bad marks on stone

[jonnyc]

just started a new job with a mandarin stone 500x random .
cant remember the name .
Darren ( freeze) do you recognise this one.Ive been put on their recommended list for weybridge!!!
stone beautifully cut square and even thickness.
client received stone a month ago and brought in to house and stacked the tiles slightly offset on top each other so that they were easy to pick up.
when bringing stone in to area to be tiled can see that the parts of the tiles that were exposed to air and sunlight have changed colour.
this is clearly visible on photos.
any ideas about how to get rid of these marks or what causes them
having flagged them up i have been asked to fix regardless in the belief of client that what was hidden from light / air will change colour when exposed and fixed .
i ve thrown the whole innards of cleaners in my van and wont touch it nd wont touch it

 

[Chalker]

Is it staining or moisture?

 

[jonnyc]

the marks are just corners of stone that have been open to elements inside and daylight

 

[One Day]

I may be wrong (often am) but I thought this kind of staining was trapped moisture.
Have you left a stained piece in a warm enviro for 48hrs?

I've seen it on trav and it has vanished overnight indoors once they were unstacked.

 

[Concrete guy]

It looks like a light seam of Azul Valverde to me. In which case it will be pretty dense stuff for limestone.

It will probably be moisture differences causing the issue and it's unlikely you'd be able to "clean" it.

 

[Chalker]

Has the property got underfloor heating? If the floor is drying it will deposit the moisture to anything absorbent.

 

[Colour Republic]

The stone has been dyed has it to make it more desirable? And now faded in sunlight? Not from china is it?

other than that probably is moisture

 

[jonnyc]

The stone has been dyed has it to make it more desirable? And now faded in sunlight? Not from china is it?

other than that probably is moisture

No not been dyed but interesting possibility.i have come across this with Paris ceramics in the past

 

[jonnyc]

It looks like a light seam of Azul Valverde to me. In which case it will be pretty dense stuff for limestone.

It will probably be moisture differences causing the issue and it's unlikely you'd be able to "clean" it.

Sorry don't understand

 

[One Day]

Sorry don't understand

What I said but cleverererer!

 

[Concrete guy]

Sorry don't understand

Assuming no one has done anything dumb here like presealing and stacking.

The exposed bits have dried at a different rate to the non exposed bits.

Don't mess around with chemicals, it won't make a blind bit of difference.

Stick a tile in an airing cupboard for a day or two and see if its appearance changes.

 

[jonnyc]

You will notice that the edges that were exposed are darker than the parts of stone that were covered.you would expect this to be reverse way round.if there were any moisture in stone it would be in the middle sections .put a hair dryer on the stones makes no difference .
tried wexa,wax off ,outdoor cleaner and oxy clean crystals but none work.ii have had this before when exposed edges of tiles in a crate are left outside.
always seems to happen with grey stones.something to do with oxidation?

 

[Concrete guy]

i have had this before when exposed edges of tiles in a crate are left outside.
always seems to happen with grey stones.something to do with oxidation?

If this is a dense as I think it is, which dark limestones tend to be, a hair dryer wouldn't make any noticeable difference.

Oxidation is possible, if it is that I'm not sure how you'd chemically deal with it. It would probably require re honing. Or as the rest of the stone is exposed for a month it would create the same patina, but then you'd need to leave it unsealed for a month.

Call Mandarin, see if it's known problem with this product.

It almost reminds me of Mexican Saltillo when it was stacked to dry you'd get distinct patches of light and dark, which in that case was UV light bleaching. What you have though is the reverse, which is odd.

 

[jonnyc]

It's called Blenheim by mandarin.i checked stone with damp meter and dry.its lightly brushed so can't be re honed.
had a similar problem with Jura grey few years back when builder covered floor with cordex over building card for whole winter with heating on.it sweated and left brown zebra stripes on floor . Could not get out chemically and had to grind and repolishing whole floor.
client is convinced it will even up but I'm not sure

 

[Qwerty]

I've had similar happen and in my case it was dust from the builders that had settled on it in a damp atmosphere and almost appeared to etch itself onto the tile. Mine came out with cleaners though, so a bit stumped in your case!