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How to remove black mould in bathroom on tile?

Hello DIYers,

I am going to be replacing the silicone caulk around the bathtub because it's got black mould on it but before I do so I've noticed that the tile itself seems to have some on it. I'm concerned that if I just replace the silicone that this won't be a long term solution.

I've tried removing what's there using tile cleaner, grout cleaner, vinegar and a plethora of other options but it seems to not budge from the tile itself.

Do I really need to worry too much about it?

Screenshot 2023-04-18 at 3.04.20 pm.png

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EricL

Hello @dchur

Since you've used vinegar, it would have been enough to kill the roots of the mould and mildew. Unfortunately, if the tile has been stained by the mould, I'm afraid the only way to remove the stain is to replace the tile itself. Using stronger caustic chemicals will only damage the surface glaze of the tile.

If you have any other questions we can help with, please let us know.

Eric

dchur

Thanks @EricL , I thought that might be the case.

We do have some extra tiles laying around so we may look at how to replace the 4 affected tiles as well.

dchur

Hey team,

Looks like most of that black mould was on the silicone that had been under the tile and the tiles themselves are in relatively good condition which is good.

Replaced the silicone yesterday with Selleys white silicone and have two queries/worries:

1) It looks like some of the silicone pretty much instantly appeared more yellow/cream than the rest. In this pic you can see the right tile section is perfectly white but the left is cream.

2) Have I applied this too thing on the right? You can see the bottom of the tile behind it and I'm thinking I may have made this too thin now.

It was a big job to remove the existing caulk so I'm not too keen on having to do this again but if I have to rip it out i'd rather that than water leaks..

MitchellMc

Hi @dchur,

There are a number of reasons why the silicone may have discoloured, such as leftover moisture or cleaning product residue stuck in the gaps between tiles. To confirm this, you could try applying silicone in another location to see if it turns cream-coloured or remains white. However, the only way to fix the discolouration is to redo the silicone in that specific area.

It's difficult to tell from the photo whether the silicone is too thin or not. You could try applying a second layer of silicone to build up the thickness and ensure proper coverage. Just make sure that the first layer is fully cured before adding the second layer.

Please let me know if you have any questions.

Mitchell

dchur

Hi @MitchellMc ,

Thanks. To be honest I'm not overly concerned about the colour so long as its functional. I wasn't too sure about applying a second layer but if that's an option I may just do that on the areas affected. The tube says 72 hours for a full cure so I'm guessing I can do it immediately after that after I ensure the area is dry etc?

MitchellMc

That's correct, @dchur.

The amount you have there currently appears to have fully sealed the gap. I do not believe additional silicone is needed for waterproofing. You could try another thin coat over the yellow section to see if it resolves that issue.

Mitchell

dchur

Thanks Mitch, will give it a go. Cheers

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