[gwrightson]

Al ittle help in what your opinion would be best to remove this reidule from vents on a home, the wents are on the roofsand are from wood and oil burners installed in the house, the stone i have yet to find out exactly what it is as the owners are not back from holiday untill toomorow, i do know the stone was imported from Italy for the build , and i do know pressure washing alone will not remove. i wil try to attach some pics.
Price is not an issue.

Geo 
ff

[gwrightson]

IMG]http://i43.tinypic.com/ofys78.jpg[/IMG]


there are 7 vents in total so 7 areas to be cleaned .

Geoff

[gwrightson]

[Matt Gibson]

Looks like sandstone to me. id try a hydrofluoric acid on it but do a test somehwere as ive had some sandstone discolour using the acid. Some other sandstone ive used it on has been fine. and make sure u have full ppe cause its nasty nasty stuff.

[M W.]

cleaned similar staining on a harder surface with hydrofloric acid based chem with
very satisfying results. take matt,s advice with the ppe, its a very naughty kem.

[BDCS]

I'd try wet blast with soda first and if that fails resort to the chemicals

[gwrightson]

 Tks forn reply guys,   i will try the acid route , i am guessing brush on rinse off, !!!!


Geoff

[trevor perry]

i would find out what kind of surface it is before using any kind of acid, or if you cant identify the surface then only try acid in a small inconspicuos area first.

[gwrightson]

Yes Trevor, i will be talking to the owners in the next day or two, after they have spoken to the architects for exact type, having spent a few hours doing a little research ,i think i will go down the soda blasting route to start. appears much safer for starters, next task find some body who hires a soda blaster out !

Geoff

[BDCS]

I have a soda blaster but why can't you wet blast it ?

[gwrightson]

 I did  a  test with water , result was ok , but not perfect and the risk of damadge to surface was too high, the house alone cost £12 million to build , so erring on caution .

Geoff

[Kev Martin]

Personally  looking at the pictures it looks like mechanically fixed stone cladding.  Because of this, subject to doing a test area I would pre wet it and clean it with a soft to medium rotary brush and some high alkaline cleaner then rinse it with clean water I would not use any high pressure or blasting of any sort.  I would also advise the client and recommend sealing it with a Premium water based penetrating sealer to make future maintenance easier.

Kev Martin
Marble Life Ltd

[gwrightson]

Kevin, as far as i was made aware the stone it self was quarried in italy , cut to size as required by architects , numbered in order of placment on the build, thanks for your imput ,i will of course be looking at all options.
geoff

[Kev Martin]

As a matter of interest where is the job?  I am not trying to pull one over on you but it looks like a few other jobs I have handled!!!  Is there a lady called Francesca involved per chance because that stone looks like it is from her fathers quarry

Kev Martin
Marble Life Ltd

[gwrightson]

Kevin,  No not called francesca 
The house is in Yorkshire and is only 3 years old , i will try to find out more details today of exactly which quarry, etc  . 
Geoff

[John Kelly]

Geoff thats very similar damage to a fire job I recently done. There were cut sandstone blocks over the door and window archways. We used our Tornado alkaline cleaner which took the bulk off but not all. The lad working with me used to be a stone mason so he showed me a trick they used to use. You get a flat peice of similar or softer stone and after wetting the surface just rub away with the flat peice of stone. It came up mint and client was delighted as he had spent a great deal of time and money sourcing this stone. This was a new build holiday home which caught fire just before completion.