chinese green sandstone

[jonnyc]

just fixed a chinese honed green sanstone floor inside @180 sq mts.
used stainstop mn. two coats before grouting and one after.
floor looked great and client happy.
then client complains still staining and difficult to mop despite using 1 litre per 5 sq mts.
very open pored stone.
asked me to apply more mn stainstop even though well sealed and had suggested multiseal as a top coat to help fill in pores on surface.
applied a further 16 litres over whole area and this last coat of 16 litres over 180 sq mts has left marks all over stone.
sealer soaked in after 10 mins and no residue left on top apart from few spots that i rubbed off with stockinette within that time.
There was no evidence of any dirt on floor when i was sealing and cloth showed no discernable discolouration.
I have never had a problem with stainstop before and maybe it is dirt in stone from time i first sealed stone.I really dont know, quite a mystery.
has anyone found stainstop to discolour sandstone unevenly or maybe found there is a some type of mineral/colourant that comes out of chinese sanstone.
stainstop is the most user friendly product to use over all other limestones i have found and have literally laid and sealed a minimum thousand floors with no problems and also cleaned and reasealed other floors not laid by me without any problem with stainstop mn.
I guess i am looking for someone who has laid chinese green sandstone
to find out if they have had similar problems.
I got over he problems of it not being square and flat it is just the sealing issue.
I was intending to put multiseal on top of stainstop having scrubbed floor to get rid of surface tension so it would adhere but have not got that far yet.
Multiseal if it does not streak would give the floor a ilky feel and easier to mop i think.
any advise would be greatly appreciated.

 

[DHTiling]

The thing is w ith some sandstones is that they do still grab surface muck...Impregnators are great for stains but will not stop surface grime...

As you say a topical sealer will aid in the cleaning as you know it lies on the top ...but will need replacing more often..

As for the staining as you seal....all i can think of is bleeding from minerals as more stainstop is soaking in....

I have used as much as 6 to 7 coats on very porous stones..

Have you any pics..?

 

[jonnyc]

will take some pictures tomorrow.
I too am thinking it may be something to do with salts/minerals working out through stone.
Will never do this type of stone again.
I have laid six sided sawn york many times in side and out without any stain problem when sealing and grouting although always suscepitible to staining afterwards.
Also laid saudi sanstone polished palnks with no problem staining only problem was them bowing when drying if not laid in fast set and weighed down when drying .