Inconsistent grout colour

[jobdone]

Recently tiled a bathroom 500 x 200 ceramic tiles onto drylined and tanked walls(Ardex tanking). The adhesive used was webber spf rapid set. The problem is the grout colour is very inconsistent. The grout used was Ardex slate grey FS 3mm joint. the grout is almost black in some areas and very light grey with in a few hundred mm. The walls have been allowed to cure and have been washed down twice with Lithofin cement residue remover.
The effervescence has been removed but the problem persists.
Ardex have not been much help and i am at a loss as how to rectify the problem and appease my customer.
Any advise or suggestions will be gratefully recieved.

Many thanks in advance

 

[cam_low]

Grout stain from trade tiler

 

[White Room]

How long has the grout had to dry....

 

[jobdone]

the grout had about 2 weeks before it was washed the first time then a further 3 weeks before washing the second time. It has been around 8 weeks now and no improvement.

 

[jobdone]

i have never used the grout stain is it easy to use?

 

[Sean Kelly]

Just paint it on with a tooth brush. It will save the day. I have only used Aquamix grout colorant.

 

[Lithofin BOB]

Did you use stated water to powder, if not the powder may have not hydrated correctly leaving areas of darker patches, or if you over watered this can also leave patches and efflorescence , test the grout stain as this can often darken all the grout and the patches ,so can still stand out as it darkens them to. ( worth a try)The acidic cleaner may not touch these as the can be the often the depth of the grout and will not simply clean away.

 

[nybor62]

maybe im just lucky , but iv'e never had probs with grouts drying diff colour . and cant think why it should , i mix the grout the way i like it ,

 

[Lithofin BOB]

Think it may be the darker ones generally get 3-4 of these a week,

May have greater impact if the tile is textured and the amount of cleaning to Remove grout and poss over wetting at this stage leaving patches also

 

[Lithofin BOB]

Just a thought, if you were to mix a very wet slurry with initial grout and it's pigment, sponge over grout would this be enough to re- darken grout evenly - or would this not set and just wash out