Caulk Discloration Kohler Undermount Enamled Cast Iron Sink

[Slicker]

Hi, we have a under-mounted Kohler enameled cast iron sink in our kitchen that has a slowly expanding discoloration along the caulking (see attached picture). At first I thought it was mildew, but no amount of Tilex or cleaning would remove the discoloration. Online searches have indicated that this is something that can happen to these types of sinks due to the lack of enameling on the portion of the sink that's beneath the countertop.

My question is there anything I can do to fix this? For example re-caulking the joint after removing the existing caulk?

Thanks

 

[Terry]

To me it looks like a gap in the caulking. I would cut some back and put a layer of caulking there. The gap is either showing a shadow or collecting dirt there.

 

[Sponsor]

 

[Slicker]

Thank you. Regarding cutting back, is that something I can use a 5-in-1 or a utility knife to do? Also, Kohler indicates that 100 percent silicone caulk should be used with their cast iron sinks. Without knowing what caulk was used originally, can (or should) I use silicone to make the repair?

Here's a close up of the discoloration if that's helpful:

 

[Onokai]

I would use very carefully a new single edge razor blade and remove as much caulk as you can and clean again and dry and recaulk with the suggested right caulk .That's mold it looks like in and on the caulk.

 

[Reach4]

Thats mold it looks like in and on the caulk.

I thought it looked like mold too, but I would have thought Tilex would have removed that. A bleach solution should have a big effect on mold.

 

[Onokai]

I have seen mold get into the latex caulks and stay there no matter what. That's why I suggest cutting it all out and starting over

 

[Jeff H Young]

yep what everyone said. the problem with many castiron sinks the self rimming style not being enameled at edge and underneath and rust appears. But yours is a tile in / or undermount style with no such problem.

 

[Slicker]

Great, thanks everyone. I tried a technique I saw on YouTube that saturates some toilet paper with bleach cleaner and places it up against the caulk for an extended period. This did improve the stain but did not actually remove it (here's the video if anyone is interested:

). It is a mold of some sort but so embedded in the caulk that normal surface cleaning doesn't affect it. Looks like I'll need to re-caulk if I want to remove it completely.

 

[Reach4]

Great, thanks everyone. I tried a technique I saw on YouTube that saturates some toilet paper with bleach cleaner and places it up against the caulk for an extended period.

I would try chlorine bleach instead of bleach cleaner.