have to send away for it." I can't vouch for the accuracy of this, only reporting what I was told.

Horse pucky. Pure silicone should be on the same shelves that have all the other caulk.
Here's one:
GE Silicone II

Well that's good to know, but is it true that pure silicone won't mildew but the mixed one will?

It IS true that there are some "special" kinds of silicone that are sold to pro's only, but don't let that stop you from going to Lowe's or HD. (This is one of the blessings of having these mega companies around !! Without them, we would be unable to DIY unless we had loads of books, training and/or pro guides).

Around tubs, one places a "siliconized" latex which is designed to be temporary. Yes, it does allow / mold / mildew / whatever / to grow around its edges.

in the bathroom forum you all will find that bathroom renovators know a lot about the various types of silicone and the other products that are "latex"

Hth

well, I can tell you from personal experience that GE Silicone II, when placed at the grout line between the backsplash and granite, behind the kitchen sink (overmount), WILL definitely mold and mildew. I initially had that issue, then caulked it, which lasted about 2 years. Then I switched to the GE stuff, and put it on THICK, and it lasted about 2 years, and I recently scraped it off (it's ALOT harder to scrape off than caulk), and reapplied, except this time, I put a thin layer ON the granite between the backsplash all the way to the back rim of the sink. it's been about 4 months, and looks ok, but I"m not holding my breath.

I tried google searching it, looking for something that would truly work, and found that 'expert' plumbers, etc, all felt that silicone was not that good at preventing mold/mildew, and that regular latex caulk, I forget the actual brand, was the best. In the meantime, my new kitchen will have one piece of granite extending behind the undermount sink into the garden window, with no seam for at least 1 1/2' deep!

actually Kevin, your opinion is worth waaaaaay more than 2c
For the record i have NEVER thought that you were in the least self-promoting,
Always that you are being extremely helpful
thanks always for your words of wisdom

Yes, thats exactly what the pros said.... Poly seam seal! I just forgot the name. Someone brought up that there were different formulations, and they all said that the basic tub and tile one was what they used, iirc. Thanks for jogging my memory, Kevin!

Polly Seamseal. That's a nice name. If I name a pet after it maybe I can remember the name next time.

I have black-looking mildew on the caulking around my kitchen sink. Does anyone know how I can get rid or it or protect the caulking from mildew?

blgros:

You may have a more serious problem than caulk.

Lay on your back inside your cabinet and make sure your sink is secured with mechanical fasteners. Wood shims/granite blocking polyestered in place bridging the sink flange does not count.

If there are no mechanical fasteners, disconnect your drain lines and drive a scraper between your sink and granite until the sink is free. Clean the sink flange and the bottom of the granite and install a Hercules Universal Sink Harness ($5.99 at Braxton Bragg)

Apply a nice fat bead of quality silicone to the flange and tighten the harness while keeping your sink reveal even. Spray the silicone squeeze-out with Windex and wipe off the excess. Use Acetone if you have to.

I have performed this repair at least 20 times. Never a callback, no mold or mildew.

If your silicone joint fails, the flange will dump water onto your reinforcement rodding if you have any. If this rodding is mild steel and set in polyester, it will rust, expand, and crack your granite parallel with your sink and front edge. A guy like me will charge you $800-$1,200.00 to repair it; no guarantees on performance or appearance. I have performed this 3 times and saw my worst one ever yesterday.

When we had some work done on our house I asked about the mold that continue to grow under the sealant between the backsplash and the countertop around the kitchen sink. The guy explained to me that moisture still hanging around in the crack would cause the mold to grow after you applied the sealant. He said the most effective way to keep the mold from growing was to buy denatured alcohol and spray the seam then allow it to dry before applying the sealant then spray it again after you apply the sealant. I have not tried it yet but I do know that denatured alcohol will evaporate anymore just year without damaging the surface or the material. A friend of mine saved my cell phone after I accidentally dropped it in water. I was amazed when he took my phone and removed the battery then dropped my phone into a glass he had filled with denatured alcohol. The denatured alcohol evaporated along with the water that was left in my phone. My phone worked perfectly afterwards. So even though I have not tried this approach with sealant around my kitchen sink, ( only because I can't remember to buy the denatured alcohol) it makes total sense to me that it would be very effective. Mold grows because of moisture, moisture is completely evaporated by denatured alcohol. It's definitely worth a try.

Joseph, I am back again. I had a second counter top put it and was cleaning the sink and noticed there is no caulking inside the sink between the granite and the sink. I looked at the upstairs sink, different fabricator and it does have caulking that is white and looks like the same caulking used around my tub. I called the new fabricator and they said they use a clear sealant prior to setting the sink in place, but if I want it caulked or sealed they can come out and do that, but see it as a possible mold/dirt problem. I said "I do not know what is the right thin to do, I am now the expert", I just want it taken care of properly. I do not want water seeping in the open area and mold growing deep inside. Later I drove over to two model homes. One has the caulking like one bathroom and the other does not like my second bathroom. Which is the right way or are they both okay. HELP!

Look up at the sink flange. Is there any caulk squeeze-out? There should be. See if you can get a very thin knife between the sink flange and the bottom of the stone. You should not be able to.

The silicone caulk that does the work is squished between the flange and the stone. If it is not there, it cannot be applied without dropping the sink. A topical bead between the sink and stone is useless and unacceptable.

What is a sink flange? I am referring to the inside of the sink, where the granite meets the sink. I can see some silicone caulk that looks clear squeeze out in some areas and then open areas, where the knife go in a little deeper and blocked may be more silicone, the knife does not go all the way through. Do you think I'm just being overly concerned?

They are going to come out and seal it more all the way around. They are telling me this is the way they do all their sinks and never have had a problem, (they do a lot of business) but they would be happy to add more. This is a large company here in Utah and have been great to work with, I hope I haven't become a overly concerned. I noticed one model home I visited was similar to mine and the other model home with the same builder had the white caulking all the way around thick and visible. Possibly two different type of caulking.

Underneath the sink I cannot see it has large clumps of the clear glue they use to hold it in place and it is too difficult to get a knife between the cabinet and the sink.

With all of that information- do you think I should have them add the additional silicone caulking, so that I can see it and know there is no water seeping to the pockets the knife sinks in on?

Rosalie Carter:

The vertical sides of your sink bend at the top to horizontal for about an inch where it meets the bottom of the stone. This 1" steel perimeter of the sink is the flange.

A topical application of silicone between the vertical sink side and the stone cut-out does virtually nothing as far as waterproofing. The flange must be loaded with silicone and squished against the bottom of the stone to work properly.

Check you sinks for leaks; it's your only alternative now. Keep an eye on it too.

I have the same problem..can't find a plumber who will come and redo the sealant. Does anyone know if another type of professional who would know how to do?

You need a plumber that will utilize a Hercules Universal Sink Harness (BB Industries) or a Sink Strap or two from Regent Stone Products.