How to get rid of illegal artificial paints on historical monuments?

Question

India is known for its historical monuments and Caves are essential part of them. While among them, almost all major tourist attractions are very well conserved and looked after, unfortunately some of them are yet to be admired at that level. I don't want to get into why the Archaeological Survey of India is so ignorant and careless about the majority of the historical places and overall conservation activities.

As a watchful tourist, I have seen plenty of places that are easily reachable and (hence?) spoiled by careless, ignorant people painting their names on the walls of the caves and forts and what not.

The good part is that the authorities are trying to reach out to frequent travelers, experienced mountaineers and archaeological experts to identify ways to prevent the damage, set new rules and encourage new ideas as to how to get the paint removed without damaging the structure and the rock.

Given the authority and opportunity, many of us are looking forward to contributing towards the initiative.

Have you known of trusted/proven ways to remove paint from a historically important surface without damaging it?

EDIT: Majority of the monuments I am referring to are about 400 to 1000 years old. I do understand that it is really not a span to sum up in two lines of course. But you know, that's the whole point about conserving them. If people and authorities do not care, its a huge asset to be ruined. Secondly, and more importantly the rock/stone surfaces I am referring to are Basalt.

Answer 1

When I've had to clean spray paint from remote destinations, we've used chemical paint removers in spray bottles and scrub brushes.

Do not do this on a historic site without permission from whoever manages it. There is a very good chance you will cause at least slight damage while removing the spray paint, and if you are careless, you can make the situation worse than it was when you started. The manager is the one who needs to decide whether the risk is worth it.

Materials and setup

Solvent: First, find out what type of surface you will be working on. Then find a paint removal chemical that is safe to use on that surface. Paint remover is a solvent, so you want to be sure it will only dissolve the paint, not a wall.

Brushes: Once you've got the solvent, get a few brushes and spray bottles. Make sure the bristles won't be dissolved by the solvent. Depending on the solvent, you'll probably need natural bristles. Metal might work, but it will cause much more wear on the historic site's structure. Brushes of different sizes and shapes are convenient if you've got an irregular surface, like natural rock.

Spray bottles and water: Fill half your spray bottles with solvent, and half with water. Then take extra water with you because you need enough to really rinse the solvent off the site when you are done. Figure on 2-3 times as much water as solvent, maybe more.

On site removal

Test Patch: Now it's time to take the materials to the site. Test the chemical on a tiny, hidden patch first. Spray the spot, let it sit for 15-20 minutes (or longer if the chemical's instructions say to), then wash it off with water. If the chemical hasn't damaged or discolored anything, you can use it (cleaning dirt is OK). Make sure you read the label of the chemical.

Now you are ready to start removing graffiti.

Do No Harm: First (and MOST important), think about the spot where you are working. What is the graffiti covering? If it is near or on top of an older painting, leave it alone. Same goes for if it is near writing, fabric, or anything else other than the material you've tested. You will do too much damage removing the graffiti. An expert can clean a single layer of paint off another painting, but you don't have the tools or the knowledge to do so. Do not even try. If you've got any question about whether you can safely remove the paint, leave it. Even if it takes another 50 years, someone with the proper skills can deal with it later, but if you cause extra damage, you make their job much harder, or impossible.

Scrub: If the paint is on a plain wall or surface, you can start removing it. Follow the instructions on the solvent. It will probably say to apply it, then leave it for about 10 minutes before removing it. The longer it sits, the better it dissolves the paint, and the less work you need to do. Scrub until the paint is gone. Rinse with the water as you go. Remove as much as is practical. There may still be flecks left, but they will be relatively faint.

Good luck and happy depainting!