I feel like Ive been asked many times recently about clear coating art. I use clear coats in many of my abstract paintings. The best one Ive found, or my favorite one, is called table top Epoxi resin. It can be found in many hardware stores, but is pretty expensive. Ive found a great site were you can buy it much cheaper. http://www.uscomposites.com/kk121.html
Make sure you read all of the instructions very carefully before using this product though, it is the real deal.
One word of advice I can give, is to stir this stuff really slowly. Stiring it to fast will give it to many bubles(you may want this effect, so this is two words of advice), and it will make the epoxi look cloudy when you pour it.
It is also essential to have as perfect a 1:1 ratio as possible. Ive found a way to do this easily without as much mess. Get yourself a clear plastic container, a large yogurt container will work, its just harder to see through. Then using water and a measuring cup, pour different amounts into the container and mark the water level on the side of the container. View pic below;) This way you can pour the epoxi directly into the container you are mixing in, essentially making your own measuring cup/mixing cup/pouring cup all in one. Make sure you read all of the us composites website. They have a lot of great advice on it for you!
Here is my newest abstract with the resin poured on top of it. Sorry about the glare
