When we think about stone, most of us see a solid object that will last the test of time without deteriorating. However, all natural stone contains multiple tiny capillary channels, which allow penetration by fluids and gases. Over time, these channels work like a sponge, drawing in liquids through the tiny capillaries, along with whatever minerals and salts are dissolved in the liquid. Granite is very dense, so this occurs very slowly, while rocks like sandstone, which are highly porous, absorb water much faster. We use a range of different stones around our homes for Kitchen floors, bathroom tiles, driveways and to provide decoration in the form of statues.
What damage can happen to stone?
The most common form of damage to stone is staining. It is the result of liquids penetrating the capillary channels and leaving mineral deposits that cannot be removed without destroying the stone. Any type of acid, even that found in our rain, can damage the stone. Calcites in stone such as marble or limestone react with the acid, eventually eroding the stone, leaving dull marks on previously polished surfaces. While these are processes that with mild acid take time, any contact with stronger acids, as in an accidental spill, can cause irreversible damage very quickly. Something else we see on a far faster basis is the growth of moss, algae and bacteria, which cover and stain the surface. In places that see sub-zero temperatures, frost weathering can see the water in cracks expand as it freezes, widening the crack and causing further damage.
Protecting stone from damage
Even the ancient Romans understood the benefit of using a stonework sealant,often using olive oil to protect the surface, which would provide some protection, though it could permanently stain the rock. Through the Middle Ages, Europeans experimented with topical varnishes and sealants, made from an array of ingredients, which had varying levels of success. Technology has come a long way since then and today we have three broad types of stone sealers that can protect stone from damage and decay.
Which sealant to choose
A topical sealer is generally made from natural wax, polyurethanes or acrylics. They are quick to apply, provide good stain protection, but have a limited life expectancy, especially if used on highly trafficked floors. If the protected floor becomes wet, the sealer can cause the floor to become very slippery and are also impermeable, so do not allow the flow of water either direction. An impregnating sealer penetrates deep into the rock, bonding to the inside of the capillaries, preventing fluids or gases from penetrating, which makes for a very good long term solution. Penetrating sealers penetrate the surface of the stone and anchor the material to the rocks surface. They will generally not alter the look of the stone, though can alter the slip resistance and need replacing relatively often.
If you are looking for a solution on how to protect your stone from weather damage, or simply to prevent the growth of moss, mildew and algae on your stone surfaces, a quick Internet search will find local companies that can best advise on the solution that will work best for you.