This edition of Caring for Your Collections blog posts comes from Binh-An Nguyen, a student in the Winterthur/University of Delaware Program in Art Conservation. Binh-An specializes in preventive conservation, which focuses on slowing down deterioration of objects by setting up good rules and habits for how to care for them.
Why should I clean my family’s gravestones?
There are many reasons why you may want to clean your family’s gravestones. Cleaning can make the names and inscriptions more easily readable so you can find the gravestone more easily, now and in the future. Cleaning them is also a way to show care or respect for loved ones who have passed.
What substances need to be cleaned from headstones?
Lichen, moss, or other living organisms that grown on gravestones are known as biogrowth. Biogrowth does not just exist on gravestones, it can exist on any surface with the right conditions—you may have noticed it on the roof of your house, for example.
Why is the biogrowth there?
Biogrowth loves moist environments. Rougher surfaces can cause moisture to be retained on the surface, creating ideal conditions for biofilms, lichens, etc. to grow. Gravestones with smoother, more polished finishes, on the other hand, may be less susceptible to biogrowth. Some gravestones use a combination of rough and smooth stones; you may notice that the biogrowth seems to prefer the rougher areas. Other environmental factors, such as location under a shady tree or in a rainy area, may also make a gravestone retain moisture, contributing to biogrowth.
What supplies do I need to clean a gravestone?
- D/2 biological cleaner: A quart-sized bottle can clean many medium-sized gravestones
- Clean water
- Two hand pump sprayers or spray bottles, one for clean water and one for diluted D/2 biological cleaning solution. A garden sprayer may be more useful if you are cleaning many gravestones in one day.
- Kitchen gloves
- Nylon scrub brushes
- Wooden or plastic popsicle sticks or spatulas
- Orvus, a nonionic surfactant (optional)
Do I need to ask for permission before cleaning a gravestone?
If the gravestone is for someone in your immediate family and located in a cemetery, it is a good idea to ask the cemetery for permission or let them know what you are doing.
If the gravestone is not for someone in your immediate family, make sure to also ask the immediate family or descendants of the person whose gravestone you want to clean.
How do I clean my family’s gravestones?
We recommend doing this on a warmer day/week. If the weather is too cold, the water used to clean/rinse the gravestone may freeze and create cracks in the stone. Cleaning outside in the cold may not be enjoyable for you either!
First, check the gravestone for any condition issues such as crumbling, separation of layers, “sugaring” (the stone crumbles when touched), etc., which may have affected the stability of the gravestone. If the gravestone is unstable, proceed with caution—cleaning it may cause further damage it. If it appears stable, then proceed to clean the gravestone using these steps:
- Trim any weeds from the base of the gravestone and brush away loose leaves or dirt.
- Wet the surface of the gravestone with clean water using the spray bottle or hand pump sprayer. Wetting the surface ensures that the cleaning solution stays on the surface and does not saturate the stone.
- Wearing kitchen gloves, apply a 1:1 solution of D/2 Biological Cleaner and clean water using a hand pump sprayer or spray bottle to saturate the surface. Allow the solution to sit for ~5 minutes and apply more as necessary to ensure the surface stays wet.
- Use a soft, nylon brush in slow circular motions to gently agitate the surface to allow the cleaning solution to saturate, and eventually remove, the biogrowth.
- Small amounts of Orvus can be applied directly to the stone and gently agitated with a soft, nylon brush to remove biofilm staining as needed. Rinse off the Orvus with clean water.
- Remove thicker lichen/biogrowth with wooden or plastic spatulas/popsicle sticks.
- Rinse the stone with clean water using a hand spray pump or spray bottle.
- Repeat steps 2–7 until desired cleaning level is achieved.
How often should I do this?
Repetitive cleaning can result in damaging the stone by making it unstable or wearing it down, so we recommend doing this no more than once a year. Additionally, using the biocide cleaning solution too often could result in biogrowth forming a resistance to the cleaner.
What are some things I should NOT do?
Do not use bleach; it can chemically interact with the stone and cause unintentional erosion/degradation.
Do not use metal scrapers or metal brushes to clean. They can scratch the stone surface. A good rule of thumb is “whatever is safe to clean the hood of your car is safe for the gravestone!”
Want to learn more about this topic? Sign up for a free consultation with our conservation staff and students to learn about how to take care of your family treasures. Be sure to read our other Caring for Your Collections blogs, Protecting and Preserving Family Heirlooms and Hazardous Objects.
Useful links:
- National Center for Preservation Technology and Training (NCPTT). 2011. “Best Practice Recommendations for Cleaning Government Issued Headstones.” Cemetery Conservators for United Standards. Last modified May 23, 2011.
- Prosoco. 2024. “How to Clean a Granite Headstone: 8 Steps for a Respectful Restoration.” Prosoco Hard Surface Care. Last modified March 28, 2024.