Patchy colour with Mapei grout

[Dylan T]

Hi all - I've just done a DIY tiling job on new tiles using Mapei medium grey grout ultracolor 112 for the grout. I've used Mapei Ultracolor for loads of projects but never that exact shade, but have never had a problem before. Frustratingly it's dried with really inconsistent colour with some really dark patches. Next to those patches it seems really light so I'm assuming the pigment has for some reason separated out. I didn't mix mechanically as only a small pack, but I did mix it for ages by hand, and it's nothing different to what ive done every other time. After some quick reading online it seems that other people have had issues with this particular shade so I'm wondering if something is up with it? It'd be great to know some suggestions of what's gone wrong, but at either rate I need to sort it and really don't fancy raking it all out. I'm considering trying a light top up with another go; risky of flaking too high?

Thanks

 

[Swwils]

Ultracolour plus is has a "self-hydrating-hydraulic binder" that ensures the colour uniformity. Its very important that substrates are sufficiently dry or have been waterproofed, to avoid a whitish film forming on the surface. In theory it should never get any staining like this because its not portland-cement based binder in it. (To get technical; the cements in ultracolour plus do not generate the calcium hydroxide (hydrolysis lime / portlandite) crystals which cause efflorescence during the hydration process).

Along those lines: it must not be mixed with gypsum or other hydraulic binders; and never add water to the mix once it has started to set!

Also in general:

1. The tile adhesive needs to be completely set
2. Joints need to be clean, free of dust and any adhesive or mortar that squeezed out and should have been removed whilst fresh.
3. Mix it up only with clean water, not salty or dirty water (maybe you have a salt water softener?)
4. When you mix avoid air entrainment, so mix slowly.
5. Don't do that thing some people do where they sprinkle into the filled joints

Use two buckets for finishing, one to get rid of the excess mix from your sponge, the other with clean water to rinse the sponge. The secret to a great finish is the correct hard sponge for the job.

If for some reason where you are grouting is hot then dampen the joints after a few hours. Unfortunately 112 grey is just a shade that will show any issues very clearly.

You really need 2/3 tile depth to grout properly, take the time to do it right.

Let me know what you think; I hope this helps, good luck!

 

[swaring]

I’ve had the same with my outdoor porcelain slabs. Manhattan grey I used. I followed instructions exactly. Had a technical person come out and then analysed it to no explanation. Basically I have come to the resolution Mapei is crap in lighter colours. Basically had to grind it all out and use aspects grout, with no problem at all.