How to remove black discolouring from stonework?

[Jane Smith]

We live in a Victorian stone house on the moors just outside Sheffield.

The stonework is very dark and discoloured, and we were wondering if there was any way to remove this blackening without resorting to sandblasting which is a very heavy-handed way of proceeding.

Does anyone know if there's any product which would dissolve the black discolouring? Or does anyone know what the black stuff is?

Thank you!

 

[Jane Smith]

I don't know how this will work here: this should either give you a link to see a picture of the front of our house in all its blackness or it might actually load the picture here. Goodness knows. Hope it works one way or another.

http://i76.photobucket.com/albums/j26/Guineaqueen/SundayTimessmall.jpg

 

[Gervase]

The black stuff is a mixture of lichen, soot and sulphides - a ghostly reminder of Sheffield's industrial past.
Sandblasting isn't a good idea, but there are other methods. Most of the companies working in this field use kit supplied by Stonehealth and seems to have been used on a number of sensitive projects without causing damage. Such treatments aren't cheap, though!

 

[Ian Bond]

Just wondering if the pollution is likely to be causing damage to the stone, or accelerating the erosion of it?

I'm in 2 minds about stone cleaning. One the one hand I like fact that it looks old, and bears the marks of time and industry. On the other hand, perhaps careful cleaning would be kinder to the stone in the long term?

 

[jthurlbeck]

This is a relativley simple procedure and can be one fairly cost effectivley. Please look at this brochure, this will give you some information on cleaning the building but also protecting the stone once it has been cleaned. If you need a specialsi contractor i can put you in touch with some one, just e-mail me on jont@remmers.co.uk

http://www.remmers.co.uk/downloads/stonerestoration.pdf.pdf