Stone Cleaning

[mike.m]

  A white van man who was spraying the neighbours roof for moss prevention called over to see if we were interested and seemed surprised when we declined his offer of  2000 euros for a day on a ladder with a garden spray .

     However he changed tack and pointed to the stains on the outside walls which I'd taken to be humidity (dark staining on the natural  stone,  render and reconstituted stone which he said were champignon.) He offered a free demo . ,went back to his van and returned with a second plastic low pressure spray and proceeded to drizzle this clear liquid on several affected areas . Magically, within minutes they were restored to pristine condition . Despite this his offer of another 1000 euros was unpersuasive and naturally he wouldn't comment on what the product contained , just that it was professional gear only available to artisans .

                                                  I would dearly love to track down what he was using as it was very effective ; I can only add that when I tried to touch the wet surface he told me it was dangerous and  I noticed a smell a bit like chlorine .

                  Any Sherlocks with suggestions about the mystery liquid and where it can be bought ?

[Albert the InfoGipsy]

Try eau de javel.

http://www.completefrance.com/cs/forums/1135096/ShowPost.aspx

Failing that, look around the bricos.

[timc17]

We also use eau de javel and it's very effective. Please be careful as it will burn anything. We tend to get togged-up like spacemen if we've a big area to do.

[mike.m]

Thanks to both ; have tried the javel and its not really working ; certainly not the same product as the snake -oil which had an instant result . Chatted with the sales people in Castorama and they knew about the stuff but didnt know either what it was called or where to obtain it . Suggested I call the white-van man and offered to buy the product from him which I may do as a last resort . Further insights welcome?

[Gardian]

White van '62' registered?

Dodgy, I'd say.  Turn up here every couple of yrs.  Wide boys - best avoided.

[Lomelec]

We used an hydrochloric acid based brick cleaner to clean up a stone wall quite successfully earlier this year. It fizzes when you apply it with a paintbrush and you then hose it down with plenty of water 30 minutes later. It came from B&Q in the UK - their own brand. It took off the top surface of the stone and joints along with virtually all of the motar staining. Some lime staining still remains and we're going to give it another clean this summer to hopefully remove the rest of it. We were a bit worried about it running down the wall and dissolving the concerete floor so we laid down a plastic sheet, but it seemed to lose it's initial potency within a few seconds of applying, and it tended to soak in rather than run down.  

Dressing up in protective gear was almost as much fun as applying it!