Staining on pietra serena sandstone

[jonnyc]

JUST LAID A PIETRA SERENA SANDSTONE FLOOR IN A KITCHEN.
IT WAS PRESEALED THREE TIMES WITH STAINSTOP BY A DRYING AND SEALING COMPANY, SO STONE WAS DRY WHEN SEALED.
LAID STONE IN PCI CARRAMINT ADHESIVE WHICH IS RAPID SET WITH NEW LOCK IN MOISTURE TECHNOLOGY SO NOTHING MIGRATES THROUGH STONE TO SURFACE.
SO FAR SO GOOD.
WANTED TO GROUT STONE WITH GROUT THAT HAD NO ADDITIVE BUT COLOUR WAS NOT APPROVED.
INSTEAD HAD TO GROUT WITH ARDEX FS CAST IRON AND DOVE GREY PROPORTIONALLY MIXED TO APPROVED COLOUR.
DID SWISS DOUBLE GROUTING , COVERING WHOLE FACE OF TILE FIRST TIME AND ONLY JOINTS SECOND TIME TO MAKLE FLUSH.

FLOOR WAS VERY WELL WASHED AND ALL LOOKED EVEN.
CAME BACK NEXT DAY AND THERE IS 50-70 MM WIDE DARK STRIP EACH SIDE OF JOINT.
DOESNT LOOK OR FEEL LIKE GROUT STAIN SO THOUGHT IT COULD BE MOISTURE WORKED IN TO FACE OF TILE WHEN GROUTING.
THIS STONE WAS STILL A BIT POROUS EVEN THOUGH PRESEALED THREE TIMES.
SO LEFT FLOOR A WEEK AND CAME BACK YESTERDAY TO SEE IF HAD CHANGED.
STILL THE SAME.
SO APPLIED POWER CLEAN IN CASE GROUT RESIDUE AND SCRUBBED. DRIED TILE WITH HAIR DRYER BUT STAIN STILL THERE.
I WILL GO BACK WITH DAMP METER BUT NOW WORRIED THAT STONE HAS STAINED.
I HAVE ALSO PLACED A STONE NOT FIXED NEXT TO FIXED STONE AND IT IS MUCH LIGHTER IN COLOUR EVEN LIGHTER THAN THAN MIDDLE OF FIXED STONE THAT HAD ONLY ONE LOT OF GROUT ON IT.
STRANGe THING IS THAT HAVE TRIED GROUTING OVEDR FACE OF A LOOSE TILE YESTERDAY. LEFT FOR 30MINS AND WASHED OFF .
DRIED IN SUN AND NO STAINING AT ALL.
.
THIS DOES NOT LOOK LIKE THE NORMAL INGRESS OF MOISTURE THROUGH SIDE OF TILE (ie picture framing) WHICH YOU CAN GET WHEN GROUTING ASTONE THAT HAS ONLY HAD WATER BASED SEAL APPLIED.
WHEN THIS HAPPENS , IF LEFT A FEW DAYS PICTURE FRAME CAN EASILY BE REMOVED WITH WEXA SCRUB.

PIETRA SERENA IS NOTORIOUSLY TEMPERAMENTAL BUT I HAVE TAKEN EVERY PRECAUTION COULD THINK OF WHILST FIXING.

ANYONE GOT ANY IDEAS HOW TO GET RID OF MARKS

 

[Perry]

i don't know the grout but it should be rapid setting because the water goes into the stone from the grout and because you have sealed the stone water can only come back through the joint could take months is why i always tried to use sand & cemet

 

[Spud]

Fs is a rapid setting grout pete I think the problem Jonny is the method you grouted from what you describe as swiss grouting I know as flood grouting where by the first grout mix is wetted right out and then dry grout powder is blinded down the joint to flush them with the top of the tile, grouting in this way would have locked the moisture under the tile thats normally fine if you have mortar bedded the tiles as the sand and cement soaks up the excess moisture and the tiles dry out evenly but with adhesive it doesnt soak the water up so well

 

[Perry]

i use sand and cement as grout lol

 

[Perry]

in fact years ago before rapid grouts we used to grout limestone before we sealed it as well :yikes: and still do with trav

 

[jonnyc]

ardex fs is normal set i think. only fl is rapid set.
swiss grouting is a term used by the swiss strangely enough, which i learnt in switzerland. this method may well be used elsewhere under a different name( THE GRIMSBY DOUBLE MAYBE , BUT DONT THINK THEYVE EVER DONE A DOUBLE OF ANYTHING I KNOW OF, EXCEPT DOUBLE DIAMOND.) but i had never come across it in uk many years ago.
The swiss used to double grout marble and granite twice. first time could be a bit wetter than you might normally do but not a real slurry. the idea was to fill most of the joint up but dont worry too much as the second grout pass will sort any uneveness out.
they would clean off tile fairly quickly as didnt need grout to be hard enough to get flush. apply second coat drier but only like normal grout and definitely before the first grout had hardened or dried.
because most of joint full already from first pass and something for second layer to bond to , could achive a very flush joint when second coat cleaned off.
I have discussed this method with ardex and mapei in past and they have no problem with this method. just dont do first grout let it dry and skim over with last coat.
fast forward to porcelain and limestone in recent years.
re porcelain we all know how difficult it is to get a really flush joint on rectified porcelain.this method works perfectly to fill joint up. ok can get a good result with polmer modified fast set mapei grout or similar but here lies the problem .
some of these single part flex grouts are just too sticky for some limestones and sandstones.
I know there are special grouts out now from ardex and others for stone but they will still stain an open pored limestone like bath stone,lincoln and the dreaded sandstone.
As any experienced stone fixer will say , with exception of travertine that you can grout unsealed without picture framing and a few other stones, IT IS ABSOLUTELY IMPERATIVE THAT THE WHOLE OF THE FACE OF STONE IS COVERED BY GROUT AS OTHERWISE WITH OPEN STONES YOU WILL GET A BAND SHOWING UP ON EITHER SIDE OF GROUT JOINT.
This is not moisture picture framing but just grout getting stuck in tiny pores where squeegee has been applied around edges of tile only. If you have grouted the whole face first time you would not see anything or even know how grout has picked up and changed colour of stone.
So how have i still got a problem when i have taken every precaution i can think of .
this is why i am stumped especially after leaving single part flex grout on a spare pesealed tile for half an hour and managed to clean off with no staining at all!!
ANYONE OUT THERE WITH LOADS OF PIETRA SERENA EXPERIENCE AS I FEEL THEY WILL HAVE THE ANSWER.

 

[Spud]

Did you grout it Jonny or was it done by someone who works for you ?

 

[Perry]

i have seen it many times mainly on honed limestone when it has been sealed first but have seen the same stone grouted first with no problem

 

[jonnyc]

grouting done by one of my employeees, but he has had 12 years practice so dont think this is problem. he is as bemused as i am

 

[Spud]

Hi Jonny i done some reading on this sandstone and I read that it can have iron deposits in the stone which can oxidise does the staining look like a rusty colour

 

[jonnyc]

gary thanks for taking trouble to look this up.
youre right this staone does change colour over time but would not go this dark.
I had a green chinese sandstone last year which i laid inside, which did take on a rusty colour after few months, and the view then was it was oxidation.
also had same problem with jura grey but the colour change is so very slow so would not really notice it happening.

this serena stone discoloured as soon as grouted all over tile and then another wide darge band around all four edges.
i am still stumped by this.

 

[jonnyc]

Just sorted out staining problem.

I had come to conclusion yesterday that the staining was some kind of grout residu haze on stone as numerous cleaning pruducts had not worked.
I really wanted to use a cement residue remover but was worried that it might attack face of sandstone.
But i have run out of time with handover.
So did test on loose bit of stone with something called brickie.
It is not like the usual cement remover with the normal hydroclauric acid.
Anyway did a test on one tile and all the marks came clean off, so can now clean whole floor with scrubbing machine.

Result.