Summer is the time when many family researchers emerge from homes and libraries to visit cemeteries and look for family gravestones. As they find some stones in a less-than-perfect appearance, some may want to take action and clean the stone.

Cleaning gravestones brings up several questions — and not just about how to do it. There are other questions, such as: should the stone be cleaned at all, does the material of the stone dictate how to treat it, how often should you clean a particular stone, and should you clean a random stone of someone not in your family? Different experts and advocates in the field have differing opinions on some of these issues.

A physician takes an oath to first “do no harm,” and those words should also apply to someone setting out to clean gravestones. First look at the material the stone is made of. Some of the oldest stones are slate, shale, limestone, or sandstone. As they age, these often crack, crumble, flake, or scale. If is it an old hand-carved fieldstone, leave it alone. It is too old and fragile to be cleaned. Just gently sweep the dirt off of its surface with a very soft whisk-broom or brush, or blow the dust off. Take pictures of these stones in various angles of lighting and save the pictures for posterity because the stones won’t be here forever. If the grave is important to you, consider getting another more permanent marker to place on the grave as the fieldstone crumbles or becomes unreadable.

When deciding whether to clean a stone, first assess it to see if it is really dirty, or just aging naturally. An aging stone need not be cleaned because every act of cleaning causes a small amount of further erosion. Don’t clean a stone just for the sake of honoring the deceased. They are other ways to do that. Decide to clean a stone based on the dirt, grime, and organic growth that may be on it. Some types of soiling you might find on a stone are carbonaceous or sooty soiling, mainly from urban or industrial areas; organic growth including algae, fungi, lichens, and mosses; metallic, rusty, greasy, or oily stains; general dirt and grime; and efflorescence (salts).

Also consider the character of the overall cemetery when cleaning stones. The goal is not to make an old and aging stone “look like new” and stand out in an older cemetery, but to conserve the stone and protect it without doing further harm. There is nothing wrong with normally aging stones, and cleaning them for the sake of making them look like new would be similar to polishing the green patina off the Statue of Liberty just because it can be done.

One of the ethical questions that arises is do you have to get permission to clean the stone of someone not in your family, or to clean random stones that you think need cleaning? There are differences of opinion on this and possibly different policies across cemeteries. When cleaning a number of stones of people who are completely unrelated to you, it’s probably best to be a part of a cemetery restoration project that has an overall plan, the members have training and knowledge, the proper equipment and supplies are being used, and the group is following best practices to do no harm.

If you decide to clean a stone, start with the least aggressive method, which is water only and a gentle brush. Thoroughly wet and rinse the stone and clean it from the top down. Use nylon or nature fiber brushes and never wire brushes or pads. A toothbrush can be used for the indentations. Other tools that can be used are Q-tips, sponges, wooden spatulas, plastic scrapers, and rags. Moisten and then scrape off biological material. If you conclude that the stone needs more cleaning after using just water, keep in mind that you are going to have to buy special products to safely clean the stone. You will not be able to use your household cleaning products to do the job. There is a safe and tested product called D/2 Biological Solution that can be purchased on the Internet. And next week I’ll discuss a procedure for cleaning stones using other safe products that can be found locally.