Restoring a poster print using watercolour

Question

I recently bought a large second hand poster-size print. It has some slight damage to the sides and a strange stain line across one side (see photos).

I would really like to restore it if possible. I suspect the background was painted with watercolours. I have some experience painting with watercolours and thought maybe I could paint the missing pieces of background as best I could on separate paper and then stick the paper onto the print. (I would try to get the new paper as level with the print as possible but I don't know how I would do that yet.)

Does anyone have any advice on whether this is a good plan?

Or has anyone done something similar and able to share tips that would help?

^{Click on images for larger versions}

Answer 1

I don't have any pictures, but I once saw a "restored" print technique which amazed me. The damaged painting was valuable, so the owner didn't want to modify it directly. So he bought two appropriate sized frames and from their parts assembled a single frame with two sheets of protective glass.

Then with the painting behind a single sheet of glass, he painted his repairs on the glass. I suppose that the medium was very forgiving because any mistakes could be wiped away before they dry and reattempted as often as needed to get them right. Eventually, he had the look that he wanted. He then waited for all the paint to thoroughly dry.

At which point, he took the painting and glass out of the frame. Added the second sheet of glass in front of the painted one and reassembled his artwork.
In this way, the repairs on glass are themselves behind glass and the finished work is mostly indistinguishable from the original undamaged work.

Answer 2

I don’t think you will ever be able to satisfactorily repair a watercolor painting with this kind of damage. Gluing paper is risky, because you will never be able to match the texture and grain perfectly, which will make the repairs stand out even more. Matching the colors would similarly prove challenging -even for a professional.

I see two possibilities. Either use a gouache or acrylic to inpatient the damaged areas and distribute the repair across the painting in order to repair it with a new style. This would require a bit of skill, but is probably what I would do. (Below the green is kind of like what I mean.)

The other possibility is to take a very high quality photograph, repair the image digitally and have it archivally printed on canvas.