staining on honed slate

[bennyp5938]

Hi guys,

got some stains appeared on some joints (not all) on honed grey slate (600x400).(see attached pic). clean water was used to wash when fixing and bal rapidset flexi was used to fix. the stone is fixed but not sealed or grouted yet. I thought maybe the staining could be removed when washed with grimex prior to sealing and grouting?? (not tried this yet)
any ideas on causes and solutions?

Thanks

 

[peteablard]

How long ago were they fixed?

 

[bennyp5938]

They've been fixed for 5 days. Its a new build. No heating etc.

 

[afright]

To me it look,s like they may have been stained thru you washing them and water has built up in the joint,s and has laid there while the surface water has dried, the water in the joints has slowly dried causing the stain

 

[Tony73]

some stone is better to seal before fixing. This stone in your picture, should be dryed and sealed before fixing. Some high polished marble could be sealed before grouting. If tiles are still damp, sometimes we use blow torch to dry them. When applying stain stop on tiles, apply on face and all four sides.