Method One: Using Spit
Buy several cotton swabs. Using your spit to clean a work of art might seem both crazy and profane, but it's a method museum curators around the world use. Saliva has enough enzymes to break down dirt and grime, but not so much that it will damage the paint.[1] It'll take a lot of cotton swabs, though, so stock up with a full box.
Be aware that this method takes some patience — ask a museum intern
how many hours it can take to clean a large painting this way. (Hint:
It's more than 2.) But if you want to meticulously clean your painting
with almost zero risk of damage to the oils, this is the way to go.
Lightly wet the swab with your spit. You don't want the cotton soaking wet, but it should be wet enough to pick up any dirt particles with ease.
Gently dab the wet cotton over the painting. Don't move the cotton from side to side, but instead up and down in small, soft dotting motions. Aim to work around a square inch at a time.
Wet the other end of the swab. Once the first end has picked up so much dirt that it's no longer useful, move on to the other end. When that one is dirty, discard the swab and move on to the next.
Keep a glass of water handy. You should be working slowly enough that you don't feel like you're running out of saliva. Just in case your mouth does start to get dry, though, take a sip of water and wait a minute or two before going back for more spit.
Method Two: Using Bread
Buy a doughy bread. A loaf or two, or more, depending on the paintings and their size.
Work on a large white surface outside or inside in a controlled area.
Grab the center of the pieces of bread
Clear away crumbs. Use a soft brush, like a soft house paint brush, to remove the crumbs from the bread and clean the painting of the bread.
Keep up maintenance. Check for anything you may have
missed, and do this on a lighter scale on a regular basis to keep your
paintings in the best conditions.
Finished.
