Undermount Kitchen Sink Silicone Mouldy

[emmaamme]

Hi, the silicone on my undermount kitchen sink is 3 years old and is black from mould. No leaks but wondering if it should be replaced. I've tried cleaning it with bleach & with vinegar but nothing seems to shift it.
It's a stainless steel sink & wondering if the whole sink would need to come out, silicone taken off & then resiliconed before refitting (on which case I'd get a plumber in) or whether I can scrape it out & then reseal without taking it out.
It doesn't seem to have any clips on the sink holding it in place so I'm guessing it's adhesive that's holding it in.
Looks an awkward gap for getting a silicone nozzle into so any tips would be gratefully received.
I've attached some photos to show the problem.

Thanks.

 

[Madrab]

Have you ever considered that it isn't silicone, nor was it any other colour to start with? Unless you fitted it of course

It looks like a black silicone/epoxy adhesive that's been used.

 

[emmaamme]

It was formerly white as certain parts are still white in colour so guessing it is silicone

 

[MJN]

When you say 'an awkward gap for getting a silicone nozzle in' do you have the long cartridge guns in mind? If so, you can also get silicone in toothpaste-type tubes which ought to be fine for manoeuvring around the inside of the sink.

If it's not clear how the sink comes out I think I'd be looking to scrape out what I could of the old silicone and reapply, perhaps filling it more to reduce the quantity of water that can hang around at the interface.

 

[Burnerman]

Hi Emma, slightly off the silicone topic but can you check that the sink bowl is actually supported underneath?
The reason I’m asking is because I have seen a number of these where the bowl is just siliconed in place, and after a while they just fall through
Seriously!
John

 

[emmaamme]

Thanks - yes I was thinking of the cartridge gun which would be awkward so that's a good shout.

 

[emmaamme]

Hi John, there's no support underneath at all but there is adhesive bulging out from the underneath of the sink edge where it's glued to the worktop.

 

[Madrab]

The reason why I say that is looking at the pictures (pic 4) it doesn't have the typical look of white/clear silicone that's gone black, it really looks like a black adhesive. That being said pictures can be deceiving sometimes.

 

[emmaamme]

I know what you mean - it's just gone very mouldy as it's an awkward area for catching water/food etc

 

[Burnerman]

I’ve seen three occasions where the bowls have parted company with the granite.....very expensive kitchens they were too. It was largely the drains that were holding them up
I braced them with timber bearers after the repair was made.
John

 

[emmaamme]

That's unreal. Touch wood not had a problem over last 3 years. Did you have to use clips to fix them?

 

[Burnerman]

Basically these sinks had fallen an inch or so, but not evenly so it was off with the old silicone and on with the new. I then jacked the sink upwards tightly into place and reinforced things by adding some 50 x 25 mm timber underneath the bowl to take the weight.
I don't know what the usual practice is for securing sinks but for sure it wasn't good enough on these occasions....maybe CT1 or similar would have been better.
John

 

[Sonic70]

Because it was not filled to the edge with silicone its just trapping water in the gap between sink and worktop, hence mould grows.

 

[emmaamme]

I wonder if it was maybe done that way to keep it out of view? So I'm guessing if I redo it I should fill it more to the edge.

 

[Burnerman]

Definitely fill all of the gaps with silicone - any water which can run underneath will come back to haunt.
There is a substance called silicone remover which tends to dissolve the stuff and it works to a degree, but usually leaves a gooey mess. It could be worth a try I guess.
John