Cement stain on porcelain paving

Enty1989

Hi,
I was hoping somebody may be able to suggest something which can remove the light residue stain from the porcelain paving that has been installed? When it's wet you can't see the stain at all but it is visible when dried. 

I have already tried Bostik Cementone brick and patio cleaner twice and it's yet to remove it. The first time I tried with a 2 part water 1 part chemical mix and the second was as it says on the box (2 part chemical to 1 part water)

I'm assuming I may need to try something stronger but I'm unsure what. 

The grouting has not yet been done as I was hoping to clean the majority before grouting so that the grout doesn't dissolve away from any chemicals. 

Thanks for any help

grumbler

I don't see any stain, but normally they use hydrochloric acid to remove mortar stains - https://www.toolstation.com/bostik-concentrated-mortar-brick-cleaner/p98902

I guess any acid will do the job, try vinegar

Enty1989

Thanks, the stains are more obvious in person. The pattern on the paving makes it difficult to make out on the pictures but it's like a light grey/white haze on some of them.
That's the brick cleaner I've bought and tried but it hasn't worked. I might have to try a stronger mix and if not maybe try an alternative acid.
Thanks for your reply

Doozergirl

Porcelain is porous.  Rather than a stain, it's often product caught in the tiny little holes that you can't see until they get filled with something.  

This looks helpful, but I don't know how confident I'd be.  http://www.tileandstoneblog.co.uk/porcelain/how-do-i-get-the-grout-stain-out-of-my-porcelain-tiles/

FreeBear

grumbler said: I don't see any stain, but normally they use hydrochloric acid to remove mortar stains - https://www.toolstation.com/bostik-concentrated-mortar-brick-cleaner/p98902

I guess any acid will do the job, try vinegar

The Bostik cleaner is 10-20% hydrochloric acid - That should shift most staining. I've found a bottle labeled "Spirit of Salts" in a local supermarket. That is 38% hydrochloric acid   Surprised to see something that strong in a shop especially as the sale of other strong acids  to the public has been banned.

I doubt vinegar would be strong enough to do anything. Glacial acetic acid (super concentrated vinegar) might, but it is also flammable and not readily available.

Treat with extreme caution. Always add acid to water, and never the other way round. Wear goggle and marigold type rubber gloves when handling acids, and have a bucket of clean water to hand. A respirator is also advisable (preferably, a forced air one), as the fumes can/will damage your lungs.