Looking around the typical building you can see many examples of natural stone. For example in older homes there may be door steps, window sills, floors and even fireplaces that are made of stone (the author lives in a Victorian house that uses slate for doorsteps, window sills and even the coping on the wall in the porch). Modern homes may not have these features but could have natural stone worktops in the kitchen, and many office blocks and commercial buildings will have stone floors and may have stone facias.
As with anything, over time the surface of these areas will get dirty (most stone is porous and will absorb dust and other forms of dirt) and will need to be cleaned to restore it to its natural beauty – you can really see evidence of this in the big cities, where buildings like the natural history museum in London spend thousands to restore the stone to its natural beauty. While there are products on the market place that will allow the home owner to clean any stone they have in their home this can be a messy process and you can be dealing with some fairly nasty chemicals such as phosphoric acid (which is corrosive, and can be harmful if swallowed or gets in contact with you skin). We would suggest only using the cleaning materials that you can buy over the shelf (or online) for very small areas, making sure that the stone surface is not damaged in any way before you start and following the instructions to the letter (for example never mix acid based cleaners with bleach, doing so produces a gas that can be fatal if breathed in).
Of course, if you own a commercial building, be it a shop, office block or even somewhere like a museum, or if you live in a older (possibly listed) building that contains a lot of natural stone surfaces the “d-i-y” process is not really that suitable (especially so if the building is listed where there may be all sorts of conditions associated with repairs and maintenance) and you should employ professional stone cleaners to clean your stone for you. By doing this you know that not only will the job be done correctly (possibly using chemicals and processes that are not available to non-professionals) but that the end result will look much better than anything that you can achieve yourself. It is also worth bearing in mind the wide range of natural stone that can be used in a building, a product suitable for cleaning slate or granite, may damage the softer stones of sandstone or limestone, so make sure you read the instructions carefully to make sure you have the right product for the area you want to clean, and be especially careful with any products that claim they are suitable for all stone types.
Another area of natural stone that often needs cleaning is natural stone paving. If you have stone paving slabs in your garden you will know that it doesn’t take long before these look decidedly grubby and the temptation for many homeowners is to get the jet-wash out and clean them up. The problem with this is that although jetwashing natural stone does clean the stone it can also cause damage by blasting away the surface of the stone (softer sandstone is especially susceptible to this). Again, if you have a large area to clean it would be worth getting a quote from a professional natural stone cleaning company. They will be able to clean the stone safely and may even be able to seal the surface for you so that the stone stays cleaner longer.
Many professional cleaners are listed in the phonebook, or have websites detailing the area of the country they cover, the sort of projects they have worked on and the sorts of stone they can care for – it is worth spending some time looking at this information to help you identify the right company for your needs.