Humidity is a common term associated with warm seasons in Chicago. As temperatures rise during the spring and summer often do, so do precipitation and humidity levels. Unlike temperature, which fluctuates during the day and night, dew points tend to remain constant no matter what hour it is. High humidity levels tend to occur from early June to mid-September, resulting in a muggy three and a half month period. While some may view this warm and wet period as an excuse to get outside or an opportunity for clearer skin, this weather can also wreak havoc on stone, both indoors and out.
The main issue with constant humidity is that moisture eventually penetrates the stone itself. Areas of high concentration, such as backside soil or even concrete, push excess moisture to areas with lower concentrations, or the stone itself. This is extremely common among outdoor tiles placed directly on soil or stone installed on top of concrete. Excess moisture can cause both surface level and internal problems for the stone. The growth of algae and moss are common effects of humidity on stone, and fortunately, are fairly harmless as well. On the other hand, harsh effects still occur due to humidity. Rust and stone discoloration are examples of what moisture can do to stone once it penetrates the surface. Moisture can also deteriorate grouts, glues and any membranes that may protect the stone.
Depending on the extent of damage done to the stone, there are simple solutions to solve harm caused by moisture and humidity. Cleaners (alkaline) work well for the removal of surface level algae and moss on stone. The combination of a light film of water and a scrub brush is also a removal method. When it comes to rust and discoloration caused by deep moisture penetration, professional tools and solutions might be necessary in the attempt to restore the stone to its original state. See marble-institute.com or www.sungloss.com