Grout Efflorescence problem on black grout

[Lithofin BOB]

Please Do not use cement away , this is an exterior only product -hydrochloric acid will cause you much more problems than grey black grout. I would stay away from anything acidic, as This can also whiten the resin in an aglomerate tile. You could test a light alkaline product , we have power clean ( others makes avalible ) and a white pad , as Julian , you will be lucky to get this back. Have you had a test scrape, is the black colour under the surface, if not - cleaning won't help here.
Could you use a grout revival product on it, other than rake it out

 

[J K Tiling Cornwall]

Hi Craig,
Efflorescence on the surface of the grout
Joints can be more of a problem with non porous tiles as adhesives and grout have longer drying times. I think the tiles you mention may be a composite (Stone resin) did they have a fibre glass resin smell when cut on the wetsaw? Have had before and it does clear with time and wiping down (the adhesive may still not be fully cured) would avoid any acids or strong chemicals just yet, would advise testing on a off cut first. As a last resort Mapei do a colourant, but have not used myself. Hope this helps.
James.

 

[Craig Blick]

Hi Craig,
Efflorescence on the surface of the grout
Joints can be more of a problem with non porous tiles as adhesives and grout have longer drying times. I think the tiles you mention may be a composite (Stone resin) did they have a fibre glass resin smell when cut on the wetsaw? Have had before and it does clear with time and wiping down (the adhesive may still not be fully cured) would avoid any acids or strong chemicals just yet, would advise testing on a off cut first. As a last resort Mapei do a colourant, but have not used myself. Hope this helps.
James.

Thanks for reply james I'll give the colourant a go as rather not ruin tiles, yeah they did have that kind of resin smell when cut do ill avoid acid for now cheers

 

[Craig Blick]

Please Do not use cement away , this is an exterior only product -hydrochloric acid will cause you much more problems than grey black grout. I would stay away from anything acidic, as This can also whiten the resin in an aglomerate tile. You could test a light alkaline product , we have power clean ( others makes avalible ) and a white pad , as Julian , you will be lucky to get this back. Have you had a test scrape, is the black colour under the surface, if not - cleaning won't help here.
Could you use a grout revival product on it, other than rake it out

Hi could you recommend the best product you offer for this problem? Cheers

 

[Dumbo]

Hi could you recommend the best product you offer for this problem? Cheers

He did . Power clean

 

[Lithofin BOB]

As James, test your cleaner on an off cut, did you have a test small scrape at the surface to see if the original colour is there.