I found this advice on line and thought I’d share it,
- Clean with a good quality eraser and then with a damp cotton ball to remove surface grime from the front.
- Immerse the whole piece is cold water to float off the surface print to separate it from its acidic backing. If there is no backing the water bath is a good idea as the wash will clean and flatten
- I let it dry thoroughly, light bleached the whole print for two hours on the front and 4 hours on the back and then let it dry again.
- Spot bleach any stained areas and then rinse it.
- While wet line with Japanese tissue using wheat starch paste.
- Let dry thoroughly.
- Humidify the print by sandwiching it between teflon sheets and placing it on top of a wet blotter and put a piece of glass on top to let it flatten out, and placed it under a lot of weight.
- Linen backing stage (not covered in detail)
- Inpaint the damaged areas that had pigment loss with reversible acrylics.
I’m going to try this myself on a poster shortly so that you can see the results. My biggest barrier ? drying time, I just hate to wait its always been the same from painting Airfix models onwards !