I'm making a display of old newspaper clippings on canvas - what is best to paint over it to protect it ?

I've glued newspaper to gessoed canvas in the past using an acrylic gloss gel medium. (I use Golden brand regular gloss.) Water it down a little, and paint it on the surface of the canvas. Apply the newspaper clippings, and brush more watered-down medium over it. Carefully (and slowly) flatten with a wide-edge plastic putty knife, then let dry (it shouldn't take more than 20-30 minutes depending on the amount of medium you used). You can dab more medium on any areas that need extra coverage. When using this method, you can glue down the newspaper and protect the surface at the same time. Hope this helps and good luck with your project!

Usually if the artist who painted it was famous for some reason. However, sometimes they don't become really collectible until after they're dead. I would talk to someone in a reputable art auction house about this, to be honest.

I've heard of people using Shellac before. Whatever you choose to use, make sure you research and test before applying for real. Best of luck.

PVA glue watered down. it'll dry to form a plastic-like transparent film.