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Posted: Wed Jun 26, 2013 5:40 pm
by beige sawn
Our London Stone beige sawn sandstone was laid in November and sealed with Lithofin stain stop. The temperature was too cold and the sealant didn't seem to work, so we asked the contractor to reseal it in April. This was done, and an apparent seal was made.
The issue now is that the contractor did not effectively wipe away excess sealant which had been applied with a roller. We are left with 70-80% of the slabs having dark patches on them where this sealant excess has cured into the stone. Excuse my phrasing if I don't quite get how it works.
Anyway, the contractor has tried removing the patches with no success. the methods employed so far on a small area each time:
(i) stone cleaner
(ii) pressure hose
(iii) grinder with something like 40 grade abrasive disk. This looked like it worked but what actually happened is the very fine dust particles covered the patch and the rest of the stone, but when washed afterwards they washed away, and there was no real change in the appearance of the patch
We are at a loss as to how to remove the discolouration. It certainly doesn't look as if it is something which will disappear over time.
Any similar experience, or recommendations to solve?
here are some photos of one of the stains. Links, until I figure out how to make them appear in the post.
https://www.dropbox.com/s/4r9ug3nsdxdlu5q/IMG_0035.jpg
https://www.dropbox.com/s/x83zoqhfx4vmgro/IMG_0034.jpg
https://www.dropbox.com/s/g1f6on4on9v0byo/IMG_0033.jpg
images won't show 
Posted: Wed Jun 26, 2013 6:18 pm
by rimexboy
Posted: Wed Jun 26, 2013 7:15 pm
by lutonlagerlout
it looks a tidy installation
personally I would leave it and let the weather do its worst
if you continually attack it from different angles you run the risk of ruining it
IMHO
LLL
Posted: Thu Jun 27, 2013 8:24 am
by beige sawn
Yes, the installation prior to sealing was good as was the rest of the hard landscaping. No complaints from me in that regard. But though I have shown pictures of just one area the staining is present nearly everywhere so it is particularly noticeable. The spec for the sealant used indicates it is chemically effective for many years; it is unlikely weather is going to act on the patch areas at a different rate to the sealant elsewhere so that they become increasingly blended over time.
I was hoping someone may have solved a similar issue.
[thanks to the person making the photos show in line]
Posted: Thu Jun 27, 2013 8:29 am
by RAPressureWashing
You could most probably get the stains buffed out with a floor buffing machine. It is not something we do at present but I am looking at offering this service in the near future. I do know someone that does this and covers your area SW19, drop me an email if you would like his details.
Posted: Thu Jun 27, 2013 9:00 am
by beige sawn
We tried that on a small hidden section
At least, they used a buffing machine with some sort of 40 or 60 grade sandpaper on it. It created a lot of white dust, which eased into the surface of the stone making it look clean, until it was washed down and then no change to the sealant patch. Sealant is chemically cured deep into the stone, like it is supposed to be but just in an even layer.
Unless you meant something else rather than a device to "rub" off the marks
I'm wondering what London Stone think - it is their product?? I spoke on the phone any they pointed me to this forum on which I believe some of their experts reside.
Posted: Thu Jun 27, 2013 9:13 am
by RAPressureWashing
beige sawn wrote:We tried that on a small hidden section
At least, they used a buffing machine with some sort of 40 or 60 grade sandpaper on it. It created a lot of white dust, which eased into the surface of the stone making it look clean, until it was washed down and then no change to the sealant patch. Sealant is chemically cured deep into the stone, like it is supposed to be but just in an even layer.
Unless you meant something else rather than a device to "rub" off the marks
I'm wondering what London Stone think - it is their product?? I spoke on the phone any they pointed me to this forum on which I believe some of their experts reside.
Yes I did mean something else and not with "sandpaper"
I do understand how sealers work and unfortunately you have had someone who hasn't applied the Lithofin properly.
I don't feel it is a failure on London Stones part or the product, it is how it was applied that is the issue, IMO.
Posted: Thu Jun 27, 2013 10:45 am
by beige sawn
OK sorry I wasn't trying to question you, I guess I'm just trying to understand the terminology. I also wanted to know if London Stone had any observations; again if it looked like I was implicating them this isn't what I was trying to achieve. It seems pretty clear the application of the sealant was the problem.
R&A I will contact you directly if the next round of efforts are unsuccessful.
Thanks
Posted: Thu Jun 27, 2013 12:43 pm
by Bec@LondonStone
I would agree with Roger, buffing is the way forward or perhaps try to use some emulsifying pads to remove the excess. I wouldn't worry too much, if the problem is excess sealant then it is fixable. Roger - am I right in thinking that you can sometimes use a little of the original sealant along with an emulsifying pad to try and remove excess? Is this worth a go do you think?
Posted: Thu Jun 27, 2013 3:34 pm
by RAPressureWashing
Bec@LondonStone wrote:I would agree with Roger, buffing is the way forward or perhaps try to use some emulsifying pads to remove the excess. I wouldn't worry too much, if the problem is excess sealant then it is fixable. Roger - am I right in thinking that you can sometimes use a little of the original sealant along with an emulsifying pad to try and remove excess? Is this worth a go do you think?
You are along the right line of thinking there, but the sealer has been down since April, so might be to set/cured for this to work, always worth a try though. Because it is just excess sealer it should buff out, along with a sealant remover.
I'd go along the lines of cleaning the whole surface with a light sealant remover to remove all excess mark/stains by doing the whole paving area you will balance it all up, then re-clean with some honing powder added to cleaning mix, all done with a rotary cleaner, allow to dry etc the re-seal.
Beige Sawn, no offence taken I was just trying to guide you in the right direction.
