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How to clean black specks in tile grout?

Hi folks,

Has anyone come across this before? While cleaning the shower I noticed small black specks throughout sections of the grout on the shower floor tiles. I tried mould killer, grout cleaner, a bristle brush, and steel wool but nothing seems to get rid of it. There are very small sections of this all around the shower floor, with one main section in the middle of the shower (shown in the photo).

I can't see any water damage anywhere and the tiles don't sound hollow or seem to be lifting. I'm considering applying some rejuvenation grout over the top, but really curious what has caused this. Thanks in advance!

Cheers,

Rhys

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Accepted answers

MitchellMc

Welcome to the Bunnings Workshop community @rhys09. It's wonderful to have you join us, and many thanks for your question about grout.

It looks like a very coarse grout was used, containing darker granules of aggregate — almost like a construction-grade grout. When it was first applied, the water in the mix likely caused the finer particles and colourant to rise to the surface, giving a more uniform appearance. This is called laitence. Over time, that fine coating has worn away, revealing the darker, larger aggregate particles beneath. Lighter-coloured grouts often have this effect because the binder is light, but the aggregate can be quite dark.

Applying a rejuvenation grout sounds like a good approach here, especially since the existing grout is set low between the tiles and gives you plenty of height to work with.

Here's a helpful guide: How to grout tiles.

Please let me know if you have any questions.

Mitchell

All comments

MitchellMc

Applying a rejuvenation grout sounds like a good approach here, especially since the existing grout is set low between the tiles and gives you plenty of height to work with.

Here's a helpful guide: How to grout tiles.

Please let me know if you have any questions.

Mitchell

rhys09

Great thanks for that @MitchellMc, much appreciated!

Do you happen to know if Bunnings sells smaller sizes of the rejuvenation grout? Don't think I'll be needing the full 1.7kg tub.

I did a quick search on the website and the Davco 1.7kg is the only one showing up. But maybe I'm just using bad search terms or it's called something else.

Cheers,

Rhys

EricL

Hello @rhys09

The Davco 1.7kg Rejuvenation Grout - Picket Fence only comes in that size. The issue with using other grout products is that it requires you to remove all the grout from the affected area and reapplying the grout line in full. If you were to go in that direction, I suggest looking at the Dunlop 800g Ready-To-Go Coloured Grout.

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

Eric

rhys09

No worries, thanks @EricL

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