Black limestone - grouting stains

[janz70]

Hi all,

we have just had 55m2 of black limestone laid and while most of the joints are ok, some (that the labour did while the paver was laying a section of stone) have turned out quite bad, staining the surrounding stone. Obviously he didnt clean as he went but what can be done to remove this?

Ive been over it a few times with the Karcher patio cleaner which has cleaned up the main surface of the tiles but just cant get the edges clean on the bad bits.

I contacted the guy who laid them and he suggested a brick / mortar cleaner!!!!!! - I told him in no circumstances was he to use an acid cleaner on this limestone (after reading up on here it saved my patio)

I was wondering if a weak solution of caustic soda would be effective as it is alkaline like the stone. Anybody tried this out in the past?

PS A 2:1 mix of building sand and castle OPC was used for the joints, almost a dry mix pushed in with a pointing tool

[London Stone Paving]

You were right not to use a brick/mortar cleaner. I have not got any experience of using the substance that you mention. Test it out on a small inconspicuous are first and see if there are any adverse effects

[janz70]

Hi, Sorry about delay in my reply, I couldnt log on for last few days due to probs with the website.

Its a shame about the picture framing effect (if thats the correct term) as it looks great when damped down - I have the sealer ready to go but what with the weather and this staining its looking unlikely I'll get it sealed before winter unless we have a freak hot spell.

Can you recommend other products that you have used with success in removing mortar stains in the past if this doesnt work?

[RAPressureWashing]

Can't see the caustic soda working sorry, plus unless you know what you are doing caustic soda can be very dangerous to use, as it becomes unstable when you start adding water, believe me I have had it blow when trying to make a hot mix.
it will remove paint, some oils etc but not mortar stains?
Can you post a photo of the staining and let's see if there is another route.

[janz70]

Hi, hopefully doing this right



Efflorescence in photo 2 and 3?????

[janz70]

Photo 2 and 3 (above post) are of an area laid on the day after the torrential 24 hour downpour on Friday last week - its looks milky but under surface no powder on top and wont brush or hose away

when its wet the patio looks like this







PS I work in the chemical industry so Im used to using chemicals but a word of warning/advice never add water to Acid or Alkaline add them to water or you will get the reaction you did

[lutonlagerlout]

apart from the stains that looks a tidy job
LLL

[RAPressureWashing]

Is this something you want to do yourself or have someone come in and clean for you?
Let me know and I can point you in the right direction either way?

PS it wasn't the mixing stage that caused the problem, a hose from the low pressure supply pump got a kink-in it, causing it to let go.

[janz70]

Hi, would prefer to do it myself if possible to keep cost down

[RAPressureWashing]

Hi, would prefer to do it myself if possible to keep cost down

Give this company a call,
http://www.tilinglogistics.co.uk

The guy to speak to is Kevin Martin, he will have all you need to do this work yourself, let him know you have spoken to me, he might want you to send photos of the area so he can cost the products needed.
You will need to let him know what equipment you will be using etc.

[janz70]

I'll give him a bell, thanks for the info

John