Do you ever walk through a cemetery and wonder why lichen colonies blanket some monuments, but not others? Or wonder how you can clean them off of your loved one’s stone? Well, here I list everything I’ve learned while working at Woodland about biological growths and how to clean them!
Every stone we’ve worked on so far has required multiple washes to clean the biological growths off the stone. While mud and most plant matter usually comes off with a spritz of water and a gentle scrub, some monuments need a more extensive cleaning with intervals of D2 and water.
D2 is a biological substance that we use to clean our stones. If you’ve been following our Instagram stories, it’s what we’ve been using in our dramatic before/after images that contrast blackened stones to stark white ones. D2 is the only substance we are comfortable using on monuments because it doesn’t have any destructive chemicals. (We aren’t sponsored by D2, I swear!)
Substances that are destructive to monuments includes salt; powders such as baby powder and flour; and household cleaners such as dish soap, window cleaner, or bathroom cleaner. Particulates of these substances can leach into the stone’s surface, and expand over time. This results in a faster deterioration of the stone – which is the opposite of what we want! On the contrary, D2 reacts to water and sunlight, to eat most biological growth and eventually bleach the stone closer to its original colour.
When a stone has extensive biological growth, precautions must be taken in removing them, otherwise you risk destroying the stone. When we clean a stone covered in lichen and moss, we spray it with D2 and water, and are easily able to scrub it off. However, if a plant with larger roots has attached to a stone, a few extra steps must be taken. If you pull out a plant with roots that reach deep into the stone, it has the potential to take out chunks of stone with it. Therefore, its so very important to cut the plant at the base, where it enters the stone, and let the roots die! Once the plant is cut from its roots, you can either let it die naturally, or spray it with D2 to quicken the process and prevent future plants from taking root in the same place. This will stop the plant from eating its way further into the stone, and keep the face of your precious monument intact.
Why do plants grow into stones, you may ask? Well, the older monuments we’ve been working on are primarily made from marble and sandstone. Marble has a very high calcium carbonate content, which plants find delicious. Sandstone can have this too, depending on the composition of that particular stone. Moreover, both these rock types are porous, which allows the roots to travel and expand. On the other hand, we have many granite monuments that are just as old as our lichen covered marble ones, but have no to little lichen and moss growth! This is because it’s difficult for plants to attach onto granite, especially when it’s polished!
Certain conditions foster better environments for growth than others. For example, monuments underneath trees accumulate various fallen biological matter, such as sap and leaves. They can also collect water pools from consistent dripping off of branches! All of these events can stain the monument, and allow for moss and lichen growth! We found a stark example of this in Section R the other day, when we found this Ann/Walker monument with two wide streaks of lichen growth on either side of the stone, but a nearly pristine center! This growth pattern exists because matter drips onto the monument from the tree above, but is divided by the peak at the centre of the monument before dripping down the sides. We chose not to clean the monument, because this amount of lichen will not harm the stone, and it will continue to grow like this until the tree is cut down.
Another way that biological matter negatively impacts our stones is by helping them to sink underground. Most commonly at Woodland Cemetery, grass clippings and dead leaves accumulate on top of tablets and fallen markers, which decomposes and eventually can cover the entire monument. The grass surrounding the monument can then grow onto it, either fully or partially, which makes it very difficult to identify that a marker has fallen there. Sometimes, the only way to find these markers is by randomly probing areas with our T-shaped rods, in hopes of hitting a marker. Sometimes we guess where to probe by searching for small slumps in the ground covered by damp leaf piles, or my looking for gaps in rows and columns of markers!
While we would prefer to locate and display all the sunken monuments, they are actually better preserved if left underground. The dirt protects them from pollution and substances that would otherwise blacken and deteriorate the stone! This is visible on the stones we’ve found partially underground and reset, as they have dark rings in the center from being exposed to harmful substances in the air! However, we think its important to raise the monuments regardless, so that the individual and their history are not forgotten.
And oftentimes, we leave moss and lichen on monuments. This is partially because we have to prioritize our time over many tasks and monuments, but also because this is something to be expected with any outdoor monument. Plant growth is natural to a rock’s life cycle, and sometimes, we should allow them to take that cycle.