What is the biodeterioration of stones?
Many micro-organisms (bacteria, fungi, algae) and lichens are able to grow on the stones of houses and monuments and can be responsible for damage. Not only do these damages have an unsightly appearance, but when there is insufficient protection, mosses, lichens, algae and fungi can appear.
How do the stones get contaminated?
The material is the physical support for biodeterioration and certain elements present in the stone matrix can be used as nutrients or, on the contrary, as growth inhibitors. The surface state is an aggravating factor during microbial colonisation. The porosity of the material is a factor to be taken into account as it accelerates biodeterioration. The more or less branched filaments of the mould allow the recovery of nutrients dissolved in the water trapped in the pores of the stone.
What are the consequences of the biodeterioration of the stones?
Biodeterioration of stone is defined as the unwanted damage to stone caused by micro-organisms, lichens and mosses. Biodeterioration processes lead to the loss of material properties, changes in composition or drops in mechanical characteristics. When stones are included in a structure, biodeterioration can pose a risk to the structure.
How to treat?
Four possibilities:
- It is possible to clean mechanically or with bleach. This will be very effective at the time. However, bleach will increase the porosity of the stone and make it more sensitive to frost.
- Pressurized water, on the other hand, can scatter spores and bury microorganisms in the porosity of the substrate.
- With these methods, there will be no subsequent protection. By using a quaternary ammonium like ORGANCIDE QC 50, the effect is deep down in the substrate to dislodge micro-organisms, and over time, as there is long-term protection.
- There is also biomineralization, which uses which uses the ability of certain soil microorganisms to produce calcium carbonate on the surface of the stone